Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) |
| 3 | * Internal non-public definitions that provide either classic |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 4 | * or preemptible semantics. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License as published by |
| 8 | * the Free Software Foundation; either version 2 of the License, or |
| 9 | * (at your option) any later version. |
| 10 | * |
| 11 | * This program is distributed in the hope that it will be useful, |
| 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | * GNU General Public License for more details. |
| 15 | * |
| 16 | * You should have received a copy of the GNU General Public License |
Paul E. McKenney | 87de1cf | 2013-12-03 10:02:52 -0800 | [diff] [blame] | 17 | * along with this program; if not, you can access it online at |
| 18 | * http://www.gnu.org/licenses/gpl-2.0.html. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 19 | * |
| 20 | * Copyright Red Hat, 2009 |
| 21 | * Copyright IBM Corporation, 2009 |
| 22 | * |
| 23 | * Author: Ingo Molnar <mingo@elte.hu> |
| 24 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
| 25 | */ |
| 26 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 27 | #include <linux/delay.h> |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 28 | #include <linux/gfp.h> |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 29 | #include <linux/oom.h> |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 30 | #include <linux/smpboot.h> |
Paul E. McKenney | 4102ada | 2013-10-08 20:23:47 -0700 | [diff] [blame] | 31 | #include "../time/tick-internal.h" |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 32 | |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 33 | #ifdef CONFIG_RCU_BOOST |
Paul E. McKenney | 61cfd09 | 2014-09-02 12:30:58 -0700 | [diff] [blame] | 34 | |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 35 | #include "../locking/rtmutex_common.h" |
Clark Williams | 21871d7 | 2014-09-12 21:21:09 -0500 | [diff] [blame] | 36 | |
Paul E. McKenney | 61cfd09 | 2014-09-02 12:30:58 -0700 | [diff] [blame] | 37 | /* |
| 38 | * Control variables for per-CPU and per-rcu_node kthreads. These |
| 39 | * handle all flavors of RCU. |
| 40 | */ |
| 41 | static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task); |
| 42 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status); |
| 43 | DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops); |
| 44 | DEFINE_PER_CPU(char, rcu_cpu_has_work); |
| 45 | |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 46 | #else /* #ifdef CONFIG_RCU_BOOST */ |
| 47 | |
| 48 | /* |
| 49 | * Some architectures do not define rt_mutexes, but if !CONFIG_RCU_BOOST, |
| 50 | * all uses are in dead code. Provide a definition to keep the compiler |
| 51 | * happy, but add WARN_ON_ONCE() to complain if used in the wrong place. |
| 52 | * This probably needs to be excluded from -rt builds. |
| 53 | */ |
| 54 | #define rt_mutex_owner(a) ({ WARN_ON_ONCE(1); NULL; }) |
| 55 | |
| 56 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 57 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 58 | #ifdef CONFIG_RCU_NOCB_CPU |
| 59 | static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */ |
| 60 | static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */ |
Paul Gortmaker | 1b0048a | 2012-12-20 13:19:22 -0800 | [diff] [blame] | 61 | static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 62 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ |
| 63 | |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 64 | /* |
| 65 | * Check the RCU kernel configuration parameters and print informative |
| 66 | * messages about anything out of the ordinary. If you like #ifdef, you |
| 67 | * will love this function. |
| 68 | */ |
| 69 | static void __init rcu_bootup_announce_oddness(void) |
| 70 | { |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 71 | if (IS_ENABLED(CONFIG_RCU_TRACE)) |
| 72 | pr_info("\tRCU debugfs-based tracing is enabled.\n"); |
Paul E. McKenney | 05c5df3 | 2015-04-20 14:27:43 -0700 | [diff] [blame] | 73 | if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) || |
| 74 | (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32)) |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 75 | pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", |
Paul E. McKenney | 05c5df3 | 2015-04-20 14:27:43 -0700 | [diff] [blame] | 76 | RCU_FANOUT); |
Paul E. McKenney | 7fa2700 | 2015-04-20 10:27:15 -0700 | [diff] [blame] | 77 | if (rcu_fanout_exact) |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 78 | pr_info("\tHierarchical RCU autobalancing is disabled.\n"); |
| 79 | if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ)) |
| 80 | pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n"); |
| 81 | if (IS_ENABLED(CONFIG_PROVE_RCU)) |
| 82 | pr_info("\tRCU lockdep checking is enabled.\n"); |
| 83 | if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_RUNNABLE)) |
| 84 | pr_info("\tRCU torture testing starts during boot.\n"); |
Alexander Gordeev | 4262169 | 2015-06-03 08:18:31 +0200 | [diff] [blame] | 85 | if (RCU_NUM_LVLS >= 4) |
| 86 | pr_info("\tFour(or more)-level hierarchy is enabled.\n"); |
Paul E. McKenney | 47d631a | 2015-04-21 09:12:13 -0700 | [diff] [blame] | 87 | if (RCU_FANOUT_LEAF != 16) |
Paul E. McKenney | a3bd2c0 | 2015-01-21 20:58:57 -0800 | [diff] [blame] | 88 | pr_info("\tBuild-time adjustment of leaf fanout to %d.\n", |
Paul E. McKenney | 47d631a | 2015-04-21 09:12:13 -0700 | [diff] [blame] | 89 | RCU_FANOUT_LEAF); |
| 90 | if (rcu_fanout_leaf != RCU_FANOUT_LEAF) |
Paul E. McKenney | 9a5739d | 2013-03-28 20:48:36 -0700 | [diff] [blame] | 91 | pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); |
Paul E. McKenney | cca6f39 | 2012-05-08 21:00:28 -0700 | [diff] [blame] | 92 | if (nr_cpu_ids != NR_CPUS) |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 93 | pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); |
Paul E. McKenney | ab6f5bd | 2015-01-21 16:58:06 -0800 | [diff] [blame] | 94 | if (IS_ENABLED(CONFIG_RCU_BOOST)) |
| 95 | pr_info("\tRCU kthread priority: %d.\n", kthread_prio); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 96 | } |
| 97 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 98 | #ifdef CONFIG_PREEMPT_RCU |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 99 | |
Steven Rostedt (Red Hat) | a41bfeb | 2013-07-12 17:00:28 -0400 | [diff] [blame] | 100 | RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu); |
Paul E. McKenney | b28a7c0 | 2015-03-04 07:39:27 -0800 | [diff] [blame] | 101 | static struct rcu_state *const rcu_state_p = &rcu_preempt_state; |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 102 | static struct rcu_data __percpu *const rcu_data_p = &rcu_preempt_data; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 103 | |
Paul E. McKenney | d19fb8d | 2014-10-31 12:56:16 -0700 | [diff] [blame] | 104 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp, |
| 105 | bool wake); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 106 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 107 | /* |
| 108 | * Tell them what RCU they are running. |
| 109 | */ |
Paul E. McKenney | 0e0fc1c | 2009-11-11 11:28:06 -0800 | [diff] [blame] | 110 | static void __init rcu_bootup_announce(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 111 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 112 | pr_info("Preemptible hierarchical RCU implementation.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 113 | rcu_bootup_announce_oddness(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 114 | } |
| 115 | |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 116 | /* Flags for rcu_preempt_ctxt_queue() decision table. */ |
| 117 | #define RCU_GP_TASKS 0x8 |
| 118 | #define RCU_EXP_TASKS 0x4 |
| 119 | #define RCU_GP_BLKD 0x2 |
| 120 | #define RCU_EXP_BLKD 0x1 |
| 121 | |
| 122 | /* |
| 123 | * Queues a task preempted within an RCU-preempt read-side critical |
| 124 | * section into the appropriate location within the ->blkd_tasks list, |
| 125 | * depending on the states of any ongoing normal and expedited grace |
| 126 | * periods. The ->gp_tasks pointer indicates which element the normal |
| 127 | * grace period is waiting on (NULL if none), and the ->exp_tasks pointer |
| 128 | * indicates which element the expedited grace period is waiting on (again, |
| 129 | * NULL if none). If a grace period is waiting on a given element in the |
| 130 | * ->blkd_tasks list, it also waits on all subsequent elements. Thus, |
| 131 | * adding a task to the tail of the list blocks any grace period that is |
| 132 | * already waiting on one of the elements. In contrast, adding a task |
| 133 | * to the head of the list won't block any grace period that is already |
| 134 | * waiting on one of the elements. |
| 135 | * |
| 136 | * This queuing is imprecise, and can sometimes make an ongoing grace |
| 137 | * period wait for a task that is not strictly speaking blocking it. |
| 138 | * Given the choice, we needlessly block a normal grace period rather than |
| 139 | * blocking an expedited grace period. |
| 140 | * |
| 141 | * Note that an endless sequence of expedited grace periods still cannot |
| 142 | * indefinitely postpone a normal grace period. Eventually, all of the |
| 143 | * fixed number of preempted tasks blocking the normal grace period that are |
| 144 | * not also blocking the expedited grace period will resume and complete |
| 145 | * their RCU read-side critical sections. At that point, the ->gp_tasks |
| 146 | * pointer will equal the ->exp_tasks pointer, at which point the end of |
| 147 | * the corresponding expedited grace period will also be the end of the |
| 148 | * normal grace period. |
| 149 | */ |
| 150 | static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp, |
| 151 | unsigned long flags) __releases(rnp->lock) |
| 152 | { |
| 153 | int blkd_state = (rnp->gp_tasks ? RCU_GP_TASKS : 0) + |
| 154 | (rnp->exp_tasks ? RCU_EXP_TASKS : 0) + |
| 155 | (rnp->qsmask & rdp->grpmask ? RCU_GP_BLKD : 0) + |
| 156 | (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0); |
| 157 | struct task_struct *t = current; |
| 158 | |
| 159 | /* |
| 160 | * Decide where to queue the newly blocked task. In theory, |
| 161 | * this could be an if-statement. In practice, when I tried |
| 162 | * that, it was quite messy. |
| 163 | */ |
| 164 | switch (blkd_state) { |
| 165 | case 0: |
| 166 | case RCU_EXP_TASKS: |
| 167 | case RCU_EXP_TASKS + RCU_GP_BLKD: |
| 168 | case RCU_GP_TASKS: |
| 169 | case RCU_GP_TASKS + RCU_EXP_TASKS: |
| 170 | |
| 171 | /* |
| 172 | * Blocking neither GP, or first task blocking the normal |
| 173 | * GP but not blocking the already-waiting expedited GP. |
| 174 | * Queue at the head of the list to avoid unnecessarily |
| 175 | * blocking the already-waiting GPs. |
| 176 | */ |
| 177 | list_add(&t->rcu_node_entry, &rnp->blkd_tasks); |
| 178 | break; |
| 179 | |
| 180 | case RCU_EXP_BLKD: |
| 181 | case RCU_GP_BLKD: |
| 182 | case RCU_GP_BLKD + RCU_EXP_BLKD: |
| 183 | case RCU_GP_TASKS + RCU_EXP_BLKD: |
| 184 | case RCU_GP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: |
| 185 | case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: |
| 186 | |
| 187 | /* |
| 188 | * First task arriving that blocks either GP, or first task |
| 189 | * arriving that blocks the expedited GP (with the normal |
| 190 | * GP already waiting), or a task arriving that blocks |
| 191 | * both GPs with both GPs already waiting. Queue at the |
| 192 | * tail of the list to avoid any GP waiting on any of the |
| 193 | * already queued tasks that are not blocking it. |
| 194 | */ |
| 195 | list_add_tail(&t->rcu_node_entry, &rnp->blkd_tasks); |
| 196 | break; |
| 197 | |
| 198 | case RCU_EXP_TASKS + RCU_EXP_BLKD: |
| 199 | case RCU_EXP_TASKS + RCU_GP_BLKD + RCU_EXP_BLKD: |
| 200 | case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_EXP_BLKD: |
| 201 | |
| 202 | /* |
| 203 | * Second or subsequent task blocking the expedited GP. |
| 204 | * The task either does not block the normal GP, or is the |
| 205 | * first task blocking the normal GP. Queue just after |
| 206 | * the first task blocking the expedited GP. |
| 207 | */ |
| 208 | list_add(&t->rcu_node_entry, rnp->exp_tasks); |
| 209 | break; |
| 210 | |
| 211 | case RCU_GP_TASKS + RCU_GP_BLKD: |
| 212 | case RCU_GP_TASKS + RCU_EXP_TASKS + RCU_GP_BLKD: |
| 213 | |
| 214 | /* |
| 215 | * Second or subsequent task blocking the normal GP. |
| 216 | * The task does not block the expedited GP. Queue just |
| 217 | * after the first task blocking the normal GP. |
| 218 | */ |
| 219 | list_add(&t->rcu_node_entry, rnp->gp_tasks); |
| 220 | break; |
| 221 | |
| 222 | default: |
| 223 | |
| 224 | /* Yet another exercise in excessive paranoia. */ |
| 225 | WARN_ON_ONCE(1); |
| 226 | break; |
| 227 | } |
| 228 | |
| 229 | /* |
| 230 | * We have now queued the task. If it was the first one to |
| 231 | * block either grace period, update the ->gp_tasks and/or |
| 232 | * ->exp_tasks pointers, respectively, to reference the newly |
| 233 | * blocked tasks. |
| 234 | */ |
| 235 | if (!rnp->gp_tasks && (blkd_state & RCU_GP_BLKD)) |
| 236 | rnp->gp_tasks = &t->rcu_node_entry; |
| 237 | if (!rnp->exp_tasks && (blkd_state & RCU_EXP_BLKD)) |
| 238 | rnp->exp_tasks = &t->rcu_node_entry; |
| 239 | raw_spin_unlock(&rnp->lock); |
| 240 | |
| 241 | /* |
| 242 | * Report the quiescent state for the expedited GP. This expedited |
| 243 | * GP should not be able to end until we report, so there should be |
| 244 | * no need to check for a subsequent expedited GP. (Though we are |
| 245 | * still in a quiescent state in any case.) |
| 246 | */ |
| 247 | if (blkd_state & RCU_EXP_BLKD && |
| 248 | t->rcu_read_unlock_special.b.exp_need_qs) { |
| 249 | t->rcu_read_unlock_special.b.exp_need_qs = false; |
| 250 | rcu_report_exp_rdp(rdp->rsp, rdp, true); |
| 251 | } else { |
| 252 | WARN_ON_ONCE(t->rcu_read_unlock_special.b.exp_need_qs); |
| 253 | } |
| 254 | local_irq_restore(flags); |
| 255 | } |
| 256 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 257 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 258 | * Record a preemptible-RCU quiescent state for the specified CPU. Note |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 259 | * that this just means that the task currently running on the CPU is |
| 260 | * not in a quiescent state. There might be any number of tasks blocked |
| 261 | * while in an RCU read-side critical section. |
Paul E. McKenney | 25502a6 | 2010-04-01 17:37:01 -0700 | [diff] [blame] | 262 | * |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 263 | * As with the other rcu_*_qs() functions, callers to this function |
| 264 | * must disable preemption. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 265 | */ |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 266 | static void rcu_preempt_qs(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 267 | { |
Paul E. McKenney | 5b74c45 | 2015-08-06 15:16:57 -0700 | [diff] [blame] | 268 | if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) { |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 269 | trace_rcu_grace_period(TPS("rcu_preempt"), |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 270 | __this_cpu_read(rcu_data_p->gpnum), |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 271 | TPS("cpuqs")); |
Paul E. McKenney | 5b74c45 | 2015-08-06 15:16:57 -0700 | [diff] [blame] | 272 | __this_cpu_write(rcu_data_p->cpu_no_qs.b.norm, false); |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 273 | barrier(); /* Coordinate with rcu_preempt_check_callbacks(). */ |
| 274 | current->rcu_read_unlock_special.b.need_qs = false; |
| 275 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 276 | } |
| 277 | |
| 278 | /* |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 279 | * We have entered the scheduler, and the current task might soon be |
| 280 | * context-switched away from. If this task is in an RCU read-side |
| 281 | * critical section, we will no longer be able to rely on the CPU to |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 282 | * record that fact, so we enqueue the task on the blkd_tasks list. |
| 283 | * The task will dequeue itself when it exits the outermost enclosing |
| 284 | * RCU read-side critical section. Therefore, the current grace period |
| 285 | * cannot be permitted to complete until the blkd_tasks list entries |
| 286 | * predating the current grace period drain, in other words, until |
| 287 | * rnp->gp_tasks becomes NULL. |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 288 | * |
| 289 | * Caller must disable preemption. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 290 | */ |
Paul E. McKenney | 38200cf | 2014-10-21 12:50:04 -0700 | [diff] [blame] | 291 | static void rcu_preempt_note_context_switch(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 292 | { |
| 293 | struct task_struct *t = current; |
Paul E. McKenney | c3422be | 2009-09-13 09:15:10 -0700 | [diff] [blame] | 294 | unsigned long flags; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 295 | struct rcu_data *rdp; |
| 296 | struct rcu_node *rnp; |
| 297 | |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 298 | if (t->rcu_read_lock_nesting > 0 && |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 299 | !t->rcu_read_unlock_special.b.blocked) { |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 300 | |
| 301 | /* Possibly blocking in an RCU read-side critical section. */ |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 302 | rdp = this_cpu_ptr(rcu_state_p->rda); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 303 | rnp = rdp->mynode; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 304 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | 6303b9c | 2013-12-11 13:59:10 -0800 | [diff] [blame] | 305 | smp_mb__after_unlock_lock(); |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 306 | t->rcu_read_unlock_special.b.blocked = true; |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 307 | t->rcu_blocked_node = rnp; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 308 | |
| 309 | /* |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 310 | * Verify the CPU's sanity, trace the preemption, and |
| 311 | * then queue the task as required based on the states |
| 312 | * of any ongoing and expedited grace periods. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 313 | */ |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 314 | WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0); |
Paul E. McKenney | e7d8842 | 2009-09-18 09:50:18 -0700 | [diff] [blame] | 315 | WARN_ON_ONCE(!list_empty(&t->rcu_node_entry)); |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 316 | trace_rcu_preempt_task(rdp->rsp->name, |
| 317 | t->pid, |
| 318 | (rnp->qsmask & rdp->grpmask) |
| 319 | ? rnp->gpnum |
| 320 | : rnp->gpnum + 1); |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 321 | rcu_preempt_ctxt_queue(rnp, rdp, flags); |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 322 | } else if (t->rcu_read_lock_nesting < 0 && |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 323 | t->rcu_read_unlock_special.s) { |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 324 | |
| 325 | /* |
| 326 | * Complete exit from RCU read-side critical section on |
| 327 | * behalf of preempted instance of __rcu_read_unlock(). |
| 328 | */ |
| 329 | rcu_read_unlock_special(t); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 330 | } |
| 331 | |
| 332 | /* |
| 333 | * Either we were not in an RCU read-side critical section to |
| 334 | * begin with, or we have now recorded that critical section |
| 335 | * globally. Either way, we can now note a quiescent state |
| 336 | * for this CPU. Again, if we were in an RCU read-side critical |
| 337 | * section, and if that critical section was blocking the current |
| 338 | * grace period, then the fact that the task has been enqueued |
| 339 | * means that we continue to block the current grace period. |
| 340 | */ |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 341 | rcu_preempt_qs(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 342 | } |
| 343 | |
| 344 | /* |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 345 | * Check for preempted RCU readers blocking the current grace period |
| 346 | * for the specified rcu_node structure. If the caller needs a reliable |
| 347 | * answer, it must hold the rcu_node's ->lock. |
| 348 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 349 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 350 | { |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 351 | return rnp->gp_tasks != NULL; |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 352 | } |
| 353 | |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 354 | /* |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 355 | * Advance a ->blkd_tasks-list pointer to the next entry, instead |
| 356 | * returning NULL if at the end of the list. |
| 357 | */ |
| 358 | static struct list_head *rcu_next_node_entry(struct task_struct *t, |
| 359 | struct rcu_node *rnp) |
| 360 | { |
| 361 | struct list_head *np; |
| 362 | |
| 363 | np = t->rcu_node_entry.next; |
| 364 | if (np == &rnp->blkd_tasks) |
| 365 | np = NULL; |
| 366 | return np; |
| 367 | } |
| 368 | |
| 369 | /* |
Paul E. McKenney | 8af3a5e | 2014-10-31 11:22:37 -0700 | [diff] [blame] | 370 | * Return true if the specified rcu_node structure has tasks that were |
| 371 | * preempted within an RCU read-side critical section. |
| 372 | */ |
| 373 | static bool rcu_preempt_has_tasks(struct rcu_node *rnp) |
| 374 | { |
| 375 | return !list_empty(&rnp->blkd_tasks); |
| 376 | } |
| 377 | |
| 378 | /* |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 379 | * Handle special cases during rcu_read_unlock(), such as needing to |
| 380 | * notify RCU core processing or task having blocked during the RCU |
| 381 | * read-side critical section. |
| 382 | */ |
Paul E. McKenney | 2a3fa84 | 2012-05-21 11:58:36 -0700 | [diff] [blame] | 383 | void rcu_read_unlock_special(struct task_struct *t) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 384 | { |
Paul E. McKenney | b6a932d | 2014-10-31 12:05:04 -0700 | [diff] [blame] | 385 | bool empty_exp; |
| 386 | bool empty_norm; |
| 387 | bool empty_exp_now; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 388 | unsigned long flags; |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 389 | struct list_head *np; |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 390 | bool drop_boost_mutex = false; |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 391 | struct rcu_data *rdp; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 392 | struct rcu_node *rnp; |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 393 | union rcu_special special; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 394 | |
| 395 | /* NMI handlers cannot block and cannot safely manipulate state. */ |
| 396 | if (in_nmi()) |
| 397 | return; |
| 398 | |
| 399 | local_irq_save(flags); |
| 400 | |
| 401 | /* |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 402 | * If RCU core is waiting for this CPU to exit its critical section, |
| 403 | * report the fact that it has exited. Because irqs are disabled, |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 404 | * t->rcu_read_unlock_special cannot change. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 405 | */ |
| 406 | special = t->rcu_read_unlock_special; |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 407 | if (special.b.need_qs) { |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 408 | rcu_preempt_qs(); |
Paul E. McKenney | c0135d0 | 2015-01-22 22:47:14 -0800 | [diff] [blame] | 409 | t->rcu_read_unlock_special.b.need_qs = false; |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 410 | if (!t->rcu_read_unlock_special.s) { |
Lai Jiangshan | 79a62f9 | 2013-10-30 04:13:22 -0700 | [diff] [blame] | 411 | local_irq_restore(flags); |
| 412 | return; |
| 413 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 414 | } |
| 415 | |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 416 | /* |
| 417 | * Respond to a request for an expedited grace period, but only if |
| 418 | * we were not preempted, meaning that we were running on the same |
| 419 | * CPU throughout. If we were preempted, the exp_need_qs flag |
| 420 | * would have been cleared at the time of the first preemption, |
| 421 | * and the quiescent state would be reported when we were dequeued. |
| 422 | */ |
| 423 | if (special.b.exp_need_qs) { |
| 424 | WARN_ON_ONCE(special.b.blocked); |
| 425 | t->rcu_read_unlock_special.b.exp_need_qs = false; |
| 426 | rdp = this_cpu_ptr(rcu_state_p->rda); |
| 427 | rcu_report_exp_rdp(rcu_state_p, rdp, true); |
| 428 | if (!t->rcu_read_unlock_special.s) { |
| 429 | local_irq_restore(flags); |
| 430 | return; |
| 431 | } |
| 432 | } |
| 433 | |
Lai Jiangshan | 79a62f9 | 2013-10-30 04:13:22 -0700 | [diff] [blame] | 434 | /* Hardware IRQ handlers cannot block, complain if they get here. */ |
Paul E. McKenney | d24209bb | 2015-01-21 15:26:03 -0800 | [diff] [blame] | 435 | if (in_irq() || in_serving_softirq()) { |
| 436 | lockdep_rcu_suspicious(__FILE__, __LINE__, |
| 437 | "rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n"); |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 438 | pr_alert("->rcu_read_unlock_special: %#x (b: %d, enq: %d nq: %d)\n", |
Paul E. McKenney | d24209bb | 2015-01-21 15:26:03 -0800 | [diff] [blame] | 439 | t->rcu_read_unlock_special.s, |
| 440 | t->rcu_read_unlock_special.b.blocked, |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 441 | t->rcu_read_unlock_special.b.exp_need_qs, |
Paul E. McKenney | d24209bb | 2015-01-21 15:26:03 -0800 | [diff] [blame] | 442 | t->rcu_read_unlock_special.b.need_qs); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 443 | local_irq_restore(flags); |
| 444 | return; |
| 445 | } |
| 446 | |
| 447 | /* Clean up if blocked during RCU read-side critical section. */ |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 448 | if (special.b.blocked) { |
| 449 | t->rcu_read_unlock_special.b.blocked = false; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 450 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 451 | /* |
Paul E. McKenney | 0a0ba1c | 2015-03-08 14:20:30 -0700 | [diff] [blame] | 452 | * Remove this task from the list it blocked on. The task |
| 453 | * now remains queued on the rcu_node corresponding to |
| 454 | * the CPU it first blocked on, so the first attempt to |
| 455 | * acquire the task's rcu_node's ->lock will succeed. |
| 456 | * Keep the loop and add a WARN_ON() out of sheer paranoia. |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 457 | */ |
| 458 | for (;;) { |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 459 | rnp = t->rcu_blocked_node; |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 460 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
Paul E. McKenney | 6303b9c | 2013-12-11 13:59:10 -0800 | [diff] [blame] | 461 | smp_mb__after_unlock_lock(); |
Paul E. McKenney | 8684896 | 2009-08-27 15:00:12 -0700 | [diff] [blame] | 462 | if (rnp == t->rcu_blocked_node) |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 463 | break; |
Paul E. McKenney | 0a0ba1c | 2015-03-08 14:20:30 -0700 | [diff] [blame] | 464 | WARN_ON_ONCE(1); |
Paul E. McKenney | 1304afb | 2010-02-22 17:05:02 -0800 | [diff] [blame] | 465 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 466 | } |
Paul E. McKenney | 74e871a | 2014-10-30 21:08:53 -0700 | [diff] [blame] | 467 | empty_norm = !rcu_preempt_blocked_readers_cgp(rnp); |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 468 | empty_exp = sync_rcu_preempt_exp_done(rnp); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 469 | smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */ |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 470 | np = rcu_next_node_entry(t, rnp); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 471 | list_del_init(&t->rcu_node_entry); |
Paul E. McKenney | 82e78d8 | 2011-08-04 07:55:34 -0700 | [diff] [blame] | 472 | t->rcu_blocked_node = NULL; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 473 | trace_rcu_unlock_preempted_task(TPS("rcu_preempt"), |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 474 | rnp->gpnum, t->pid); |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 475 | if (&t->rcu_node_entry == rnp->gp_tasks) |
| 476 | rnp->gp_tasks = np; |
| 477 | if (&t->rcu_node_entry == rnp->exp_tasks) |
| 478 | rnp->exp_tasks = np; |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 479 | if (IS_ENABLED(CONFIG_RCU_BOOST)) { |
| 480 | if (&t->rcu_node_entry == rnp->boost_tasks) |
| 481 | rnp->boost_tasks = np; |
| 482 | /* Snapshot ->boost_mtx ownership w/rnp->lock held. */ |
| 483 | drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t; |
| 484 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 485 | |
| 486 | /* |
| 487 | * If this was the last task on the current list, and if |
| 488 | * we aren't waiting on any CPUs, report the quiescent state. |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 489 | * Note that rcu_report_unblock_qs_rnp() releases rnp->lock, |
| 490 | * so we must take a snapshot of the expedited state. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 491 | */ |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 492 | empty_exp_now = sync_rcu_preempt_exp_done(rnp); |
Paul E. McKenney | 74e871a | 2014-10-30 21:08:53 -0700 | [diff] [blame] | 493 | if (!empty_norm && !rcu_preempt_blocked_readers_cgp(rnp)) { |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 494 | trace_rcu_quiescent_state_report(TPS("preempt_rcu"), |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 495 | rnp->gpnum, |
| 496 | 0, rnp->qsmask, |
| 497 | rnp->level, |
| 498 | rnp->grplo, |
| 499 | rnp->grphi, |
| 500 | !!rnp->gp_tasks); |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 501 | rcu_report_unblock_qs_rnp(rcu_state_p, rnp, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 502 | } else { |
Paul E. McKenney | d4c08f2 | 2011-06-25 06:36:56 -0700 | [diff] [blame] | 503 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | c701d5d | 2012-06-28 08:08:25 -0700 | [diff] [blame] | 504 | } |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 505 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 506 | /* Unboost if we were boosted. */ |
Paul E. McKenney | 727b705 | 2015-03-03 14:49:26 -0800 | [diff] [blame] | 507 | if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex) |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 508 | rt_mutex_unlock(&rnp->boost_mtx); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 509 | |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 510 | /* |
| 511 | * If this was the last task on the expedited lists, |
| 512 | * then we need to report up the rcu_node hierarchy. |
| 513 | */ |
Paul E. McKenney | 389abd4 | 2011-09-21 14:41:37 -0700 | [diff] [blame] | 514 | if (!empty_exp && empty_exp_now) |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 515 | rcu_report_exp_rnp(rcu_state_p, rnp, true); |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 516 | } else { |
| 517 | local_irq_restore(flags); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 518 | } |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 519 | } |
| 520 | |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 521 | /* |
| 522 | * Dump detailed information for all tasks blocking the current RCU |
| 523 | * grace period on the specified rcu_node structure. |
| 524 | */ |
| 525 | static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp) |
| 526 | { |
| 527 | unsigned long flags; |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 528 | struct task_struct *t; |
| 529 | |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 530 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | 5fd4dc0 | 2012-08-10 16:00:11 -0700 | [diff] [blame] | 531 | if (!rcu_preempt_blocked_readers_cgp(rnp)) { |
| 532 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 533 | return; |
| 534 | } |
Patrick Daly | 82efed0 | 2015-04-07 15:12:07 -0700 | [diff] [blame] | 535 | t = list_entry(rnp->gp_tasks->prev, |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 536 | struct task_struct, rcu_node_entry); |
| 537 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) |
| 538 | sched_show_task(t); |
| 539 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 540 | } |
| 541 | |
| 542 | /* |
| 543 | * Dump detailed information for all tasks blocking the current RCU |
| 544 | * grace period. |
| 545 | */ |
| 546 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 547 | { |
| 548 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 549 | |
| 550 | rcu_print_detail_task_stall_rnp(rnp); |
| 551 | rcu_for_each_leaf_node(rsp, rnp) |
| 552 | rcu_print_detail_task_stall_rnp(rnp); |
| 553 | } |
| 554 | |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 555 | static void rcu_print_task_stall_begin(struct rcu_node *rnp) |
| 556 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 557 | pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):", |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 558 | rnp->level, rnp->grplo, rnp->grphi); |
| 559 | } |
| 560 | |
| 561 | static void rcu_print_task_stall_end(void) |
| 562 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 563 | pr_cont("\n"); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 564 | } |
| 565 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 566 | /* |
| 567 | * Scan the current list of tasks blocked within RCU read-side critical |
| 568 | * sections, printing out the tid of each. |
| 569 | */ |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 570 | static int rcu_print_task_stall(struct rcu_node *rnp) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 571 | { |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 572 | struct task_struct *t; |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 573 | int ndetected = 0; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 574 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 575 | if (!rcu_preempt_blocked_readers_cgp(rnp)) |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 576 | return 0; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 577 | rcu_print_task_stall_begin(rnp); |
Patrick Daly | 82efed0 | 2015-04-07 15:12:07 -0700 | [diff] [blame] | 578 | t = list_entry(rnp->gp_tasks->prev, |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 579 | struct task_struct, rcu_node_entry); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 580 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 581 | pr_cont(" P%d", t->pid); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 582 | ndetected++; |
| 583 | } |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 584 | rcu_print_task_stall_end(); |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 585 | return ndetected; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 586 | } |
| 587 | |
Paul E. McKenney | 53d84e0 | 2010-08-10 14:28:53 -0700 | [diff] [blame] | 588 | /* |
Paul E. McKenney | 74611ec | 2015-08-18 10:20:43 -0700 | [diff] [blame] | 589 | * Scan the current list of tasks blocked within RCU read-side critical |
| 590 | * sections, printing out the tid of each that is blocking the current |
| 591 | * expedited grace period. |
| 592 | */ |
| 593 | static int rcu_print_task_exp_stall(struct rcu_node *rnp) |
| 594 | { |
| 595 | struct task_struct *t; |
| 596 | int ndetected = 0; |
| 597 | |
| 598 | if (!rnp->exp_tasks) |
| 599 | return 0; |
| 600 | t = list_entry(rnp->exp_tasks->prev, |
| 601 | struct task_struct, rcu_node_entry); |
| 602 | list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { |
| 603 | pr_cont(" P%d", t->pid); |
| 604 | ndetected++; |
| 605 | } |
| 606 | return ndetected; |
| 607 | } |
| 608 | |
| 609 | /* |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 610 | * Check that the list of blocked tasks for the newly completed grace |
| 611 | * period is in fact empty. It is a serious bug to complete a grace |
| 612 | * period that still has RCU readers blocked! This function must be |
| 613 | * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock |
| 614 | * must be held by the caller. |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 615 | * |
| 616 | * Also, if there are blocked tasks on the list, they automatically |
| 617 | * block the newly created grace period, so set up ->gp_tasks accordingly. |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 618 | */ |
| 619 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) |
| 620 | { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 621 | WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); |
Paul E. McKenney | 96e9202 | 2014-10-31 14:09:23 -0700 | [diff] [blame] | 622 | if (rcu_preempt_has_tasks(rnp)) |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 623 | rnp->gp_tasks = rnp->blkd_tasks.next; |
Paul E. McKenney | 28ecd58 | 2009-09-18 09:50:17 -0700 | [diff] [blame] | 624 | WARN_ON_ONCE(rnp->qsmask); |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 625 | } |
| 626 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 627 | /* |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 628 | * Check for a quiescent state from the current CPU. When a task blocks, |
| 629 | * the task is recorded in the corresponding CPU's rcu_node structure, |
| 630 | * which is checked elsewhere. |
| 631 | * |
| 632 | * Caller must disable hard irqs. |
| 633 | */ |
Paul E. McKenney | 86aea0e | 2014-10-21 08:12:00 -0700 | [diff] [blame] | 634 | static void rcu_preempt_check_callbacks(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 635 | { |
| 636 | struct task_struct *t = current; |
| 637 | |
| 638 | if (t->rcu_read_lock_nesting == 0) { |
Paul E. McKenney | 284a8c9 | 2014-08-14 16:38:46 -0700 | [diff] [blame] | 639 | rcu_preempt_qs(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 640 | return; |
| 641 | } |
Paul E. McKenney | 10f39bb | 2011-07-17 21:14:35 -0700 | [diff] [blame] | 642 | if (t->rcu_read_lock_nesting > 0 && |
Paul E. McKenney | 97c668b | 2015-08-06 11:31:51 -0700 | [diff] [blame] | 643 | __this_cpu_read(rcu_data_p->core_needs_qs) && |
Paul E. McKenney | 5b74c45 | 2015-08-06 15:16:57 -0700 | [diff] [blame] | 644 | __this_cpu_read(rcu_data_p->cpu_no_qs.b.norm)) |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 645 | t->rcu_read_unlock_special.b.need_qs = true; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 646 | } |
| 647 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 648 | #ifdef CONFIG_RCU_BOOST |
| 649 | |
Shaohua Li | 0922337 | 2011-06-14 13:26:25 +0800 | [diff] [blame] | 650 | static void rcu_preempt_do_callbacks(void) |
| 651 | { |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 652 | rcu_do_batch(rcu_state_p, this_cpu_ptr(rcu_data_p)); |
Shaohua Li | 0922337 | 2011-06-14 13:26:25 +0800 | [diff] [blame] | 653 | } |
| 654 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 655 | #endif /* #ifdef CONFIG_RCU_BOOST */ |
| 656 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 657 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 658 | * Queue a preemptible-RCU callback for invocation after a grace period. |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 659 | */ |
Boqun Feng | b6a4ae7 | 2015-07-29 13:29:38 +0800 | [diff] [blame] | 660 | void call_rcu(struct rcu_head *head, rcu_callback_t func) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 661 | { |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 662 | __call_rcu(head, func, rcu_state_p, -1, 0); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 663 | } |
| 664 | EXPORT_SYMBOL_GPL(call_rcu); |
| 665 | |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 666 | /** |
| 667 | * synchronize_rcu - wait until a grace period has elapsed. |
| 668 | * |
| 669 | * Control will return to the caller some time after a full grace |
| 670 | * period has elapsed, in other words after all currently executing RCU |
Paul E. McKenney | 77d8485 | 2010-07-08 17:38:59 -0700 | [diff] [blame] | 671 | * read-side critical sections have completed. Note, however, that |
| 672 | * upon return from synchronize_rcu(), the caller might well be executing |
| 673 | * concurrently with new RCU read-side critical sections that began while |
| 674 | * synchronize_rcu() was waiting. RCU read-side critical sections are |
| 675 | * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 676 | * |
| 677 | * See the description of synchronize_sched() for more detailed information |
| 678 | * on memory ordering guarantees. |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 679 | */ |
| 680 | void synchronize_rcu(void) |
| 681 | { |
Paul E. McKenney | f78f5b9 | 2015-06-18 15:50:02 -0700 | [diff] [blame] | 682 | RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || |
| 683 | lock_is_held(&rcu_lock_map) || |
| 684 | lock_is_held(&rcu_sched_lock_map), |
| 685 | "Illegal synchronize_rcu() in RCU read-side critical section"); |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 686 | if (!rcu_scheduler_active) |
| 687 | return; |
Paul E. McKenney | 5afff48 | 2015-02-18 16:39:09 -0800 | [diff] [blame] | 688 | if (rcu_gp_is_expedited()) |
Antti P Miettinen | 3705b88 | 2012-10-05 09:59:15 +0300 | [diff] [blame] | 689 | synchronize_rcu_expedited(); |
| 690 | else |
| 691 | wait_rcu_gp(call_rcu); |
Paul E. McKenney | 6ebb237 | 2009-11-22 08:53:50 -0800 | [diff] [blame] | 692 | } |
| 693 | EXPORT_SYMBOL_GPL(synchronize_rcu); |
| 694 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 695 | /* |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 696 | * Remote handler for smp_call_function_single(). If there is an |
| 697 | * RCU read-side critical section in effect, request that the |
| 698 | * next rcu_read_unlock() record the quiescent state up the |
| 699 | * ->expmask fields in the rcu_node tree. Otherwise, immediately |
| 700 | * report the quiescent state. |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 701 | */ |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 702 | static void sync_rcu_exp_handler(void *info) |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 703 | { |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 704 | struct rcu_data *rdp; |
| 705 | struct rcu_state *rsp = info; |
| 706 | struct task_struct *t = current; |
Paul E. McKenney | 8eb74b2 | 2015-02-13 10:52:28 -0800 | [diff] [blame] | 707 | |
| 708 | /* |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 709 | * Within an RCU read-side critical section, request that the next |
| 710 | * rcu_read_unlock() report. Unless this RCU read-side critical |
| 711 | * section has already blocked, in which case it is already set |
| 712 | * up for the expedited grace period to wait on it. |
Paul E. McKenney | 8eb74b2 | 2015-02-13 10:52:28 -0800 | [diff] [blame] | 713 | */ |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 714 | if (t->rcu_read_lock_nesting > 0 && |
| 715 | !t->rcu_read_unlock_special.b.blocked) { |
| 716 | t->rcu_read_unlock_special.b.exp_need_qs = true; |
Paul E. McKenney | 8eb74b2 | 2015-02-13 10:52:28 -0800 | [diff] [blame] | 717 | return; |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 718 | } |
Paul E. McKenney | 8eb74b2 | 2015-02-13 10:52:28 -0800 | [diff] [blame] | 719 | |
Paul E. McKenney | 8203d6d | 2015-08-02 13:53:17 -0700 | [diff] [blame] | 720 | /* |
| 721 | * We are either exiting an RCU read-side critical section (negative |
| 722 | * values of t->rcu_read_lock_nesting) or are not in one at all |
| 723 | * (zero value of t->rcu_read_lock_nesting). Or we are in an RCU |
| 724 | * read-side critical section that blocked before this expedited |
| 725 | * grace period started. Either way, we can immediately report |
| 726 | * the quiescent state. |
| 727 | */ |
| 728 | rdp = this_cpu_ptr(rsp->rda); |
| 729 | rcu_report_exp_rdp(rsp, rdp, true); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 730 | } |
| 731 | |
Paul E. McKenney | 236fefa | 2012-01-31 14:00:41 -0800 | [diff] [blame] | 732 | /** |
| 733 | * synchronize_rcu_expedited - Brute-force RCU grace period |
| 734 | * |
| 735 | * Wait for an RCU-preempt grace period, but expedite it. The basic |
| 736 | * idea is to invoke synchronize_sched_expedited() to push all the tasks to |
| 737 | * the ->blkd_tasks lists and wait for this list to drain. This consumes |
| 738 | * significant time on all CPUs and is unfriendly to real-time workloads, |
| 739 | * so is thus not recommended for any sort of common-case code. |
| 740 | * In fact, if you are using synchronize_rcu_expedited() in a loop, |
| 741 | * please restructure your code to batch your updates, and then Use a |
| 742 | * single synchronize_rcu() instead. |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 743 | */ |
| 744 | void synchronize_rcu_expedited(void) |
| 745 | { |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 746 | struct rcu_node *rnp; |
Paul E. McKenney | 29fd930 | 2015-06-25 19:03:16 -0700 | [diff] [blame] | 747 | struct rcu_node *rnp_unlock; |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 748 | struct rcu_state *rsp = rcu_state_p; |
Paul E. McKenney | 543c615 | 2015-06-25 15:52:50 -0700 | [diff] [blame] | 749 | unsigned long s; |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 750 | |
Paul E. McKenney | 543c615 | 2015-06-25 15:52:50 -0700 | [diff] [blame] | 751 | s = rcu_exp_gp_seq_snap(rsp); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 752 | |
Paul E. McKenney | 29fd930 | 2015-06-25 19:03:16 -0700 | [diff] [blame] | 753 | rnp_unlock = exp_funnel_lock(rsp, s); |
| 754 | if (rnp_unlock == NULL) |
| 755 | return; /* Someone else did our work for us. */ |
Paul E. McKenney | 1943c89 | 2012-07-30 17:19:25 -0700 | [diff] [blame] | 756 | |
Paul E. McKenney | 543c615 | 2015-06-25 15:52:50 -0700 | [diff] [blame] | 757 | rcu_exp_gp_seq_start(rsp); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 758 | |
Paul E. McKenney | b9585e9 | 2015-07-31 16:04:45 -0700 | [diff] [blame] | 759 | /* Initialize the rcu_node tree in preparation for the wait. */ |
Paul E. McKenney | dcdb880 | 2015-08-15 19:00:31 -0700 | [diff] [blame] | 760 | sync_rcu_exp_select_cpus(rsp, sync_rcu_exp_handler); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 761 | |
Paul E. McKenney | 12f5f52 | 2010-11-29 21:56:39 -0800 | [diff] [blame] | 762 | /* Wait for snapshotted ->blkd_tasks lists to drain. */ |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 763 | rnp = rcu_get_root(rsp); |
Paul E. McKenney | b08517c | 2015-08-18 12:17:29 -0700 | [diff] [blame] | 764 | synchronize_sched_expedited_wait(rsp); |
Paul E. McKenney | d9a3da0 | 2009-12-02 12:10:15 -0800 | [diff] [blame] | 765 | |
| 766 | /* Clean up and exit. */ |
Paul E. McKenney | 543c615 | 2015-06-25 15:52:50 -0700 | [diff] [blame] | 767 | rcu_exp_gp_seq_end(rsp); |
Paul E. McKenney | 29fd930 | 2015-06-25 19:03:16 -0700 | [diff] [blame] | 768 | mutex_unlock(&rnp_unlock->exp_funnel_mutex); |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 769 | } |
| 770 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
| 771 | |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 772 | /** |
| 773 | * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. |
Paul E. McKenney | f0a0e6f | 2012-10-23 13:47:01 -0700 | [diff] [blame] | 774 | * |
| 775 | * Note that this primitive does not necessarily wait for an RCU grace period |
| 776 | * to complete. For example, if there are no RCU callbacks queued anywhere |
| 777 | * in the system, then rcu_barrier() is within its rights to return |
| 778 | * immediately, without waiting for anything, much less an RCU grace period. |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 779 | */ |
| 780 | void rcu_barrier(void) |
| 781 | { |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 782 | _rcu_barrier(rcu_state_p); |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 783 | } |
| 784 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 785 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 786 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 787 | * Initialize preemptible RCU's state structures. |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 788 | */ |
| 789 | static void __init __rcu_init_preempt(void) |
| 790 | { |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 791 | rcu_init_one(rcu_state_p, rcu_data_p); |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 792 | } |
| 793 | |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 794 | /* |
| 795 | * Check for a task exiting while in a preemptible-RCU read-side |
| 796 | * critical section, clean up if so. No need to issue warnings, |
| 797 | * as debug_check_no_locks_held() already does this if lockdep |
| 798 | * is enabled. |
| 799 | */ |
| 800 | void exit_rcu(void) |
| 801 | { |
| 802 | struct task_struct *t = current; |
| 803 | |
| 804 | if (likely(list_empty(¤t->rcu_node_entry))) |
| 805 | return; |
| 806 | t->rcu_read_lock_nesting = 1; |
| 807 | barrier(); |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 808 | t->rcu_read_unlock_special.b.blocked = true; |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 809 | __rcu_read_unlock(); |
| 810 | } |
| 811 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 812 | #else /* #ifdef CONFIG_PREEMPT_RCU */ |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 813 | |
Paul E. McKenney | b28a7c0 | 2015-03-04 07:39:27 -0800 | [diff] [blame] | 814 | static struct rcu_state *const rcu_state_p = &rcu_sched_state; |
Paul E. McKenney | 2927a68 | 2015-03-04 07:53:04 -0800 | [diff] [blame] | 815 | static struct rcu_data __percpu *const rcu_data_p = &rcu_sched_data; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 816 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 817 | /* |
| 818 | * Tell them what RCU they are running. |
| 819 | */ |
Paul E. McKenney | 0e0fc1c | 2009-11-11 11:28:06 -0800 | [diff] [blame] | 820 | static void __init rcu_bootup_announce(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 821 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 822 | pr_info("Hierarchical RCU implementation.\n"); |
Paul E. McKenney | 26845c2 | 2010-04-13 14:19:23 -0700 | [diff] [blame] | 823 | rcu_bootup_announce_oddness(); |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 824 | } |
| 825 | |
| 826 | /* |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 827 | * Because preemptible RCU does not exist, we never have to check for |
| 828 | * CPUs being in quiescent states. |
| 829 | */ |
Paul E. McKenney | 38200cf | 2014-10-21 12:50:04 -0700 | [diff] [blame] | 830 | static void rcu_preempt_note_context_switch(void) |
Paul E. McKenney | cba6d0d | 2012-07-02 07:08:42 -0700 | [diff] [blame] | 831 | { |
| 832 | } |
| 833 | |
| 834 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 835 | * Because preemptible RCU does not exist, there are never any preempted |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 836 | * RCU readers. |
| 837 | */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 838 | static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp) |
Paul E. McKenney | fc2219d | 2009-09-23 09:50:41 -0700 | [diff] [blame] | 839 | { |
| 840 | return 0; |
| 841 | } |
| 842 | |
Paul E. McKenney | 8af3a5e | 2014-10-31 11:22:37 -0700 | [diff] [blame] | 843 | /* |
| 844 | * Because there is no preemptible RCU, there can be no readers blocked. |
| 845 | */ |
| 846 | static bool rcu_preempt_has_tasks(struct rcu_node *rnp) |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 847 | { |
Paul E. McKenney | 8af3a5e | 2014-10-31 11:22:37 -0700 | [diff] [blame] | 848 | return false; |
Paul E. McKenney | b668c9c | 2009-11-22 08:53:48 -0800 | [diff] [blame] | 849 | } |
| 850 | |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 851 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 852 | * Because preemptible RCU does not exist, we never have to check for |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 853 | * tasks blocked within RCU read-side critical sections. |
| 854 | */ |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 855 | static void rcu_print_detail_task_stall(struct rcu_state *rsp) |
| 856 | { |
| 857 | } |
| 858 | |
| 859 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 860 | * Because preemptible RCU does not exist, we never have to check for |
Paul E. McKenney | 1ed509a | 2010-02-22 17:05:05 -0800 | [diff] [blame] | 861 | * tasks blocked within RCU read-side critical sections. |
| 862 | */ |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 863 | static int rcu_print_task_stall(struct rcu_node *rnp) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 864 | { |
Paul E. McKenney | 9bc8b55 | 2011-08-13 13:31:47 -0700 | [diff] [blame] | 865 | return 0; |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 866 | } |
| 867 | |
Paul E. McKenney | 53d84e0 | 2010-08-10 14:28:53 -0700 | [diff] [blame] | 868 | /* |
Paul E. McKenney | 74611ec | 2015-08-18 10:20:43 -0700 | [diff] [blame] | 869 | * Because preemptible RCU does not exist, we never have to check for |
| 870 | * tasks blocked within RCU read-side critical sections that are |
| 871 | * blocking the current expedited grace period. |
| 872 | */ |
| 873 | static int rcu_print_task_exp_stall(struct rcu_node *rnp) |
| 874 | { |
| 875 | return 0; |
| 876 | } |
| 877 | |
| 878 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 879 | * Because there is no preemptible RCU, there can be no readers blocked, |
Paul E. McKenney | 49e2912 | 2009-09-18 09:50:19 -0700 | [diff] [blame] | 880 | * so there is no need to check for blocked tasks. So check only for |
| 881 | * bogus qsmask values. |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 882 | */ |
| 883 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) |
| 884 | { |
Paul E. McKenney | 49e2912 | 2009-09-18 09:50:19 -0700 | [diff] [blame] | 885 | WARN_ON_ONCE(rnp->qsmask); |
Paul E. McKenney | b0e165c | 2009-09-13 09:15:09 -0700 | [diff] [blame] | 886 | } |
| 887 | |
Paul E. McKenney | dd5d19b | 2009-08-27 14:58:16 -0700 | [diff] [blame] | 888 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 889 | * Because preemptible RCU does not exist, it never has any callbacks |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 890 | * to check. |
| 891 | */ |
Paul E. McKenney | 86aea0e | 2014-10-21 08:12:00 -0700 | [diff] [blame] | 892 | static void rcu_preempt_check_callbacks(void) |
Paul E. McKenney | f41d911 | 2009-08-22 13:56:52 -0700 | [diff] [blame] | 893 | { |
| 894 | } |
| 895 | |
| 896 | /* |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 897 | * Wait for an rcu-preempt grace period, but make it happen quickly. |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 898 | * But because preemptible RCU does not exist, map to rcu-sched. |
Paul E. McKenney | 019129d5 | 2009-10-14 10:15:56 -0700 | [diff] [blame] | 899 | */ |
| 900 | void synchronize_rcu_expedited(void) |
| 901 | { |
| 902 | synchronize_sched_expedited(); |
| 903 | } |
| 904 | EXPORT_SYMBOL_GPL(synchronize_rcu_expedited); |
| 905 | |
| 906 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 907 | * Because preemptible RCU does not exist, rcu_barrier() is just |
Paul E. McKenney | e74f4c4 | 2009-10-06 21:48:17 -0700 | [diff] [blame] | 908 | * another name for rcu_barrier_sched(). |
| 909 | */ |
| 910 | void rcu_barrier(void) |
| 911 | { |
| 912 | rcu_barrier_sched(); |
| 913 | } |
| 914 | EXPORT_SYMBOL_GPL(rcu_barrier); |
| 915 | |
| 916 | /* |
Paul E. McKenney | 6cc6879 | 2011-03-02 13:15:15 -0800 | [diff] [blame] | 917 | * Because preemptible RCU does not exist, it need not be initialized. |
Paul E. McKenney | 1eba8f8 | 2009-09-23 09:50:42 -0700 | [diff] [blame] | 918 | */ |
| 919 | static void __init __rcu_init_preempt(void) |
| 920 | { |
| 921 | } |
| 922 | |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 923 | /* |
| 924 | * Because preemptible RCU does not exist, tasks cannot possibly exit |
| 925 | * while in preemptible RCU read-side critical sections. |
| 926 | */ |
| 927 | void exit_rcu(void) |
| 928 | { |
| 929 | } |
| 930 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 931 | #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 932 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 933 | #ifdef CONFIG_RCU_BOOST |
| 934 | |
Peter Zijlstra | 1696a8b | 2013-10-31 18:18:19 +0100 | [diff] [blame] | 935 | #include "../locking/rtmutex_common.h" |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 936 | |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 937 | #ifdef CONFIG_RCU_TRACE |
| 938 | |
| 939 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) |
| 940 | { |
Paul E. McKenney | 96e9202 | 2014-10-31 14:09:23 -0700 | [diff] [blame] | 941 | if (!rcu_preempt_has_tasks(rnp)) |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 942 | rnp->n_balk_blkd_tasks++; |
| 943 | else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) |
| 944 | rnp->n_balk_exp_gp_tasks++; |
| 945 | else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) |
| 946 | rnp->n_balk_boost_tasks++; |
| 947 | else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) |
| 948 | rnp->n_balk_notblocked++; |
| 949 | else if (rnp->gp_tasks != NULL && |
Paul E. McKenney | a9f4793 | 2011-05-02 03:46:10 -0700 | [diff] [blame] | 950 | ULONG_CMP_LT(jiffies, rnp->boost_time)) |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 951 | rnp->n_balk_notyet++; |
| 952 | else |
| 953 | rnp->n_balk_nos++; |
| 954 | } |
| 955 | |
| 956 | #else /* #ifdef CONFIG_RCU_TRACE */ |
| 957 | |
| 958 | static void rcu_initiate_boost_trace(struct rcu_node *rnp) |
| 959 | { |
| 960 | } |
| 961 | |
| 962 | #endif /* #else #ifdef CONFIG_RCU_TRACE */ |
| 963 | |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 964 | static void rcu_wake_cond(struct task_struct *t, int status) |
| 965 | { |
| 966 | /* |
| 967 | * If the thread is yielding, only wake it when this |
| 968 | * is invoked from idle |
| 969 | */ |
| 970 | if (status != RCU_KTHREAD_YIELDING || is_idle_task(current)) |
| 971 | wake_up_process(t); |
| 972 | } |
| 973 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 974 | /* |
| 975 | * Carry out RCU priority boosting on the task indicated by ->exp_tasks |
| 976 | * or ->boost_tasks, advancing the pointer to the next task in the |
| 977 | * ->blkd_tasks list. |
| 978 | * |
| 979 | * Note that irqs must be enabled: boosting the task can block. |
| 980 | * Returns 1 if there are more tasks needing to be boosted. |
| 981 | */ |
| 982 | static int rcu_boost(struct rcu_node *rnp) |
| 983 | { |
| 984 | unsigned long flags; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 985 | struct task_struct *t; |
| 986 | struct list_head *tb; |
| 987 | |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 988 | if (READ_ONCE(rnp->exp_tasks) == NULL && |
| 989 | READ_ONCE(rnp->boost_tasks) == NULL) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 990 | return 0; /* Nothing left to boost. */ |
| 991 | |
| 992 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | 6303b9c | 2013-12-11 13:59:10 -0800 | [diff] [blame] | 993 | smp_mb__after_unlock_lock(); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 994 | |
| 995 | /* |
| 996 | * Recheck under the lock: all tasks in need of boosting |
| 997 | * might exit their RCU read-side critical sections on their own. |
| 998 | */ |
| 999 | if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL) { |
| 1000 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1001 | return 0; |
| 1002 | } |
| 1003 | |
| 1004 | /* |
| 1005 | * Preferentially boost tasks blocking expedited grace periods. |
| 1006 | * This cannot starve the normal grace periods because a second |
| 1007 | * expedited grace period must boost all blocked tasks, including |
| 1008 | * those blocking the pre-existing normal grace period. |
| 1009 | */ |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1010 | if (rnp->exp_tasks != NULL) { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1011 | tb = rnp->exp_tasks; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1012 | rnp->n_exp_boosts++; |
| 1013 | } else { |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1014 | tb = rnp->boost_tasks; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1015 | rnp->n_normal_boosts++; |
| 1016 | } |
| 1017 | rnp->n_tasks_boosted++; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1018 | |
| 1019 | /* |
| 1020 | * We boost task t by manufacturing an rt_mutex that appears to |
| 1021 | * be held by task t. We leave a pointer to that rt_mutex where |
| 1022 | * task t can find it, and task t will release the mutex when it |
| 1023 | * exits its outermost RCU read-side critical section. Then |
| 1024 | * simply acquiring this artificial rt_mutex will boost task |
| 1025 | * t's priority. (Thanks to tglx for suggesting this approach!) |
| 1026 | * |
| 1027 | * Note that task t must acquire rnp->lock to remove itself from |
| 1028 | * the ->blkd_tasks list, which it will do from exit() if from |
| 1029 | * nowhere else. We therefore are guaranteed that task t will |
| 1030 | * stay around at least until we drop rnp->lock. Note that |
| 1031 | * rnp->lock also resolves races between our priority boosting |
| 1032 | * and task t's exiting its outermost RCU read-side critical |
| 1033 | * section. |
| 1034 | */ |
| 1035 | t = container_of(tb, struct task_struct, rcu_node_entry); |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 1036 | rt_mutex_init_proxy_locked(&rnp->boost_mtx, t); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1037 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | abaa93d | 2014-06-12 13:30:25 -0700 | [diff] [blame] | 1038 | /* Lock only for side effect: boosts task t's priority. */ |
| 1039 | rt_mutex_lock(&rnp->boost_mtx); |
| 1040 | rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1041 | |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1042 | return READ_ONCE(rnp->exp_tasks) != NULL || |
| 1043 | READ_ONCE(rnp->boost_tasks) != NULL; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1044 | } |
| 1045 | |
| 1046 | /* |
Paul E. McKenney | bc17ea1 | 2015-06-06 08:11:43 -0700 | [diff] [blame] | 1047 | * Priority-boosting kthread, one per leaf rcu_node. |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1048 | */ |
| 1049 | static int rcu_boost_kthread(void *arg) |
| 1050 | { |
| 1051 | struct rcu_node *rnp = (struct rcu_node *)arg; |
| 1052 | int spincnt = 0; |
| 1053 | int more2boost; |
| 1054 | |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1055 | trace_rcu_utilization(TPS("Start boost kthread@init")); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1056 | for (;;) { |
Paul E. McKenney | d71df90 | 2011-03-29 17:48:28 -0700 | [diff] [blame] | 1057 | rnp->boost_kthread_status = RCU_KTHREAD_WAITING; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1058 | trace_rcu_utilization(TPS("End boost kthread@rcu_wait")); |
Peter Zijlstra | 08bca60 | 2011-05-20 16:06:29 -0700 | [diff] [blame] | 1059 | rcu_wait(rnp->boost_tasks || rnp->exp_tasks); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1060 | trace_rcu_utilization(TPS("Start boost kthread@rcu_wait")); |
Paul E. McKenney | d71df90 | 2011-03-29 17:48:28 -0700 | [diff] [blame] | 1061 | rnp->boost_kthread_status = RCU_KTHREAD_RUNNING; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1062 | more2boost = rcu_boost(rnp); |
| 1063 | if (more2boost) |
| 1064 | spincnt++; |
| 1065 | else |
| 1066 | spincnt = 0; |
| 1067 | if (spincnt > 10) { |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1068 | rnp->boost_kthread_status = RCU_KTHREAD_YIELDING; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1069 | trace_rcu_utilization(TPS("End boost kthread@rcu_yield")); |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1070 | schedule_timeout_interruptible(2); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1071 | trace_rcu_utilization(TPS("Start boost kthread@rcu_yield")); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1072 | spincnt = 0; |
| 1073 | } |
| 1074 | } |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1075 | /* NOTREACHED */ |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1076 | trace_rcu_utilization(TPS("End boost kthread@notreached")); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1077 | return 0; |
| 1078 | } |
| 1079 | |
| 1080 | /* |
| 1081 | * Check to see if it is time to start boosting RCU readers that are |
| 1082 | * blocking the current grace period, and, if so, tell the per-rcu_node |
| 1083 | * kthread to start boosting them. If there is an expedited grace |
| 1084 | * period in progress, it is always time to boost. |
| 1085 | * |
Paul E. McKenney | b065a85 | 2012-08-01 15:57:54 -0700 | [diff] [blame] | 1086 | * The caller must hold rnp->lock, which this function releases. |
| 1087 | * The ->boost_kthread_task is immortal, so we don't need to worry |
| 1088 | * about it going away. |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1089 | */ |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1090 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
Pranith Kumar | 615e41c | 2014-06-11 16:39:40 -0400 | [diff] [blame] | 1091 | __releases(rnp->lock) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1092 | { |
| 1093 | struct task_struct *t; |
| 1094 | |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1095 | if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { |
| 1096 | rnp->n_balk_exp_gp_tasks++; |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1097 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1098 | return; |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1099 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1100 | if (rnp->exp_tasks != NULL || |
| 1101 | (rnp->gp_tasks != NULL && |
| 1102 | rnp->boost_tasks == NULL && |
| 1103 | rnp->qsmask == 0 && |
| 1104 | ULONG_CMP_GE(jiffies, rnp->boost_time))) { |
| 1105 | if (rnp->exp_tasks == NULL) |
| 1106 | rnp->boost_tasks = rnp->gp_tasks; |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1107 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1108 | t = rnp->boost_kthread_task; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1109 | if (t) |
| 1110 | rcu_wake_cond(t, rnp->boost_kthread_status); |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1111 | } else { |
Paul E. McKenney | 0ea1f2e | 2011-02-22 13:42:43 -0800 | [diff] [blame] | 1112 | rcu_initiate_boost_trace(rnp); |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1113 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1114 | } |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1115 | } |
| 1116 | |
Paul E. McKenney | 0f962a5 | 2011-04-14 12:13:53 -0700 | [diff] [blame] | 1117 | /* |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1118 | * Wake up the per-CPU kthread to invoke RCU callbacks. |
| 1119 | */ |
| 1120 | static void invoke_rcu_callbacks_kthread(void) |
| 1121 | { |
| 1122 | unsigned long flags; |
| 1123 | |
| 1124 | local_irq_save(flags); |
| 1125 | __this_cpu_write(rcu_cpu_has_work, 1); |
Shaohua Li | 1eb5212 | 2011-06-16 16:02:54 -0700 | [diff] [blame] | 1126 | if (__this_cpu_read(rcu_cpu_kthread_task) != NULL && |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1127 | current != __this_cpu_read(rcu_cpu_kthread_task)) { |
| 1128 | rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task), |
| 1129 | __this_cpu_read(rcu_cpu_kthread_status)); |
| 1130 | } |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1131 | local_irq_restore(flags); |
| 1132 | } |
| 1133 | |
| 1134 | /* |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1135 | * Is the current CPU running the RCU-callbacks kthread? |
| 1136 | * Caller must have preemption disabled. |
| 1137 | */ |
| 1138 | static bool rcu_is_callbacks_kthread(void) |
| 1139 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1140 | return __this_cpu_read(rcu_cpu_kthread_task) == current; |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1141 | } |
| 1142 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1143 | #define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000) |
| 1144 | |
| 1145 | /* |
| 1146 | * Do priority-boost accounting for the start of a new grace period. |
| 1147 | */ |
| 1148 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
| 1149 | { |
| 1150 | rnp->boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES; |
| 1151 | } |
| 1152 | |
| 1153 | /* |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1154 | * Create an RCU-boost kthread for the specified node if one does not |
| 1155 | * already exist. We only create this kthread for preemptible RCU. |
| 1156 | * Returns zero if all is well, a negated errno otherwise. |
| 1157 | */ |
Paul Gortmaker | 49fb4c6 | 2013-06-19 14:52:21 -0400 | [diff] [blame] | 1158 | static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 1159 | struct rcu_node *rnp) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1160 | { |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1161 | int rnp_index = rnp - &rsp->node[0]; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1162 | unsigned long flags; |
| 1163 | struct sched_param sp; |
| 1164 | struct task_struct *t; |
| 1165 | |
Paul E. McKenney | e63c887 | 2015-03-03 12:56:43 -0800 | [diff] [blame] | 1166 | if (rcu_state_p != rsp) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1167 | return 0; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1168 | |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 1169 | if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0) |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1170 | return 0; |
| 1171 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1172 | rsp->boost = 1; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1173 | if (rnp->boost_kthread_task != NULL) |
| 1174 | return 0; |
| 1175 | t = kthread_create(rcu_boost_kthread, (void *)rnp, |
Mike Galbraith | 5b61b0b | 2011-08-19 11:39:11 -0700 | [diff] [blame] | 1176 | "rcub/%d", rnp_index); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1177 | if (IS_ERR(t)) |
| 1178 | return PTR_ERR(t); |
| 1179 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | 6303b9c | 2013-12-11 13:59:10 -0800 | [diff] [blame] | 1180 | smp_mb__after_unlock_lock(); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1181 | rnp->boost_kthread_task = t; |
| 1182 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Clark Williams | 21871d7 | 2014-09-12 21:21:09 -0500 | [diff] [blame] | 1183 | sp.sched_priority = kthread_prio; |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1184 | sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); |
Paul E. McKenney | 9a43273 | 2011-05-30 20:38:55 -0700 | [diff] [blame] | 1185 | wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */ |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1186 | return 0; |
| 1187 | } |
| 1188 | |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1189 | static void rcu_kthread_do_work(void) |
| 1190 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1191 | rcu_do_batch(&rcu_sched_state, this_cpu_ptr(&rcu_sched_data)); |
| 1192 | rcu_do_batch(&rcu_bh_state, this_cpu_ptr(&rcu_bh_data)); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1193 | rcu_preempt_do_callbacks(); |
| 1194 | } |
| 1195 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1196 | static void rcu_cpu_kthread_setup(unsigned int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1197 | { |
| 1198 | struct sched_param sp; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1199 | |
Clark Williams | 21871d7 | 2014-09-12 21:21:09 -0500 | [diff] [blame] | 1200 | sp.sched_priority = kthread_prio; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1201 | sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1202 | } |
| 1203 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1204 | static void rcu_cpu_kthread_park(unsigned int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1205 | { |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1206 | per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU; |
| 1207 | } |
| 1208 | |
| 1209 | static int rcu_cpu_kthread_should_run(unsigned int cpu) |
| 1210 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1211 | return __this_cpu_read(rcu_cpu_has_work); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1212 | } |
| 1213 | |
| 1214 | /* |
| 1215 | * Per-CPU kernel thread that invokes RCU callbacks. This replaces the |
Paul E. McKenney | e0f2306 | 2011-06-21 01:29:39 -0700 | [diff] [blame] | 1216 | * RCU softirq used in flavors and configurations of RCU that do not |
| 1217 | * support RCU priority boosting. |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1218 | */ |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1219 | static void rcu_cpu_kthread(unsigned int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1220 | { |
Christoph Lameter | c9d4b0a | 2013-08-31 13:34:10 -0700 | [diff] [blame] | 1221 | unsigned int *statusp = this_cpu_ptr(&rcu_cpu_kthread_status); |
| 1222 | char work, *workp = this_cpu_ptr(&rcu_cpu_has_work); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1223 | int spincnt; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1224 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1225 | for (spincnt = 0; spincnt < 10; spincnt++) { |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1226 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_wait")); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1227 | local_bh_disable(); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1228 | *statusp = RCU_KTHREAD_RUNNING; |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1229 | this_cpu_inc(rcu_cpu_kthread_loops); |
| 1230 | local_irq_disable(); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1231 | work = *workp; |
| 1232 | *workp = 0; |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1233 | local_irq_enable(); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1234 | if (work) |
| 1235 | rcu_kthread_do_work(); |
| 1236 | local_bh_enable(); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1237 | if (*workp == 0) { |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1238 | trace_rcu_utilization(TPS("End CPU kthread@rcu_wait")); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1239 | *statusp = RCU_KTHREAD_WAITING; |
| 1240 | return; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1241 | } |
| 1242 | } |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1243 | *statusp = RCU_KTHREAD_YIELDING; |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1244 | trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield")); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1245 | schedule_timeout_interruptible(2); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 1246 | trace_rcu_utilization(TPS("End CPU kthread@rcu_yield")); |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1247 | *statusp = RCU_KTHREAD_WAITING; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1248 | } |
| 1249 | |
| 1250 | /* |
| 1251 | * Set the per-rcu_node kthread's affinity to cover all CPUs that are |
| 1252 | * served by the rcu_node in question. The CPU hotplug lock is still |
| 1253 | * held, so the value of rnp->qsmaskinit will be stable. |
| 1254 | * |
| 1255 | * We don't include outgoingcpu in the affinity set, use -1 if there is |
| 1256 | * no outgoing CPU. If there are no CPUs left in the affinity set, |
| 1257 | * this function allows the kthread to execute on any CPU. |
| 1258 | */ |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1259 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1260 | { |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1261 | struct task_struct *t = rnp->boost_kthread_task; |
Paul E. McKenney | 0aa04b0 | 2015-01-23 21:52:37 -0800 | [diff] [blame] | 1262 | unsigned long mask = rcu_rnp_online_cpus(rnp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1263 | cpumask_var_t cm; |
| 1264 | int cpu; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1265 | |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1266 | if (!t) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1267 | return; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1268 | if (!zalloc_cpumask_var(&cm, GFP_KERNEL)) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1269 | return; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1270 | for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) |
| 1271 | if ((mask & 0x1) && cpu != outgoingcpu) |
| 1272 | cpumask_set_cpu(cpu, cm); |
Paul E. McKenney | 5d0b024 | 2014-11-10 08:07:08 -0800 | [diff] [blame] | 1273 | if (cpumask_weight(cm) == 0) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1274 | cpumask_setall(cm); |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1275 | set_cpus_allowed_ptr(t, cm); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1276 | free_cpumask_var(cm); |
| 1277 | } |
| 1278 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1279 | static struct smp_hotplug_thread rcu_cpu_thread_spec = { |
| 1280 | .store = &rcu_cpu_kthread_task, |
| 1281 | .thread_should_run = rcu_cpu_kthread_should_run, |
| 1282 | .thread_fn = rcu_cpu_kthread, |
| 1283 | .thread_comm = "rcuc/%u", |
| 1284 | .setup = rcu_cpu_kthread_setup, |
| 1285 | .park = rcu_cpu_kthread_park, |
| 1286 | }; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1287 | |
| 1288 | /* |
Paul E. McKenney | 9386c0b | 2014-07-13 12:00:53 -0700 | [diff] [blame] | 1289 | * Spawn boost kthreads -- called as soon as the scheduler is running. |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1290 | */ |
Paul E. McKenney | 9386c0b | 2014-07-13 12:00:53 -0700 | [diff] [blame] | 1291 | static void __init rcu_spawn_boost_kthreads(void) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1292 | { |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1293 | struct rcu_node *rnp; |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1294 | int cpu; |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1295 | |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1296 | for_each_possible_cpu(cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1297 | per_cpu(rcu_cpu_has_work, cpu) = 0; |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1298 | BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec)); |
Paul E. McKenney | 3e9f5c7 | 2014-11-03 18:15:17 -0800 | [diff] [blame] | 1299 | rcu_for_each_leaf_node(rcu_state_p, rnp) |
| 1300 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1301 | } |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1302 | |
Paul Gortmaker | 49fb4c6 | 2013-06-19 14:52:21 -0400 | [diff] [blame] | 1303 | static void rcu_prepare_kthreads(int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1304 | { |
Uma Sharma | e534165 | 2014-03-23 22:32:09 -0700 | [diff] [blame] | 1305 | struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1306 | struct rcu_node *rnp = rdp->mynode; |
| 1307 | |
| 1308 | /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */ |
Paul E. McKenney | 62ab707 | 2012-07-16 10:42:38 +0000 | [diff] [blame] | 1309 | if (rcu_scheduler_fully_active) |
Uma Sharma | e534165 | 2014-03-23 22:32:09 -0700 | [diff] [blame] | 1310 | (void)rcu_spawn_one_boost_kthread(rcu_state_p, rnp); |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1311 | } |
| 1312 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1313 | #else /* #ifdef CONFIG_RCU_BOOST */ |
| 1314 | |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1315 | static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) |
Pranith Kumar | 615e41c | 2014-06-11 16:39:40 -0400 | [diff] [blame] | 1316 | __releases(rnp->lock) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1317 | { |
Paul E. McKenney | 1217ed1 | 2011-05-04 21:43:49 -0700 | [diff] [blame] | 1318 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1319 | } |
| 1320 | |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1321 | static void invoke_rcu_callbacks_kthread(void) |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1322 | { |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1323 | WARN_ON_ONCE(1); |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1324 | } |
| 1325 | |
Paul E. McKenney | dff1672 | 2011-11-29 15:57:13 -0800 | [diff] [blame] | 1326 | static bool rcu_is_callbacks_kthread(void) |
| 1327 | { |
| 1328 | return false; |
| 1329 | } |
| 1330 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1331 | static void rcu_preempt_boost_start_gp(struct rcu_node *rnp) |
| 1332 | { |
| 1333 | } |
| 1334 | |
Thomas Gleixner | 5d01bbd | 2012-07-16 10:42:35 +0000 | [diff] [blame] | 1335 | static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1336 | { |
| 1337 | } |
| 1338 | |
Paul E. McKenney | 9386c0b | 2014-07-13 12:00:53 -0700 | [diff] [blame] | 1339 | static void __init rcu_spawn_boost_kthreads(void) |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1340 | { |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1341 | } |
Paul E. McKenney | b0d3041 | 2011-07-10 15:57:35 -0700 | [diff] [blame] | 1342 | |
Paul Gortmaker | 49fb4c6 | 2013-06-19 14:52:21 -0400 | [diff] [blame] | 1343 | static void rcu_prepare_kthreads(int cpu) |
Paul E. McKenney | f8b7fc6 | 2011-06-16 08:26:32 -0700 | [diff] [blame] | 1344 | { |
| 1345 | } |
| 1346 | |
Paul E. McKenney | 27f4d28 | 2011-02-07 12:47:15 -0800 | [diff] [blame] | 1347 | #endif /* #else #ifdef CONFIG_RCU_BOOST */ |
| 1348 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1349 | #if !defined(CONFIG_RCU_FAST_NO_HZ) |
| 1350 | |
| 1351 | /* |
| 1352 | * Check to see if any future RCU-related work will need to be done |
| 1353 | * by the current CPU, even if none need be done immediately, returning |
| 1354 | * 1 if so. This function is part of the RCU implementation; it is -not- |
| 1355 | * an exported member of the RCU API. |
| 1356 | * |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1357 | * Because we not have RCU_FAST_NO_HZ, just check whether this CPU needs |
| 1358 | * any flavor of RCU. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1359 | */ |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1360 | int rcu_needs_cpu(u64 basemono, u64 *nextevt) |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1361 | { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1362 | *nextevt = KTIME_MAX; |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1363 | return IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) |
| 1364 | ? 0 : rcu_cpu_has_callbacks(NULL); |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1365 | } |
| 1366 | |
| 1367 | /* |
| 1368 | * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up |
| 1369 | * after it. |
| 1370 | */ |
Paul E. McKenney | 8fa7845d | 2014-10-22 15:07:37 -0700 | [diff] [blame] | 1371 | static void rcu_cleanup_after_idle(void) |
Paul E. McKenney | 7cb9249 | 2011-11-28 12:28:34 -0800 | [diff] [blame] | 1372 | { |
| 1373 | } |
| 1374 | |
| 1375 | /* |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1376 | * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n, |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1377 | * is nothing. |
| 1378 | */ |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1379 | static void rcu_prepare_for_idle(void) |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1380 | { |
| 1381 | } |
| 1382 | |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1383 | /* |
| 1384 | * Don't bother keeping a running count of the number of RCU callbacks |
| 1385 | * posted because CONFIG_RCU_FAST_NO_HZ=n. |
| 1386 | */ |
| 1387 | static void rcu_idle_count_callbacks_posted(void) |
| 1388 | { |
| 1389 | } |
| 1390 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1391 | #else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
| 1392 | |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1393 | /* |
| 1394 | * This code is invoked when a CPU goes idle, at which point we want |
| 1395 | * to have the CPU do everything required for RCU so that it can enter |
| 1396 | * the energy-efficient dyntick-idle mode. This is handled by a |
| 1397 | * state machine implemented by rcu_prepare_for_idle() below. |
| 1398 | * |
| 1399 | * The following three proprocessor symbols control this state machine: |
| 1400 | * |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1401 | * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted |
| 1402 | * to sleep in dyntick-idle mode with RCU callbacks pending. This |
| 1403 | * is sized to be roughly one RCU grace period. Those energy-efficiency |
| 1404 | * benchmarkers who might otherwise be tempted to set this to a large |
| 1405 | * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your |
| 1406 | * system. And if you are -that- concerned about energy efficiency, |
| 1407 | * just power the system down and be done with it! |
Paul E. McKenney | 778d250 | 2012-01-10 14:13:24 -0800 | [diff] [blame] | 1408 | * RCU_IDLE_LAZY_GP_DELAY gives the number of jiffies that a CPU is |
| 1409 | * permitted to sleep in dyntick-idle mode with only lazy RCU |
| 1410 | * callbacks pending. Setting this too high can OOM your system. |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1411 | * |
| 1412 | * The values below work well in practice. If future workloads require |
| 1413 | * adjustment, they can be converted into kernel config parameters, though |
| 1414 | * making the state machine smarter might be a better option. |
| 1415 | */ |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1416 | #define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */ |
Paul E. McKenney | 778d250 | 2012-01-10 14:13:24 -0800 | [diff] [blame] | 1417 | #define RCU_IDLE_LAZY_GP_DELAY (6 * HZ) /* Roughly six seconds. */ |
Paul E. McKenney | f23f7fa | 2011-11-30 15:41:14 -0800 | [diff] [blame] | 1418 | |
Paul E. McKenney | 5e44ce3 | 2012-12-12 12:35:29 -0800 | [diff] [blame] | 1419 | static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY; |
| 1420 | module_param(rcu_idle_gp_delay, int, 0644); |
| 1421 | static int rcu_idle_lazy_gp_delay = RCU_IDLE_LAZY_GP_DELAY; |
| 1422 | module_param(rcu_idle_lazy_gp_delay, int, 0644); |
| 1423 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1424 | /* |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1425 | * Try to advance callbacks for all flavors of RCU on the current CPU, but |
| 1426 | * only if it has been awhile since the last time we did so. Afterwards, |
| 1427 | * if there are any callbacks ready for immediate invocation, return true. |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1428 | */ |
Paul E. McKenney | f1f399d | 2013-11-17 21:08:07 -0800 | [diff] [blame] | 1429 | static bool __maybe_unused rcu_try_advance_all_cbs(void) |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1430 | { |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1431 | bool cbs_ready = false; |
| 1432 | struct rcu_data *rdp; |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1433 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1434 | struct rcu_node *rnp; |
| 1435 | struct rcu_state *rsp; |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1436 | |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1437 | /* Exit early if we advanced recently. */ |
| 1438 | if (jiffies == rdtp->last_advance_all) |
Pranith Kumar | d0bc90f | 2014-07-08 18:26:13 -0400 | [diff] [blame] | 1439 | return false; |
Paul E. McKenney | c229828 | 2013-08-25 21:20:47 -0700 | [diff] [blame] | 1440 | rdtp->last_advance_all = jiffies; |
| 1441 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1442 | for_each_rcu_flavor(rsp) { |
| 1443 | rdp = this_cpu_ptr(rsp->rda); |
| 1444 | rnp = rdp->mynode; |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1445 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1446 | /* |
| 1447 | * Don't bother checking unless a grace period has |
| 1448 | * completed since we last checked and there are |
| 1449 | * callbacks not yet ready to invoke. |
| 1450 | */ |
Paul E. McKenney | e3663b1 | 2014-12-08 20:26:55 -0800 | [diff] [blame] | 1451 | if ((rdp->completed != rnp->completed || |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1452 | unlikely(READ_ONCE(rdp->gpwrap))) && |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1453 | rdp->nxttail[RCU_DONE_TAIL] != rdp->nxttail[RCU_NEXT_TAIL]) |
Paul E. McKenney | 470716f | 2013-03-19 11:32:11 -0700 | [diff] [blame] | 1454 | note_gp_changes(rsp, rdp); |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1455 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1456 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| 1457 | cbs_ready = true; |
| 1458 | } |
| 1459 | return cbs_ready; |
Paul E. McKenney | 486e259 | 2012-01-06 14:11:30 -0800 | [diff] [blame] | 1460 | } |
| 1461 | |
| 1462 | /* |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1463 | * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready |
| 1464 | * to invoke. If the CPU has callbacks, try to advance them. Tell the |
| 1465 | * caller to set the timeout based on whether or not there are non-lazy |
| 1466 | * callbacks. |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1467 | * |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1468 | * The caller must have disabled interrupts. |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1469 | */ |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1470 | int rcu_needs_cpu(u64 basemono, u64 *nextevt) |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1471 | { |
Paul E. McKenney | aa6da51 | 2014-10-21 13:23:08 -0700 | [diff] [blame] | 1472 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1473 | unsigned long dj; |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1474 | |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1475 | if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL)) { |
Linus Torvalds | 43224b9 | 2015-06-22 18:57:44 -0700 | [diff] [blame] | 1476 | *nextevt = KTIME_MAX; |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1477 | return 0; |
| 1478 | } |
| 1479 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1480 | /* Snapshot to detect later posting of non-lazy callback. */ |
| 1481 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; |
| 1482 | |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1483 | /* If no callbacks, RCU doesn't need the CPU. */ |
Paul E. McKenney | aa6da51 | 2014-10-21 13:23:08 -0700 | [diff] [blame] | 1484 | if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1485 | *nextevt = KTIME_MAX; |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1486 | return 0; |
| 1487 | } |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1488 | |
| 1489 | /* Attempt to advance callbacks. */ |
| 1490 | if (rcu_try_advance_all_cbs()) { |
| 1491 | /* Some ready to invoke, so initiate later invocation. */ |
| 1492 | invoke_rcu_core(); |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1493 | return 1; |
| 1494 | } |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1495 | rdtp->last_accelerate = jiffies; |
| 1496 | |
| 1497 | /* Request timer delay depending on laziness, and round. */ |
Paul E. McKenney | 6faf728 | 2013-05-13 06:53:37 -0700 | [diff] [blame] | 1498 | if (!rdtp->all_lazy) { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1499 | dj = round_up(rcu_idle_gp_delay + jiffies, |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1500 | rcu_idle_gp_delay) - jiffies; |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1501 | } else { |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1502 | dj = round_jiffies(rcu_idle_lazy_gp_delay + jiffies) - jiffies; |
Paul E. McKenney | e84c48a | 2012-06-04 20:45:10 -0700 | [diff] [blame] | 1503 | } |
Thomas Gleixner | c1ad348 | 2015-04-14 21:08:58 +0000 | [diff] [blame] | 1504 | *nextevt = basemono + dj * TICK_NSEC; |
Paul E. McKenney | aa9b1630 | 2012-05-10 16:41:44 -0700 | [diff] [blame] | 1505 | return 0; |
| 1506 | } |
| 1507 | |
| 1508 | /* |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1509 | * Prepare a CPU for idle from an RCU perspective. The first major task |
| 1510 | * is to sense whether nohz mode has been enabled or disabled via sysfs. |
| 1511 | * The second major task is to check to see if a non-lazy callback has |
| 1512 | * arrived at a CPU that previously had only lazy callbacks. The third |
| 1513 | * major task is to accelerate (that is, assign grace-period numbers to) |
| 1514 | * any recently arrived callbacks. |
Paul E. McKenney | aea1b35 | 2011-11-02 06:54:54 -0700 | [diff] [blame] | 1515 | * |
| 1516 | * The caller must have disabled interrupts. |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1517 | */ |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1518 | static void rcu_prepare_for_idle(void) |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1519 | { |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 1520 | bool needwake; |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1521 | struct rcu_data *rdp; |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1522 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1523 | struct rcu_node *rnp; |
| 1524 | struct rcu_state *rsp; |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1525 | int tne; |
| 1526 | |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1527 | if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL)) |
| 1528 | return; |
| 1529 | |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1530 | /* Handle nohz enablement switches conservatively. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1531 | tne = READ_ONCE(tick_nohz_active); |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1532 | if (tne != rdtp->tick_nohz_enabled_snap) { |
Paul E. McKenney | aa6da51 | 2014-10-21 13:23:08 -0700 | [diff] [blame] | 1533 | if (rcu_cpu_has_callbacks(NULL)) |
Paul E. McKenney | 9d2ad24 | 2012-06-24 10:15:02 -0700 | [diff] [blame] | 1534 | invoke_rcu_core(); /* force nohz to see update. */ |
| 1535 | rdtp->tick_nohz_enabled_snap = tne; |
| 1536 | return; |
| 1537 | } |
| 1538 | if (!tne) |
| 1539 | return; |
Paul E. McKenney | f511fc6 | 2012-03-15 12:16:26 -0700 | [diff] [blame] | 1540 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1541 | /* If this is a no-CBs CPU, no callbacks, just return. */ |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1542 | if (rcu_is_nocb_cpu(smp_processor_id())) |
Paul E. McKenney | 9a0c6fe | 2012-06-28 12:33:51 -0700 | [diff] [blame] | 1543 | return; |
Paul E. McKenney | 9a0c6fe | 2012-06-28 12:33:51 -0700 | [diff] [blame] | 1544 | |
Paul E. McKenney | 3084f2f | 2011-11-22 17:07:11 -0800 | [diff] [blame] | 1545 | /* |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1546 | * If a non-lazy callback arrived at a CPU having only lazy |
| 1547 | * callbacks, invoke RCU core for the side-effect of recalculating |
| 1548 | * idle duration on re-entry to idle. |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1549 | */ |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1550 | if (rdtp->all_lazy && |
| 1551 | rdtp->nonlazy_posted != rdtp->nonlazy_posted_snap) { |
Paul E. McKenney | c337f8f | 2013-09-05 17:02:11 -0700 | [diff] [blame] | 1552 | rdtp->all_lazy = false; |
| 1553 | rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; |
Paul E. McKenney | a46e089 | 2011-06-15 15:47:09 -0700 | [diff] [blame] | 1554 | invoke_rcu_core(); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1555 | return; |
| 1556 | } |
| 1557 | |
| 1558 | /* |
| 1559 | * If we have not yet accelerated this jiffy, accelerate all |
| 1560 | * callbacks on this CPU. |
| 1561 | */ |
| 1562 | if (rdtp->last_accelerate == jiffies) |
| 1563 | return; |
| 1564 | rdtp->last_accelerate = jiffies; |
| 1565 | for_each_rcu_flavor(rsp) { |
Paul E. McKenney | 198bbf8 | 2014-10-22 15:03:43 -0700 | [diff] [blame] | 1566 | rdp = this_cpu_ptr(rsp->rda); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1567 | if (!*rdp->nxttail[RCU_DONE_TAIL]) |
| 1568 | continue; |
| 1569 | rnp = rdp->mynode; |
| 1570 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
Paul E. McKenney | 6303b9c | 2013-12-11 13:59:10 -0800 | [diff] [blame] | 1571 | smp_mb__after_unlock_lock(); |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 1572 | needwake = rcu_accelerate_cbs(rsp, rnp, rdp); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1573 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 1574 | if (needwake) |
| 1575 | rcu_gp_kthread_wake(rsp); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1576 | } |
| 1577 | } |
| 1578 | |
| 1579 | /* |
| 1580 | * Clean up for exit from idle. Attempt to advance callbacks based on |
| 1581 | * any grace periods that elapsed while the CPU was idle, and if any |
| 1582 | * callbacks are now ready to invoke, initiate invocation. |
| 1583 | */ |
Paul E. McKenney | 8fa7845d | 2014-10-22 15:07:37 -0700 | [diff] [blame] | 1584 | static void rcu_cleanup_after_idle(void) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1585 | { |
Paul E. McKenney | 3382adb | 2015-03-04 15:41:24 -0800 | [diff] [blame] | 1586 | if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) || |
| 1587 | rcu_is_nocb_cpu(smp_processor_id())) |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1588 | return; |
Paul E. McKenney | 7a497c9 | 2013-08-22 18:16:16 -0700 | [diff] [blame] | 1589 | if (rcu_try_advance_all_cbs()) |
| 1590 | invoke_rcu_core(); |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1591 | } |
| 1592 | |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1593 | /* |
Paul E. McKenney | 98248a0 | 2012-05-03 15:38:10 -0700 | [diff] [blame] | 1594 | * Keep a running count of the number of non-lazy callbacks posted |
| 1595 | * on this CPU. This running counter (which is never decremented) allows |
| 1596 | * rcu_prepare_for_idle() to detect when something out of the idle loop |
| 1597 | * posts a callback, even if an equal number of callbacks are invoked. |
| 1598 | * Of course, callbacks should only be posted from within a trace event |
| 1599 | * designed to be called from idle or from within RCU_NONIDLE(). |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1600 | */ |
| 1601 | static void rcu_idle_count_callbacks_posted(void) |
| 1602 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1603 | __this_cpu_add(rcu_dynticks.nonlazy_posted, 1); |
Paul E. McKenney | c57afe8 | 2012-02-28 11:02:21 -0800 | [diff] [blame] | 1604 | } |
| 1605 | |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1606 | /* |
| 1607 | * Data for flushing lazy RCU callbacks at OOM time. |
| 1608 | */ |
| 1609 | static atomic_t oom_callback_count; |
| 1610 | static DECLARE_WAIT_QUEUE_HEAD(oom_callback_wq); |
| 1611 | |
| 1612 | /* |
| 1613 | * RCU OOM callback -- decrement the outstanding count and deliver the |
| 1614 | * wake-up if we are the last one. |
| 1615 | */ |
| 1616 | static void rcu_oom_callback(struct rcu_head *rhp) |
| 1617 | { |
| 1618 | if (atomic_dec_and_test(&oom_callback_count)) |
| 1619 | wake_up(&oom_callback_wq); |
| 1620 | } |
| 1621 | |
| 1622 | /* |
| 1623 | * Post an rcu_oom_notify callback on the current CPU if it has at |
| 1624 | * least one lazy callback. This will unnecessarily post callbacks |
| 1625 | * to CPUs that already have a non-lazy callback at the end of their |
| 1626 | * callback list, but this is an infrequent operation, so accept some |
| 1627 | * extra overhead to keep things simple. |
| 1628 | */ |
| 1629 | static void rcu_oom_notify_cpu(void *unused) |
| 1630 | { |
| 1631 | struct rcu_state *rsp; |
| 1632 | struct rcu_data *rdp; |
| 1633 | |
| 1634 | for_each_rcu_flavor(rsp) { |
Christoph Lameter | fa07a58 | 2014-04-15 12:20:12 -0700 | [diff] [blame] | 1635 | rdp = raw_cpu_ptr(rsp->rda); |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1636 | if (rdp->qlen_lazy != 0) { |
| 1637 | atomic_inc(&oom_callback_count); |
| 1638 | rsp->call(&rdp->oom_head, rcu_oom_callback); |
| 1639 | } |
| 1640 | } |
| 1641 | } |
| 1642 | |
| 1643 | /* |
| 1644 | * If low on memory, ensure that each CPU has a non-lazy callback. |
| 1645 | * This will wake up CPUs that have only lazy callbacks, in turn |
| 1646 | * ensuring that they free up the corresponding memory in a timely manner. |
| 1647 | * Because an uncertain amount of memory will be freed in some uncertain |
| 1648 | * timeframe, we do not claim to have freed anything. |
| 1649 | */ |
| 1650 | static int rcu_oom_notify(struct notifier_block *self, |
| 1651 | unsigned long notused, void *nfreed) |
| 1652 | { |
| 1653 | int cpu; |
| 1654 | |
| 1655 | /* Wait for callbacks from earlier instance to complete. */ |
| 1656 | wait_event(oom_callback_wq, atomic_read(&oom_callback_count) == 0); |
Paul E. McKenney | 78e4bc3 | 2013-09-24 15:04:06 -0700 | [diff] [blame] | 1657 | smp_mb(); /* Ensure callback reuse happens after callback invocation. */ |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1658 | |
| 1659 | /* |
| 1660 | * Prevent premature wakeup: ensure that all increments happen |
| 1661 | * before there is a chance of the counter reaching zero. |
| 1662 | */ |
| 1663 | atomic_set(&oom_callback_count, 1); |
| 1664 | |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1665 | for_each_online_cpu(cpu) { |
| 1666 | smp_call_function_single(cpu, rcu_oom_notify_cpu, NULL, 1); |
Paul E. McKenney | bde6c3a | 2014-07-01 11:26:57 -0700 | [diff] [blame] | 1667 | cond_resched_rcu_qs(); |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1668 | } |
Paul E. McKenney | b626c1b | 2012-06-11 17:39:43 -0700 | [diff] [blame] | 1669 | |
| 1670 | /* Unconditionally decrement: no need to wake ourselves up. */ |
| 1671 | atomic_dec(&oom_callback_count); |
| 1672 | |
| 1673 | return NOTIFY_OK; |
| 1674 | } |
| 1675 | |
| 1676 | static struct notifier_block rcu_oom_nb = { |
| 1677 | .notifier_call = rcu_oom_notify |
| 1678 | }; |
| 1679 | |
| 1680 | static int __init rcu_register_oom_notifier(void) |
| 1681 | { |
| 1682 | register_oom_notifier(&rcu_oom_nb); |
| 1683 | return 0; |
| 1684 | } |
| 1685 | early_initcall(rcu_register_oom_notifier); |
| 1686 | |
Paul E. McKenney | 8bd93a2 | 2010-02-22 17:04:59 -0800 | [diff] [blame] | 1687 | #endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */ |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1688 | |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1689 | #ifdef CONFIG_RCU_FAST_NO_HZ |
| 1690 | |
| 1691 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) |
| 1692 | { |
Paul E. McKenney | 5955f7e | 2012-05-09 12:07:05 -0700 | [diff] [blame] | 1693 | struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1694 | unsigned long nlpd = rdtp->nonlazy_posted - rdtp->nonlazy_posted_snap; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1695 | |
Paul E. McKenney | c0f4dfd | 2012-12-28 11:30:36 -0800 | [diff] [blame] | 1696 | sprintf(cp, "last_accelerate: %04lx/%04lx, nonlazy_posted: %ld, %c%c", |
| 1697 | rdtp->last_accelerate & 0xffff, jiffies & 0xffff, |
| 1698 | ulong2long(nlpd), |
| 1699 | rdtp->all_lazy ? 'L' : '.', |
| 1700 | rdtp->tick_nohz_enabled_snap ? '.' : 'D'); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1701 | } |
| 1702 | |
| 1703 | #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */ |
| 1704 | |
| 1705 | static void print_cpu_stall_fast_no_hz(char *cp, int cpu) |
| 1706 | { |
Carsten Emde | 1c17e4d | 2012-06-19 10:43:16 +0200 | [diff] [blame] | 1707 | *cp = '\0'; |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1708 | } |
| 1709 | |
| 1710 | #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */ |
| 1711 | |
| 1712 | /* Initiate the stall-info list. */ |
| 1713 | static void print_cpu_stall_info_begin(void) |
| 1714 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 1715 | pr_cont("\n"); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1716 | } |
| 1717 | |
| 1718 | /* |
| 1719 | * Print out diagnostic information for the specified stalled CPU. |
| 1720 | * |
| 1721 | * If the specified CPU is aware of the current RCU grace period |
| 1722 | * (flavor specified by rsp), then print the number of scheduling |
| 1723 | * clock interrupts the CPU has taken during the time that it has |
| 1724 | * been aware. Otherwise, print the number of RCU grace periods |
| 1725 | * that this CPU is ignorant of, for example, "1" if the CPU was |
| 1726 | * aware of the previous grace period. |
| 1727 | * |
| 1728 | * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info. |
| 1729 | */ |
| 1730 | static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) |
| 1731 | { |
| 1732 | char fast_no_hz[72]; |
| 1733 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
| 1734 | struct rcu_dynticks *rdtp = rdp->dynticks; |
| 1735 | char *ticks_title; |
| 1736 | unsigned long ticks_value; |
| 1737 | |
| 1738 | if (rsp->gpnum == rdp->gpnum) { |
| 1739 | ticks_title = "ticks this GP"; |
| 1740 | ticks_value = rdp->ticks_this_gp; |
| 1741 | } else { |
| 1742 | ticks_title = "GPs behind"; |
| 1743 | ticks_value = rsp->gpnum - rdp->gpnum; |
| 1744 | } |
| 1745 | print_cpu_stall_fast_no_hz(fast_no_hz, cpu); |
Paul E. McKenney | 7f21aee | 2015-08-15 14:49:50 -0700 | [diff] [blame] | 1746 | pr_err("\t%d-%c%c%c: (%lu %s) idle=%03x/%llx/%d softirq=%u/%u fqs=%ld %s\n", |
| 1747 | cpu, |
| 1748 | "O."[!!cpu_online(cpu)], |
| 1749 | "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)], |
| 1750 | "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)], |
| 1751 | ticks_value, ticks_title, |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1752 | atomic_read(&rdtp->dynticks) & 0xfff, |
| 1753 | rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting, |
Paul E. McKenney | 6231069 | 2013-03-06 13:37:09 -0800 | [diff] [blame] | 1754 | rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu), |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1755 | READ_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart, |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1756 | fast_no_hz); |
| 1757 | } |
| 1758 | |
| 1759 | /* Terminate the stall-info list. */ |
| 1760 | static void print_cpu_stall_info_end(void) |
| 1761 | { |
Paul E. McKenney | efc151c | 2013-03-18 16:24:11 -0700 | [diff] [blame] | 1762 | pr_err("\t"); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1763 | } |
| 1764 | |
| 1765 | /* Zero ->ticks_this_gp for all flavors of RCU. */ |
| 1766 | static void zero_cpu_stall_ticks(struct rcu_data *rdp) |
| 1767 | { |
| 1768 | rdp->ticks_this_gp = 0; |
Paul E. McKenney | 6231069 | 2013-03-06 13:37:09 -0800 | [diff] [blame] | 1769 | rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1770 | } |
| 1771 | |
| 1772 | /* Increment ->ticks_this_gp for all flavors of RCU. */ |
| 1773 | static void increment_cpu_stall_ticks(void) |
| 1774 | { |
Paul E. McKenney | 115f7a7 | 2012-08-10 13:55:03 -0700 | [diff] [blame] | 1775 | struct rcu_state *rsp; |
| 1776 | |
| 1777 | for_each_rcu_flavor(rsp) |
Christoph Lameter | fa07a58 | 2014-04-15 12:20:12 -0700 | [diff] [blame] | 1778 | raw_cpu_inc(rsp->rda->ticks_this_gp); |
Paul E. McKenney | a858af2 | 2012-01-16 13:29:10 -0800 | [diff] [blame] | 1779 | } |
| 1780 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1781 | #ifdef CONFIG_RCU_NOCB_CPU |
| 1782 | |
| 1783 | /* |
| 1784 | * Offload callback processing from the boot-time-specified set of CPUs |
| 1785 | * specified by rcu_nocb_mask. For each CPU in the set, there is a |
| 1786 | * kthread created that pulls the callbacks from the corresponding CPU, |
| 1787 | * waits for a grace period to elapse, and invokes the callbacks. |
| 1788 | * The no-CBs CPUs do a wake_up() on their kthread when they insert |
| 1789 | * a callback into any empty list, unless the rcu_nocb_poll boot parameter |
| 1790 | * has been specified, in which case each kthread actively polls its |
| 1791 | * CPU. (Which isn't so great for energy efficiency, but which does |
| 1792 | * reduce RCU's overhead on that CPU.) |
| 1793 | * |
| 1794 | * This is intended to be used in conjunction with Frederic Weisbecker's |
| 1795 | * adaptive-idle work, which would seriously reduce OS jitter on CPUs |
| 1796 | * running CPU-bound user-mode computations. |
| 1797 | * |
| 1798 | * Offloading of callback processing could also in theory be used as |
| 1799 | * an energy-efficiency measure because CPUs with no RCU callbacks |
| 1800 | * queued are more aggressive about entering dyntick-idle mode. |
| 1801 | */ |
| 1802 | |
| 1803 | |
| 1804 | /* Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters. */ |
| 1805 | static int __init rcu_nocb_setup(char *str) |
| 1806 | { |
| 1807 | alloc_bootmem_cpumask_var(&rcu_nocb_mask); |
| 1808 | have_rcu_nocb_mask = true; |
| 1809 | cpulist_parse(str, rcu_nocb_mask); |
| 1810 | return 1; |
| 1811 | } |
| 1812 | __setup("rcu_nocbs=", rcu_nocb_setup); |
| 1813 | |
Paul Gortmaker | 1b0048a | 2012-12-20 13:19:22 -0800 | [diff] [blame] | 1814 | static int __init parse_rcu_nocb_poll(char *arg) |
| 1815 | { |
| 1816 | rcu_nocb_poll = 1; |
| 1817 | return 0; |
| 1818 | } |
| 1819 | early_param("rcu_nocb_poll", parse_rcu_nocb_poll); |
| 1820 | |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 1821 | /* |
Paul E. McKenney | 0446be4 | 2012-12-30 15:21:01 -0800 | [diff] [blame] | 1822 | * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended |
| 1823 | * grace period. |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1824 | */ |
Paul E. McKenney | 0446be4 | 2012-12-30 15:21:01 -0800 | [diff] [blame] | 1825 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1826 | { |
Paul E. McKenney | 0446be4 | 2012-12-30 15:21:01 -0800 | [diff] [blame] | 1827 | wake_up_all(&rnp->nocb_gp_wq[rnp->completed & 0x1]); |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1828 | } |
| 1829 | |
| 1830 | /* |
Paul E. McKenney | 8b425aa8 | 2012-12-30 13:06:35 -0800 | [diff] [blame] | 1831 | * Set the root rcu_node structure's ->need_future_gp field |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1832 | * based on the sum of those of all rcu_node structures. This does |
| 1833 | * double-count the root rcu_node structure's requests, but this |
| 1834 | * is necessary to handle the possibility of a rcu_nocb_kthread() |
| 1835 | * having awakened during the time that the rcu_node structures |
| 1836 | * were being updated for the end of the previous grace period. |
| 1837 | */ |
| 1838 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
| 1839 | { |
Paul E. McKenney | 8b425aa8 | 2012-12-30 13:06:35 -0800 | [diff] [blame] | 1840 | rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 1841 | } |
| 1842 | |
| 1843 | static void rcu_init_one_nocb(struct rcu_node *rnp) |
| 1844 | { |
| 1845 | init_waitqueue_head(&rnp->nocb_gp_wq[0]); |
| 1846 | init_waitqueue_head(&rnp->nocb_gp_wq[1]); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 1847 | } |
| 1848 | |
Paul E. McKenney | 2f33b51 | 2013-11-17 18:25:48 -0800 | [diff] [blame] | 1849 | #ifndef CONFIG_RCU_NOCB_CPU_ALL |
Liu Ping Fan | 24342c9 | 2014-02-24 06:18:09 -0800 | [diff] [blame] | 1850 | /* Is the specified CPU a no-CBs CPU? */ |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 1851 | bool rcu_is_nocb_cpu(int cpu) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1852 | { |
| 1853 | if (have_rcu_nocb_mask) |
| 1854 | return cpumask_test_cpu(cpu, rcu_nocb_mask); |
| 1855 | return false; |
| 1856 | } |
Paul E. McKenney | 2f33b51 | 2013-11-17 18:25:48 -0800 | [diff] [blame] | 1857 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1858 | |
| 1859 | /* |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1860 | * Kick the leader kthread for this NOCB group. |
| 1861 | */ |
| 1862 | static void wake_nocb_leader(struct rcu_data *rdp, bool force) |
| 1863 | { |
| 1864 | struct rcu_data *rdp_leader = rdp->nocb_leader; |
| 1865 | |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1866 | if (!READ_ONCE(rdp_leader->nocb_kthread)) |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1867 | return; |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1868 | if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) { |
Paul E. McKenney | 39953df | 2014-08-12 10:47:48 -0700 | [diff] [blame] | 1869 | /* Prior smp_mb__after_atomic() orders against prior enqueue. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1870 | WRITE_ONCE(rdp_leader->nocb_leader_sleep, false); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1871 | wake_up(&rdp_leader->nocb_wq); |
| 1872 | } |
| 1873 | } |
| 1874 | |
| 1875 | /* |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1876 | * Does the specified CPU need an RCU callback for the specified flavor |
| 1877 | * of rcu_barrier()? |
| 1878 | */ |
| 1879 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) |
| 1880 | { |
| 1881 | struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1882 | unsigned long ret; |
| 1883 | #ifdef CONFIG_PROVE_RCU |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1884 | struct rcu_head *rhp; |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1885 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1886 | |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1887 | /* |
| 1888 | * Check count of all no-CBs callbacks awaiting invocation. |
| 1889 | * There needs to be a barrier before this function is called, |
| 1890 | * but associated with a prior determination that no more |
| 1891 | * callbacks would be posted. In the worst case, the first |
| 1892 | * barrier in _rcu_barrier() suffices (but the caller cannot |
| 1893 | * necessarily rely on this, not a substitute for the caller |
| 1894 | * getting the concurrency design right!). There must also be |
| 1895 | * a barrier between the following load an posting of a callback |
| 1896 | * (if a callback is in fact needed). This is associated with an |
| 1897 | * atomic_inc() in the caller. |
| 1898 | */ |
| 1899 | ret = atomic_long_read(&rdp->nocb_q_count); |
| 1900 | |
| 1901 | #ifdef CONFIG_PROVE_RCU |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1902 | rhp = READ_ONCE(rdp->nocb_head); |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1903 | if (!rhp) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1904 | rhp = READ_ONCE(rdp->nocb_gp_head); |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1905 | if (!rhp) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1906 | rhp = READ_ONCE(rdp->nocb_follower_head); |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1907 | |
| 1908 | /* Having no rcuo kthread but CBs after scheduler starts is bad! */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1909 | if (!READ_ONCE(rdp->nocb_kthread) && rhp && |
Paul E. McKenney | 59f792d | 2015-01-19 21:43:40 -0800 | [diff] [blame] | 1910 | rcu_scheduler_fully_active) { |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1911 | /* RCU callback enqueued before CPU first came online??? */ |
| 1912 | pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n", |
| 1913 | cpu, rhp->func); |
| 1914 | WARN_ON_ONCE(1); |
| 1915 | } |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1916 | #endif /* #ifdef CONFIG_PROVE_RCU */ |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1917 | |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1918 | return !!ret; |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 1919 | } |
| 1920 | |
| 1921 | /* |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1922 | * Enqueue the specified string of rcu_head structures onto the specified |
| 1923 | * CPU's no-CBs lists. The CPU is specified by rdp, the head of the |
| 1924 | * string by rhp, and the tail of the string by rhtp. The non-lazy/lazy |
| 1925 | * counts are supplied by rhcount and rhcount_lazy. |
| 1926 | * |
| 1927 | * If warranted, also wake up the kthread servicing this CPUs queues. |
| 1928 | */ |
| 1929 | static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, |
| 1930 | struct rcu_head *rhp, |
| 1931 | struct rcu_head **rhtp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1932 | int rhcount, int rhcount_lazy, |
| 1933 | unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1934 | { |
| 1935 | int len; |
| 1936 | struct rcu_head **old_rhpp; |
| 1937 | struct task_struct *t; |
| 1938 | |
| 1939 | /* Enqueue the callback on the nocb list and update counts. */ |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 1940 | atomic_long_add(rhcount, &rdp->nocb_q_count); |
| 1941 | /* rcu_barrier() relies on ->nocb_q_count add before xchg. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1942 | old_rhpp = xchg(&rdp->nocb_tail, rhtp); |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1943 | WRITE_ONCE(*old_rhpp, rhp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1944 | atomic_long_add(rhcount_lazy, &rdp->nocb_q_count_lazy); |
Paul E. McKenney | 39953df | 2014-08-12 10:47:48 -0700 | [diff] [blame] | 1945 | smp_mb__after_atomic(); /* Store *old_rhpp before _wake test. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1946 | |
| 1947 | /* If we are not being polled and there is a kthread, awaken it ... */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 1948 | t = READ_ONCE(rdp->nocb_kthread); |
Paul E. McKenney | 25e03a7 | 2013-10-15 12:47:04 -0700 | [diff] [blame] | 1949 | if (rcu_nocb_poll || !t) { |
Paul E. McKenney | 9261dd0 | 2013-08-14 16:24:26 -0700 | [diff] [blame] | 1950 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1951 | TPS("WakeNotPoll")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1952 | return; |
Paul E. McKenney | 9261dd0 | 2013-08-14 16:24:26 -0700 | [diff] [blame] | 1953 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1954 | len = atomic_long_read(&rdp->nocb_q_count); |
| 1955 | if (old_rhpp == &rdp->nocb_head) { |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1956 | if (!irqs_disabled_flags(flags)) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1957 | /* ... if queue was empty ... */ |
| 1958 | wake_nocb_leader(rdp, false); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1959 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1960 | TPS("WakeEmpty")); |
| 1961 | } else { |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 1962 | rdp->nocb_defer_wakeup = RCU_NOGP_WAKE; |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1963 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1964 | TPS("WakeEmptyIsDeferred")); |
| 1965 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1966 | rdp->qlen_last_fqs_check = 0; |
| 1967 | } else if (len > rdp->qlen_last_fqs_check + qhimark) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 1968 | /* ... or if many callbacks queued. */ |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 1969 | if (!irqs_disabled_flags(flags)) { |
| 1970 | wake_nocb_leader(rdp, true); |
| 1971 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1972 | TPS("WakeOvf")); |
| 1973 | } else { |
| 1974 | rdp->nocb_defer_wakeup = RCU_NOGP_WAKE_FORCE; |
| 1975 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 1976 | TPS("WakeOvfIsDeferred")); |
| 1977 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1978 | rdp->qlen_last_fqs_check = LONG_MAX / 2; |
Paul E. McKenney | 9261dd0 | 2013-08-14 16:24:26 -0700 | [diff] [blame] | 1979 | } else { |
| 1980 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1981 | } |
| 1982 | return; |
| 1983 | } |
| 1984 | |
| 1985 | /* |
| 1986 | * This is a helper for __call_rcu(), which invokes this when the normal |
| 1987 | * callback queue is inoperable. If this is not a no-CBs CPU, this |
| 1988 | * function returns failure back to __call_rcu(), which can complain |
| 1989 | * appropriately. |
| 1990 | * |
| 1991 | * Otherwise, this function queues the callback where the corresponding |
| 1992 | * "rcuo" kthread can find it. |
| 1993 | */ |
| 1994 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 1995 | bool lazy, unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 1996 | { |
| 1997 | |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 1998 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
Pranith Kumar | c271d3a | 2014-07-08 18:26:14 -0400 | [diff] [blame] | 1999 | return false; |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2000 | __call_rcu_nocb_enqueue(rdp, rhp, &rhp->next, 1, lazy, flags); |
Paul E. McKenney | 21e7a60 | 2013-02-09 17:42:16 -0800 | [diff] [blame] | 2001 | if (__is_kfree_rcu_offset((unsigned long)rhp->func)) |
| 2002 | trace_rcu_kfree_callback(rdp->rsp->name, rhp, |
| 2003 | (unsigned long)rhp->func, |
Paul E. McKenney | 756cbf6 | 2013-08-15 10:12:12 -0700 | [diff] [blame] | 2004 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
| 2005 | -atomic_long_read(&rdp->nocb_q_count)); |
Paul E. McKenney | 21e7a60 | 2013-02-09 17:42:16 -0800 | [diff] [blame] | 2006 | else |
| 2007 | trace_rcu_callback(rdp->rsp->name, rhp, |
Paul E. McKenney | 756cbf6 | 2013-08-15 10:12:12 -0700 | [diff] [blame] | 2008 | -atomic_long_read(&rdp->nocb_q_count_lazy), |
| 2009 | -atomic_long_read(&rdp->nocb_q_count)); |
Paul E. McKenney | 1772947bd | 2014-08-12 11:27:31 -0700 | [diff] [blame] | 2010 | |
| 2011 | /* |
| 2012 | * If called from an extended quiescent state with interrupts |
| 2013 | * disabled, invoke the RCU core in order to allow the idle-entry |
| 2014 | * deferred-wakeup check to function. |
| 2015 | */ |
| 2016 | if (irqs_disabled_flags(flags) && |
| 2017 | !rcu_is_watching() && |
| 2018 | cpu_online(smp_processor_id())) |
| 2019 | invoke_rcu_core(); |
| 2020 | |
Pranith Kumar | c271d3a | 2014-07-08 18:26:14 -0400 | [diff] [blame] | 2021 | return true; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2022 | } |
| 2023 | |
| 2024 | /* |
| 2025 | * Adopt orphaned callbacks on a no-CBs CPU, or return 0 if this is |
| 2026 | * not a no-CBs CPU. |
| 2027 | */ |
| 2028 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2029 | struct rcu_data *rdp, |
| 2030 | unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2031 | { |
| 2032 | long ql = rsp->qlen; |
| 2033 | long qll = rsp->qlen_lazy; |
| 2034 | |
| 2035 | /* If this is not a no-CBs CPU, tell the caller to do it the old way. */ |
Frederic Weisbecker | d1e43fa | 2013-03-26 23:47:24 +0100 | [diff] [blame] | 2036 | if (!rcu_is_nocb_cpu(smp_processor_id())) |
Pranith Kumar | 0a9e1e1 | 2014-07-08 18:26:15 -0400 | [diff] [blame] | 2037 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2038 | rsp->qlen = 0; |
| 2039 | rsp->qlen_lazy = 0; |
| 2040 | |
| 2041 | /* First, enqueue the donelist, if any. This preserves CB ordering. */ |
| 2042 | if (rsp->orphan_donelist != NULL) { |
| 2043 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_donelist, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2044 | rsp->orphan_donetail, ql, qll, flags); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2045 | ql = qll = 0; |
| 2046 | rsp->orphan_donelist = NULL; |
| 2047 | rsp->orphan_donetail = &rsp->orphan_donelist; |
| 2048 | } |
| 2049 | if (rsp->orphan_nxtlist != NULL) { |
| 2050 | __call_rcu_nocb_enqueue(rdp, rsp->orphan_nxtlist, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2051 | rsp->orphan_nxttail, ql, qll, flags); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2052 | ql = qll = 0; |
| 2053 | rsp->orphan_nxtlist = NULL; |
| 2054 | rsp->orphan_nxttail = &rsp->orphan_nxtlist; |
| 2055 | } |
Pranith Kumar | 0a9e1e1 | 2014-07-08 18:26:15 -0400 | [diff] [blame] | 2056 | return true; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2057 | } |
| 2058 | |
| 2059 | /* |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2060 | * If necessary, kick off a new grace period, and either way wait |
| 2061 | * for a subsequent grace period to complete. |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2062 | */ |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2063 | static void rcu_nocb_wait_gp(struct rcu_data *rdp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2064 | { |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2065 | unsigned long c; |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2066 | bool d; |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2067 | unsigned long flags; |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 2068 | bool needwake; |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2069 | struct rcu_node *rnp = rdp->mynode; |
| 2070 | |
| 2071 | raw_spin_lock_irqsave(&rnp->lock, flags); |
Paul E. McKenney | 6303b9c | 2013-12-11 13:59:10 -0800 | [diff] [blame] | 2072 | smp_mb__after_unlock_lock(); |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 2073 | needwake = rcu_start_future_gp(rnp, rdp, &c); |
Paul E. McKenney | 0446be4 | 2012-12-30 15:21:01 -0800 | [diff] [blame] | 2074 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
Paul E. McKenney | 48a7639 | 2014-03-11 13:02:16 -0700 | [diff] [blame] | 2075 | if (needwake) |
| 2076 | rcu_gp_kthread_wake(rdp->rsp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2077 | |
| 2078 | /* |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2079 | * Wait for the grace period. Do so interruptibly to avoid messing |
| 2080 | * up the load average. |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2081 | */ |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 2082 | trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2083 | for (;;) { |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2084 | wait_event_interruptible( |
| 2085 | rnp->nocb_gp_wq[c & 0x1], |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2086 | (d = ULONG_CMP_GE(READ_ONCE(rnp->completed), c))); |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2087 | if (likely(d)) |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2088 | break; |
Paul E. McKenney | 73a860c | 2014-08-14 10:28:23 -0700 | [diff] [blame] | 2089 | WARN_ON(signal_pending(current)); |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 2090 | trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2091 | } |
Steven Rostedt (Red Hat) | f7f7bac | 2013-07-12 17:18:47 -0400 | [diff] [blame] | 2092 | trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2093 | smp_mb(); /* Ensure that CB invocation happens after GP end. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2094 | } |
| 2095 | |
| 2096 | /* |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2097 | * Leaders come here to wait for additional callbacks to show up. |
| 2098 | * This function does not return until callbacks appear. |
| 2099 | */ |
| 2100 | static void nocb_leader_wait(struct rcu_data *my_rdp) |
| 2101 | { |
| 2102 | bool firsttime = true; |
| 2103 | bool gotcbs; |
| 2104 | struct rcu_data *rdp; |
| 2105 | struct rcu_head **tail; |
| 2106 | |
| 2107 | wait_again: |
| 2108 | |
| 2109 | /* Wait for callbacks to appear. */ |
| 2110 | if (!rcu_nocb_poll) { |
| 2111 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Sleep"); |
| 2112 | wait_event_interruptible(my_rdp->nocb_wq, |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2113 | !READ_ONCE(my_rdp->nocb_leader_sleep)); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2114 | /* Memory barrier handled by smp_mb() calls below and repoll. */ |
| 2115 | } else if (firsttime) { |
| 2116 | firsttime = false; /* Don't drown trace log with "Poll"! */ |
| 2117 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, "Poll"); |
| 2118 | } |
| 2119 | |
| 2120 | /* |
| 2121 | * Each pass through the following loop checks a follower for CBs. |
| 2122 | * We are our own first follower. Any CBs found are moved to |
| 2123 | * nocb_gp_head, where they await a grace period. |
| 2124 | */ |
| 2125 | gotcbs = false; |
| 2126 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2127 | rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2128 | if (!rdp->nocb_gp_head) |
| 2129 | continue; /* No CBs here, try next follower. */ |
| 2130 | |
| 2131 | /* Move callbacks to wait-for-GP list, which is empty. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2132 | WRITE_ONCE(rdp->nocb_head, NULL); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2133 | rdp->nocb_gp_tail = xchg(&rdp->nocb_tail, &rdp->nocb_head); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2134 | gotcbs = true; |
| 2135 | } |
| 2136 | |
| 2137 | /* |
| 2138 | * If there were no callbacks, sleep a bit, rescan after a |
| 2139 | * memory barrier, and go retry. |
| 2140 | */ |
| 2141 | if (unlikely(!gotcbs)) { |
| 2142 | if (!rcu_nocb_poll) |
| 2143 | trace_rcu_nocb_wake(my_rdp->rsp->name, my_rdp->cpu, |
| 2144 | "WokeEmpty"); |
Paul E. McKenney | 73a860c | 2014-08-14 10:28:23 -0700 | [diff] [blame] | 2145 | WARN_ON(signal_pending(current)); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2146 | schedule_timeout_interruptible(1); |
| 2147 | |
| 2148 | /* Rescan in case we were a victim of memory ordering. */ |
Pranith Kumar | 11ed7f9 | 2014-08-27 16:43:40 -0400 | [diff] [blame] | 2149 | my_rdp->nocb_leader_sleep = true; |
| 2150 | smp_mb(); /* Ensure _sleep true before scan. */ |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2151 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2152 | if (READ_ONCE(rdp->nocb_head)) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2153 | /* Found CB, so short-circuit next wait. */ |
Pranith Kumar | 11ed7f9 | 2014-08-27 16:43:40 -0400 | [diff] [blame] | 2154 | my_rdp->nocb_leader_sleep = false; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2155 | break; |
| 2156 | } |
| 2157 | goto wait_again; |
| 2158 | } |
| 2159 | |
| 2160 | /* Wait for one grace period. */ |
| 2161 | rcu_nocb_wait_gp(my_rdp); |
| 2162 | |
| 2163 | /* |
Pranith Kumar | 11ed7f9 | 2014-08-27 16:43:40 -0400 | [diff] [blame] | 2164 | * We left ->nocb_leader_sleep unset to reduce cache thrashing. |
| 2165 | * We set it now, but recheck for new callbacks while |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2166 | * traversing our follower list. |
| 2167 | */ |
Pranith Kumar | 11ed7f9 | 2014-08-27 16:43:40 -0400 | [diff] [blame] | 2168 | my_rdp->nocb_leader_sleep = true; |
| 2169 | smp_mb(); /* Ensure _sleep true before scan of ->nocb_head. */ |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2170 | |
| 2171 | /* Each pass through the following loop wakes a follower, if needed. */ |
| 2172 | for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2173 | if (READ_ONCE(rdp->nocb_head)) |
Pranith Kumar | 11ed7f9 | 2014-08-27 16:43:40 -0400 | [diff] [blame] | 2174 | my_rdp->nocb_leader_sleep = false;/* No need to sleep.*/ |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2175 | if (!rdp->nocb_gp_head) |
| 2176 | continue; /* No CBs, so no need to wake follower. */ |
| 2177 | |
| 2178 | /* Append callbacks to follower's "done" list. */ |
| 2179 | tail = xchg(&rdp->nocb_follower_tail, rdp->nocb_gp_tail); |
| 2180 | *tail = rdp->nocb_gp_head; |
Paul E. McKenney | c847f14 | 2014-08-12 13:54:21 -0700 | [diff] [blame] | 2181 | smp_mb__after_atomic(); /* Store *tail before wakeup. */ |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2182 | if (rdp != my_rdp && tail == &rdp->nocb_follower_head) { |
| 2183 | /* |
| 2184 | * List was empty, wake up the follower. |
| 2185 | * Memory barriers supplied by atomic_long_add(). |
| 2186 | */ |
| 2187 | wake_up(&rdp->nocb_wq); |
| 2188 | } |
| 2189 | } |
| 2190 | |
| 2191 | /* If we (the leader) don't have CBs, go wait some more. */ |
| 2192 | if (!my_rdp->nocb_follower_head) |
| 2193 | goto wait_again; |
| 2194 | } |
| 2195 | |
| 2196 | /* |
| 2197 | * Followers come here to wait for additional callbacks to show up. |
| 2198 | * This function does not return until callbacks appear. |
| 2199 | */ |
| 2200 | static void nocb_follower_wait(struct rcu_data *rdp) |
| 2201 | { |
| 2202 | bool firsttime = true; |
| 2203 | |
| 2204 | for (;;) { |
| 2205 | if (!rcu_nocb_poll) { |
| 2206 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 2207 | "FollowerSleep"); |
| 2208 | wait_event_interruptible(rdp->nocb_wq, |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2209 | READ_ONCE(rdp->nocb_follower_head)); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2210 | } else if (firsttime) { |
| 2211 | /* Don't drown trace log with "Poll"! */ |
| 2212 | firsttime = false; |
| 2213 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "Poll"); |
| 2214 | } |
| 2215 | if (smp_load_acquire(&rdp->nocb_follower_head)) { |
| 2216 | /* ^^^ Ensure CB invocation follows _head test. */ |
| 2217 | return; |
| 2218 | } |
| 2219 | if (!rcu_nocb_poll) |
| 2220 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 2221 | "WokeEmpty"); |
Paul E. McKenney | 73a860c | 2014-08-14 10:28:23 -0700 | [diff] [blame] | 2222 | WARN_ON(signal_pending(current)); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2223 | schedule_timeout_interruptible(1); |
| 2224 | } |
| 2225 | } |
| 2226 | |
| 2227 | /* |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2228 | * Per-rcu_data kthread, but only for no-CBs CPUs. Each kthread invokes |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2229 | * callbacks queued by the corresponding no-CBs CPU, however, there is |
| 2230 | * an optional leader-follower relationship so that the grace-period |
| 2231 | * kthreads don't have to do quite so many wakeups. |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2232 | */ |
| 2233 | static int rcu_nocb_kthread(void *arg) |
| 2234 | { |
| 2235 | int c, cl; |
| 2236 | struct rcu_head *list; |
| 2237 | struct rcu_head *next; |
| 2238 | struct rcu_head **tail; |
| 2239 | struct rcu_data *rdp = arg; |
| 2240 | |
| 2241 | /* Each pass through this loop invokes one batch of callbacks */ |
| 2242 | for (;;) { |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2243 | /* Wait for callbacks. */ |
| 2244 | if (rdp->nocb_leader == rdp) |
| 2245 | nocb_leader_wait(rdp); |
| 2246 | else |
| 2247 | nocb_follower_wait(rdp); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2248 | |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2249 | /* Pull the ready-to-invoke callbacks onto local list. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2250 | list = READ_ONCE(rdp->nocb_follower_head); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2251 | BUG_ON(!list); |
| 2252 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, "WokeNonEmpty"); |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2253 | WRITE_ONCE(rdp->nocb_follower_head, NULL); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2254 | tail = xchg(&rdp->nocb_follower_tail, &rdp->nocb_follower_head); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2255 | |
| 2256 | /* Each pass through the following loop invokes a callback. */ |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 2257 | trace_rcu_batch_start(rdp->rsp->name, |
| 2258 | atomic_long_read(&rdp->nocb_q_count_lazy), |
| 2259 | atomic_long_read(&rdp->nocb_q_count), -1); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2260 | c = cl = 0; |
| 2261 | while (list) { |
| 2262 | next = list->next; |
| 2263 | /* Wait for enqueuing to complete, if needed. */ |
| 2264 | while (next == NULL && &list->next != tail) { |
Paul E. McKenney | 69a79bb | 2013-08-15 13:23:23 -0700 | [diff] [blame] | 2265 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 2266 | TPS("WaitQueue")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2267 | schedule_timeout_interruptible(1); |
Paul E. McKenney | 69a79bb | 2013-08-15 13:23:23 -0700 | [diff] [blame] | 2268 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, |
| 2269 | TPS("WokeQueue")); |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2270 | next = list->next; |
| 2271 | } |
| 2272 | debug_rcu_head_unqueue(list); |
| 2273 | local_bh_disable(); |
| 2274 | if (__rcu_reclaim(rdp->rsp->name, list)) |
| 2275 | cl++; |
| 2276 | c++; |
| 2277 | local_bh_enable(); |
| 2278 | list = next; |
| 2279 | } |
| 2280 | trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); |
Paul E. McKenney | 41050a0 | 2014-12-18 12:31:27 -0800 | [diff] [blame] | 2281 | smp_mb__before_atomic(); /* _add after CB invocation. */ |
| 2282 | atomic_long_add(-c, &rdp->nocb_q_count); |
| 2283 | atomic_long_add(-cl, &rdp->nocb_q_count_lazy); |
Paul E. McKenney | c635a4e1 | 2012-10-29 07:29:20 -0700 | [diff] [blame] | 2284 | rdp->n_nocbs_invoked += c; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2285 | } |
| 2286 | return 0; |
| 2287 | } |
| 2288 | |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2289 | /* Is a deferred wakeup of rcu_nocb_kthread() required? */ |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2290 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2291 | { |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2292 | return READ_ONCE(rdp->nocb_defer_wakeup); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2293 | } |
| 2294 | |
| 2295 | /* Do a deferred wakeup of rcu_nocb_kthread(). */ |
| 2296 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) |
| 2297 | { |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2298 | int ndw; |
| 2299 | |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2300 | if (!rcu_nocb_need_deferred_wakeup(rdp)) |
| 2301 | return; |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2302 | ndw = READ_ONCE(rdp->nocb_defer_wakeup); |
| 2303 | WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOGP_WAKE_NOT); |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2304 | wake_nocb_leader(rdp, ndw == RCU_NOGP_WAKE_FORCE); |
| 2305 | trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2306 | } |
| 2307 | |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2308 | void __init rcu_init_nohz(void) |
| 2309 | { |
| 2310 | int cpu; |
| 2311 | bool need_rcu_nocb_mask = true; |
| 2312 | struct rcu_state *rsp; |
| 2313 | |
| 2314 | #ifdef CONFIG_RCU_NOCB_CPU_NONE |
| 2315 | need_rcu_nocb_mask = false; |
| 2316 | #endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ |
| 2317 | |
| 2318 | #if defined(CONFIG_NO_HZ_FULL) |
| 2319 | if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) |
| 2320 | need_rcu_nocb_mask = true; |
| 2321 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ |
| 2322 | |
| 2323 | if (!have_rcu_nocb_mask && need_rcu_nocb_mask) { |
Pranith Kumar | 949cccd | 2014-07-25 16:02:07 -0700 | [diff] [blame] | 2324 | if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { |
| 2325 | pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); |
| 2326 | return; |
| 2327 | } |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2328 | have_rcu_nocb_mask = true; |
| 2329 | } |
| 2330 | if (!have_rcu_nocb_mask) |
| 2331 | return; |
| 2332 | |
| 2333 | #ifdef CONFIG_RCU_NOCB_CPU_ZERO |
| 2334 | pr_info("\tOffload RCU callbacks from CPU 0\n"); |
| 2335 | cpumask_set_cpu(0, rcu_nocb_mask); |
| 2336 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ |
| 2337 | #ifdef CONFIG_RCU_NOCB_CPU_ALL |
| 2338 | pr_info("\tOffload RCU callbacks from all CPUs\n"); |
| 2339 | cpumask_copy(rcu_nocb_mask, cpu_possible_mask); |
| 2340 | #endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ |
| 2341 | #if defined(CONFIG_NO_HZ_FULL) |
| 2342 | if (tick_nohz_full_running) |
| 2343 | cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); |
| 2344 | #endif /* #if defined(CONFIG_NO_HZ_FULL) */ |
| 2345 | |
| 2346 | if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { |
| 2347 | pr_info("\tNote: kernel parameter 'rcu_nocbs=' contains nonexistent CPUs.\n"); |
| 2348 | cpumask_and(rcu_nocb_mask, cpu_possible_mask, |
| 2349 | rcu_nocb_mask); |
| 2350 | } |
Tejun Heo | ad853b4 | 2015-02-13 14:37:25 -0800 | [diff] [blame] | 2351 | pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n", |
| 2352 | cpumask_pr_args(rcu_nocb_mask)); |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2353 | if (rcu_nocb_poll) |
| 2354 | pr_info("\tPoll for callbacks from no-CBs CPUs.\n"); |
| 2355 | |
| 2356 | for_each_rcu_flavor(rsp) { |
Paul E. McKenney | 34404ca | 2015-01-19 20:39:20 -0800 | [diff] [blame] | 2357 | for_each_cpu(cpu, rcu_nocb_mask) |
| 2358 | init_nocb_callback_list(per_cpu_ptr(rsp->rda, cpu)); |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2359 | rcu_organize_nocb_kthreads(rsp); |
Paul E. McKenney | f4579fc | 2014-07-25 11:21:47 -0700 | [diff] [blame] | 2360 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2361 | } |
| 2362 | |
| 2363 | /* Initialize per-rcu_data variables for no-CBs CPUs. */ |
| 2364 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
| 2365 | { |
| 2366 | rdp->nocb_tail = &rdp->nocb_head; |
| 2367 | init_waitqueue_head(&rdp->nocb_wq); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2368 | rdp->nocb_follower_tail = &rdp->nocb_follower_head; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2369 | } |
| 2370 | |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2371 | /* |
| 2372 | * If the specified CPU is a no-CBs CPU that does not already have its |
| 2373 | * rcuo kthread for the specified RCU flavor, spawn it. If the CPUs are |
| 2374 | * brought online out of order, this can require re-organizing the |
| 2375 | * leader-follower relationships. |
| 2376 | */ |
| 2377 | static void rcu_spawn_one_nocb_kthread(struct rcu_state *rsp, int cpu) |
| 2378 | { |
| 2379 | struct rcu_data *rdp; |
| 2380 | struct rcu_data *rdp_last; |
| 2381 | struct rcu_data *rdp_old_leader; |
| 2382 | struct rcu_data *rdp_spawn = per_cpu_ptr(rsp->rda, cpu); |
| 2383 | struct task_struct *t; |
| 2384 | |
| 2385 | /* |
| 2386 | * If this isn't a no-CBs CPU or if it already has an rcuo kthread, |
| 2387 | * then nothing to do. |
| 2388 | */ |
| 2389 | if (!rcu_is_nocb_cpu(cpu) || rdp_spawn->nocb_kthread) |
| 2390 | return; |
| 2391 | |
| 2392 | /* If we didn't spawn the leader first, reorganize! */ |
| 2393 | rdp_old_leader = rdp_spawn->nocb_leader; |
| 2394 | if (rdp_old_leader != rdp_spawn && !rdp_old_leader->nocb_kthread) { |
| 2395 | rdp_last = NULL; |
| 2396 | rdp = rdp_old_leader; |
| 2397 | do { |
| 2398 | rdp->nocb_leader = rdp_spawn; |
| 2399 | if (rdp_last && rdp != rdp_spawn) |
| 2400 | rdp_last->nocb_next_follower = rdp; |
Paul E. McKenney | bbe5d7a | 2014-10-24 11:11:08 -0700 | [diff] [blame] | 2401 | if (rdp == rdp_spawn) { |
| 2402 | rdp = rdp->nocb_next_follower; |
| 2403 | } else { |
| 2404 | rdp_last = rdp; |
| 2405 | rdp = rdp->nocb_next_follower; |
| 2406 | rdp_last->nocb_next_follower = NULL; |
| 2407 | } |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2408 | } while (rdp); |
| 2409 | rdp_spawn->nocb_next_follower = rdp_old_leader; |
| 2410 | } |
| 2411 | |
| 2412 | /* Spawn the kthread for this CPU and RCU flavor. */ |
| 2413 | t = kthread_run(rcu_nocb_kthread, rdp_spawn, |
| 2414 | "rcuo%c/%d", rsp->abbr, cpu); |
| 2415 | BUG_ON(IS_ERR(t)); |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2416 | WRITE_ONCE(rdp_spawn->nocb_kthread, t); |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2417 | } |
| 2418 | |
| 2419 | /* |
| 2420 | * If the specified CPU is a no-CBs CPU that does not already have its |
| 2421 | * rcuo kthreads, spawn them. |
| 2422 | */ |
| 2423 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
| 2424 | { |
| 2425 | struct rcu_state *rsp; |
| 2426 | |
| 2427 | if (rcu_scheduler_fully_active) |
| 2428 | for_each_rcu_flavor(rsp) |
| 2429 | rcu_spawn_one_nocb_kthread(rsp, cpu); |
| 2430 | } |
| 2431 | |
| 2432 | /* |
| 2433 | * Once the scheduler is running, spawn rcuo kthreads for all online |
| 2434 | * no-CBs CPUs. This assumes that the early_initcall()s happen before |
| 2435 | * non-boot CPUs come online -- if this changes, we will need to add |
| 2436 | * some mutual exclusion. |
| 2437 | */ |
| 2438 | static void __init rcu_spawn_nocb_kthreads(void) |
| 2439 | { |
| 2440 | int cpu; |
| 2441 | |
| 2442 | for_each_online_cpu(cpu) |
| 2443 | rcu_spawn_all_nocb_kthreads(cpu); |
| 2444 | } |
| 2445 | |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2446 | /* How many follower CPU IDs per leader? Default of -1 for sqrt(nr_cpu_ids). */ |
| 2447 | static int rcu_nocb_leader_stride = -1; |
| 2448 | module_param(rcu_nocb_leader_stride, int, 0444); |
| 2449 | |
| 2450 | /* |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2451 | * Initialize leader-follower relationships for all no-CBs CPU. |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2452 | */ |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2453 | static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2454 | { |
| 2455 | int cpu; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2456 | int ls = rcu_nocb_leader_stride; |
| 2457 | int nl = 0; /* Next leader. */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2458 | struct rcu_data *rdp; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2459 | struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ |
| 2460 | struct rcu_data *rdp_prev = NULL; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2461 | |
Pranith Kumar | 22c2f66 | 2014-07-17 20:11:01 -0400 | [diff] [blame] | 2462 | if (!have_rcu_nocb_mask) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2463 | return; |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2464 | if (ls == -1) { |
| 2465 | ls = int_sqrt(nr_cpu_ids); |
| 2466 | rcu_nocb_leader_stride = ls; |
| 2467 | } |
| 2468 | |
| 2469 | /* |
| 2470 | * Each pass through this loop sets up one rcu_data structure and |
| 2471 | * spawns one rcu_nocb_kthread(). |
| 2472 | */ |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2473 | for_each_cpu(cpu, rcu_nocb_mask) { |
| 2474 | rdp = per_cpu_ptr(rsp->rda, cpu); |
Paul E. McKenney | fbce749 | 2014-06-24 09:26:11 -0700 | [diff] [blame] | 2475 | if (rdp->cpu >= nl) { |
| 2476 | /* New leader, set up for followers & next leader. */ |
| 2477 | nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls; |
| 2478 | rdp->nocb_leader = rdp; |
| 2479 | rdp_leader = rdp; |
| 2480 | } else { |
| 2481 | /* Another follower, link to previous leader. */ |
| 2482 | rdp->nocb_leader = rdp_leader; |
| 2483 | rdp_prev->nocb_next_follower = rdp; |
| 2484 | } |
| 2485 | rdp_prev = rdp; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2486 | } |
| 2487 | } |
| 2488 | |
| 2489 | /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2490 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2491 | { |
Pranith Kumar | 22c2f66 | 2014-07-17 20:11:01 -0400 | [diff] [blame] | 2492 | if (!rcu_is_nocb_cpu(rdp->cpu)) |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2493 | return false; |
Pranith Kumar | 22c2f66 | 2014-07-17 20:11:01 -0400 | [diff] [blame] | 2494 | |
Paul E. McKenney | 34404ca | 2015-01-19 20:39:20 -0800 | [diff] [blame] | 2495 | /* If there are early-boot callbacks, move them to nocb lists. */ |
| 2496 | if (rdp->nxtlist) { |
| 2497 | rdp->nocb_head = rdp->nxtlist; |
| 2498 | rdp->nocb_tail = rdp->nxttail[RCU_NEXT_TAIL]; |
| 2499 | atomic_long_set(&rdp->nocb_q_count, rdp->qlen); |
| 2500 | atomic_long_set(&rdp->nocb_q_count_lazy, rdp->qlen_lazy); |
| 2501 | rdp->nxtlist = NULL; |
| 2502 | rdp->qlen = 0; |
| 2503 | rdp->qlen_lazy = 0; |
| 2504 | } |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2505 | rdp->nxttail[RCU_NEXT_TAIL] = NULL; |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2506 | return true; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2507 | } |
| 2508 | |
| 2509 | #else /* #ifdef CONFIG_RCU_NOCB_CPU */ |
| 2510 | |
Paul E. McKenney | d7e2993 | 2014-10-27 09:15:54 -0700 | [diff] [blame] | 2511 | static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu) |
| 2512 | { |
| 2513 | WARN_ON_ONCE(1); /* Should be dead code. */ |
| 2514 | return false; |
| 2515 | } |
| 2516 | |
Paul E. McKenney | 0446be4 | 2012-12-30 15:21:01 -0800 | [diff] [blame] | 2517 | static void rcu_nocb_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2518 | { |
Paul E. McKenney | dae6e64 | 2013-02-10 20:48:58 -0800 | [diff] [blame] | 2519 | } |
| 2520 | |
| 2521 | static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) |
| 2522 | { |
| 2523 | } |
| 2524 | |
| 2525 | static void rcu_init_one_nocb(struct rcu_node *rnp) |
| 2526 | { |
| 2527 | } |
| 2528 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2529 | static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2530 | bool lazy, unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2531 | { |
Pranith Kumar | 4afc7e2 | 2014-07-08 18:26:16 -0400 | [diff] [blame] | 2532 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2533 | } |
| 2534 | |
| 2535 | static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2536 | struct rcu_data *rdp, |
| 2537 | unsigned long flags) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2538 | { |
Pranith Kumar | f4aa84b | 2014-07-08 18:26:17 -0400 | [diff] [blame] | 2539 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2540 | } |
| 2541 | |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2542 | static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp) |
| 2543 | { |
| 2544 | } |
| 2545 | |
Paul E. McKenney | 9fdd3bc | 2014-07-29 14:50:47 -0700 | [diff] [blame] | 2546 | static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp) |
Paul E. McKenney | 96d3fd0 | 2013-10-04 14:33:34 -0700 | [diff] [blame] | 2547 | { |
| 2548 | return false; |
| 2549 | } |
| 2550 | |
| 2551 | static void do_nocb_deferred_wakeup(struct rcu_data *rdp) |
| 2552 | { |
| 2553 | } |
| 2554 | |
Paul E. McKenney | 35ce7f2 | 2014-07-11 11:30:24 -0700 | [diff] [blame] | 2555 | static void rcu_spawn_all_nocb_kthreads(int cpu) |
| 2556 | { |
| 2557 | } |
| 2558 | |
| 2559 | static void __init rcu_spawn_nocb_kthreads(void) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2560 | { |
| 2561 | } |
| 2562 | |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2563 | static bool init_nocb_callback_list(struct rcu_data *rdp) |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2564 | { |
Paul E. McKenney | 34ed6246 | 2013-01-07 13:37:42 -0800 | [diff] [blame] | 2565 | return false; |
Paul E. McKenney | 3fbfbf7 | 2012-08-19 21:35:53 -0700 | [diff] [blame] | 2566 | } |
| 2567 | |
| 2568 | #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ |
Paul E. McKenney | 65d798f | 2013-04-12 16:19:10 -0700 | [diff] [blame] | 2569 | |
| 2570 | /* |
| 2571 | * An adaptive-ticks CPU can potentially execute in kernel mode for an |
| 2572 | * arbitrarily long period of time with the scheduling-clock tick turned |
| 2573 | * off. RCU will be paying attention to this CPU because it is in the |
| 2574 | * kernel, but the CPU cannot be guaranteed to be executing the RCU state |
| 2575 | * machine because the scheduling-clock tick has been disabled. Therefore, |
| 2576 | * if an adaptive-ticks CPU is failing to respond to the current grace |
| 2577 | * period and has not be idle from an RCU perspective, kick it. |
| 2578 | */ |
Paul E. McKenney | 4a81e83 | 2014-06-20 16:49:01 -0700 | [diff] [blame] | 2579 | static void __maybe_unused rcu_kick_nohz_cpu(int cpu) |
Paul E. McKenney | 65d798f | 2013-04-12 16:19:10 -0700 | [diff] [blame] | 2580 | { |
| 2581 | #ifdef CONFIG_NO_HZ_FULL |
| 2582 | if (tick_nohz_full_cpu(cpu)) |
| 2583 | smp_send_reschedule(cpu); |
| 2584 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ |
| 2585 | } |
Paul E. McKenney | 2333210 | 2013-06-21 12:34:33 -0700 | [diff] [blame] | 2586 | |
| 2587 | |
| 2588 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
| 2589 | |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2590 | static int full_sysidle_state; /* Current system-idle state. */ |
Paul E. McKenney | d4bd54f | 2013-06-21 14:51:40 -0700 | [diff] [blame] | 2591 | #define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ |
| 2592 | #define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ |
| 2593 | #define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ |
| 2594 | #define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ |
| 2595 | #define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ |
| 2596 | |
| 2597 | /* |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2598 | * Invoked to note exit from irq or task transition to idle. Note that |
| 2599 | * usermode execution does -not- count as idle here! After all, we want |
| 2600 | * to detect full-system idle states, not RCU quiescent states and grace |
| 2601 | * periods. The caller must have disabled interrupts. |
| 2602 | */ |
Christoph Lameter | 28ced79 | 2014-09-02 14:13:44 -0700 | [diff] [blame] | 2603 | static void rcu_sysidle_enter(int irq) |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2604 | { |
| 2605 | unsigned long j; |
Christoph Lameter | 28ced79 | 2014-09-02 14:13:44 -0700 | [diff] [blame] | 2606 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2607 | |
Paul E. McKenney | 663e131 | 2014-07-21 11:34:33 -0700 | [diff] [blame] | 2608 | /* If there are no nohz_full= CPUs, no need to track this. */ |
| 2609 | if (!tick_nohz_full_enabled()) |
| 2610 | return; |
| 2611 | |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2612 | /* Adjust nesting, check for fully idle. */ |
| 2613 | if (irq) { |
| 2614 | rdtp->dynticks_idle_nesting--; |
| 2615 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); |
| 2616 | if (rdtp->dynticks_idle_nesting != 0) |
| 2617 | return; /* Still not fully idle. */ |
| 2618 | } else { |
| 2619 | if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == |
| 2620 | DYNTICK_TASK_NEST_VALUE) { |
| 2621 | rdtp->dynticks_idle_nesting = 0; |
| 2622 | } else { |
| 2623 | rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; |
| 2624 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); |
| 2625 | return; /* Still not fully idle. */ |
| 2626 | } |
| 2627 | } |
| 2628 | |
| 2629 | /* Record start of fully idle period. */ |
| 2630 | j = jiffies; |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2631 | WRITE_ONCE(rdtp->dynticks_idle_jiffies, j); |
Peter Zijlstra | 4e857c5 | 2014-03-17 18:06:10 +0100 | [diff] [blame] | 2632 | smp_mb__before_atomic(); |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2633 | atomic_inc(&rdtp->dynticks_idle); |
Peter Zijlstra | 4e857c5 | 2014-03-17 18:06:10 +0100 | [diff] [blame] | 2634 | smp_mb__after_atomic(); |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2635 | WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); |
| 2636 | } |
| 2637 | |
| 2638 | /* |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2639 | * Unconditionally force exit from full system-idle state. This is |
| 2640 | * invoked when a normal CPU exits idle, but must be called separately |
| 2641 | * for the timekeeping CPU (tick_do_timer_cpu). The reason for this |
| 2642 | * is that the timekeeping CPU is permitted to take scheduling-clock |
| 2643 | * interrupts while the system is in system-idle state, and of course |
| 2644 | * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock |
| 2645 | * interrupt from any other type of interrupt. |
| 2646 | */ |
| 2647 | void rcu_sysidle_force_exit(void) |
| 2648 | { |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2649 | int oldstate = READ_ONCE(full_sysidle_state); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2650 | int newoldstate; |
| 2651 | |
| 2652 | /* |
| 2653 | * Each pass through the following loop attempts to exit full |
| 2654 | * system-idle state. If contention proves to be a problem, |
| 2655 | * a trylock-based contention tree could be used here. |
| 2656 | */ |
| 2657 | while (oldstate > RCU_SYSIDLE_SHORT) { |
| 2658 | newoldstate = cmpxchg(&full_sysidle_state, |
| 2659 | oldstate, RCU_SYSIDLE_NOT); |
| 2660 | if (oldstate == newoldstate && |
| 2661 | oldstate == RCU_SYSIDLE_FULL_NOTED) { |
| 2662 | rcu_kick_nohz_cpu(tick_do_timer_cpu); |
| 2663 | return; /* We cleared it, done! */ |
| 2664 | } |
| 2665 | oldstate = newoldstate; |
| 2666 | } |
| 2667 | smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ |
| 2668 | } |
| 2669 | |
| 2670 | /* |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2671 | * Invoked to note entry to irq or task transition from idle. Note that |
| 2672 | * usermode execution does -not- count as idle here! The caller must |
| 2673 | * have disabled interrupts. |
| 2674 | */ |
Christoph Lameter | 28ced79 | 2014-09-02 14:13:44 -0700 | [diff] [blame] | 2675 | static void rcu_sysidle_exit(int irq) |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2676 | { |
Christoph Lameter | 28ced79 | 2014-09-02 14:13:44 -0700 | [diff] [blame] | 2677 | struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); |
| 2678 | |
Paul E. McKenney | 663e131 | 2014-07-21 11:34:33 -0700 | [diff] [blame] | 2679 | /* If there are no nohz_full= CPUs, no need to track this. */ |
| 2680 | if (!tick_nohz_full_enabled()) |
| 2681 | return; |
| 2682 | |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2683 | /* Adjust nesting, check for already non-idle. */ |
| 2684 | if (irq) { |
| 2685 | rdtp->dynticks_idle_nesting++; |
| 2686 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); |
| 2687 | if (rdtp->dynticks_idle_nesting != 1) |
| 2688 | return; /* Already non-idle. */ |
| 2689 | } else { |
| 2690 | /* |
| 2691 | * Allow for irq misnesting. Yes, it really is possible |
| 2692 | * to enter an irq handler then never leave it, and maybe |
| 2693 | * also vice versa. Handle both possibilities. |
| 2694 | */ |
| 2695 | if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { |
| 2696 | rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; |
| 2697 | WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); |
| 2698 | return; /* Already non-idle. */ |
| 2699 | } else { |
| 2700 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; |
| 2701 | } |
| 2702 | } |
| 2703 | |
| 2704 | /* Record end of idle period. */ |
Peter Zijlstra | 4e857c5 | 2014-03-17 18:06:10 +0100 | [diff] [blame] | 2705 | smp_mb__before_atomic(); |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2706 | atomic_inc(&rdtp->dynticks_idle); |
Peter Zijlstra | 4e857c5 | 2014-03-17 18:06:10 +0100 | [diff] [blame] | 2707 | smp_mb__after_atomic(); |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2708 | WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2709 | |
| 2710 | /* |
| 2711 | * If we are the timekeeping CPU, we are permitted to be non-idle |
| 2712 | * during a system-idle state. This must be the case, because |
| 2713 | * the timekeeping CPU has to take scheduling-clock interrupts |
| 2714 | * during the time that the system is transitioning to full |
| 2715 | * system-idle state. This means that the timekeeping CPU must |
| 2716 | * invoke rcu_sysidle_force_exit() directly if it does anything |
| 2717 | * more than take a scheduling-clock interrupt. |
| 2718 | */ |
| 2719 | if (smp_processor_id() == tick_do_timer_cpu) |
| 2720 | return; |
| 2721 | |
| 2722 | /* Update system-idle state: We are clearly no longer fully idle! */ |
| 2723 | rcu_sysidle_force_exit(); |
| 2724 | } |
| 2725 | |
| 2726 | /* |
| 2727 | * Check to see if the current CPU is idle. Note that usermode execution |
Paul E. McKenney | 5871968 | 2015-02-24 11:05:36 -0800 | [diff] [blame] | 2728 | * does not count as idle. The caller must have disabled interrupts, |
| 2729 | * and must be running on tick_do_timer_cpu. |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2730 | */ |
| 2731 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, |
| 2732 | unsigned long *maxj) |
| 2733 | { |
| 2734 | int cur; |
| 2735 | unsigned long j; |
| 2736 | struct rcu_dynticks *rdtp = rdp->dynticks; |
| 2737 | |
Paul E. McKenney | 663e131 | 2014-07-21 11:34:33 -0700 | [diff] [blame] | 2738 | /* If there are no nohz_full= CPUs, don't check system-wide idleness. */ |
| 2739 | if (!tick_nohz_full_enabled()) |
| 2740 | return; |
| 2741 | |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2742 | /* |
| 2743 | * If some other CPU has already reported non-idle, if this is |
| 2744 | * not the flavor of RCU that tracks sysidle state, or if this |
| 2745 | * is an offline or the timekeeping CPU, nothing to do. |
| 2746 | */ |
Paul E. McKenney | 417e8d2 | 2014-07-21 11:26:54 -0700 | [diff] [blame] | 2747 | if (!*isidle || rdp->rsp != rcu_state_p || |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2748 | cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) |
| 2749 | return; |
Paul E. McKenney | 5871968 | 2015-02-24 11:05:36 -0800 | [diff] [blame] | 2750 | /* Verify affinity of current kthread. */ |
| 2751 | WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2752 | |
| 2753 | /* Pick up current idle and NMI-nesting counter and check. */ |
| 2754 | cur = atomic_read(&rdtp->dynticks_idle); |
| 2755 | if (cur & 0x1) { |
| 2756 | *isidle = false; /* We are not idle! */ |
| 2757 | return; |
| 2758 | } |
| 2759 | smp_mb(); /* Read counters before timestamps. */ |
| 2760 | |
| 2761 | /* Pick up timestamps. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2762 | j = READ_ONCE(rdtp->dynticks_idle_jiffies); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2763 | /* If this CPU entered idle more recently, update maxj timestamp. */ |
| 2764 | if (ULONG_CMP_LT(*maxj, j)) |
| 2765 | *maxj = j; |
| 2766 | } |
| 2767 | |
| 2768 | /* |
| 2769 | * Is this the flavor of RCU that is handling full-system idle? |
| 2770 | */ |
| 2771 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) |
| 2772 | { |
Paul E. McKenney | 417e8d2 | 2014-07-21 11:26:54 -0700 | [diff] [blame] | 2773 | return rsp == rcu_state_p; |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2774 | } |
| 2775 | |
| 2776 | /* |
| 2777 | * Return a delay in jiffies based on the number of CPUs, rcu_node |
| 2778 | * leaf fanout, and jiffies tick rate. The idea is to allow larger |
| 2779 | * systems more time to transition to full-idle state in order to |
| 2780 | * avoid the cache thrashing that otherwise occur on the state variable. |
| 2781 | * Really small systems (less than a couple of tens of CPUs) should |
| 2782 | * instead use a single global atomically incremented counter, and later |
| 2783 | * versions of this will automatically reconfigure themselves accordingly. |
| 2784 | */ |
| 2785 | static unsigned long rcu_sysidle_delay(void) |
| 2786 | { |
| 2787 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) |
| 2788 | return 0; |
| 2789 | return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); |
| 2790 | } |
| 2791 | |
| 2792 | /* |
| 2793 | * Advance the full-system-idle state. This is invoked when all of |
| 2794 | * the non-timekeeping CPUs are idle. |
| 2795 | */ |
| 2796 | static void rcu_sysidle(unsigned long j) |
| 2797 | { |
| 2798 | /* Check the current state. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2799 | switch (READ_ONCE(full_sysidle_state)) { |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2800 | case RCU_SYSIDLE_NOT: |
| 2801 | |
| 2802 | /* First time all are idle, so note a short idle period. */ |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2803 | WRITE_ONCE(full_sysidle_state, RCU_SYSIDLE_SHORT); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2804 | break; |
| 2805 | |
| 2806 | case RCU_SYSIDLE_SHORT: |
| 2807 | |
| 2808 | /* |
| 2809 | * Idle for a bit, time to advance to next state? |
| 2810 | * cmpxchg failure means race with non-idle, let them win. |
| 2811 | */ |
| 2812 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) |
| 2813 | (void)cmpxchg(&full_sysidle_state, |
| 2814 | RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); |
| 2815 | break; |
| 2816 | |
| 2817 | case RCU_SYSIDLE_LONG: |
| 2818 | |
| 2819 | /* |
| 2820 | * Do an additional check pass before advancing to full. |
| 2821 | * cmpxchg failure means race with non-idle, let them win. |
| 2822 | */ |
| 2823 | if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) |
| 2824 | (void)cmpxchg(&full_sysidle_state, |
| 2825 | RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); |
| 2826 | break; |
| 2827 | |
| 2828 | default: |
| 2829 | break; |
| 2830 | } |
| 2831 | } |
| 2832 | |
| 2833 | /* |
| 2834 | * Found a non-idle non-timekeeping CPU, so kick the system-idle state |
| 2835 | * back to the beginning. |
| 2836 | */ |
| 2837 | static void rcu_sysidle_cancel(void) |
| 2838 | { |
| 2839 | smp_mb(); |
Paul E. McKenney | becb41b | 2014-04-07 13:34:07 -0700 | [diff] [blame] | 2840 | if (full_sysidle_state > RCU_SYSIDLE_SHORT) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2841 | WRITE_ONCE(full_sysidle_state, RCU_SYSIDLE_NOT); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2842 | } |
| 2843 | |
| 2844 | /* |
| 2845 | * Update the sysidle state based on the results of a force-quiescent-state |
| 2846 | * scan of the CPUs' dyntick-idle state. |
| 2847 | */ |
| 2848 | static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, |
| 2849 | unsigned long maxj, bool gpkt) |
| 2850 | { |
Paul E. McKenney | 417e8d2 | 2014-07-21 11:26:54 -0700 | [diff] [blame] | 2851 | if (rsp != rcu_state_p) |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2852 | return; /* Wrong flavor, ignore. */ |
| 2853 | if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) |
| 2854 | return; /* Running state machine from timekeeping CPU. */ |
| 2855 | if (isidle) |
| 2856 | rcu_sysidle(maxj); /* More idle! */ |
| 2857 | else |
| 2858 | rcu_sysidle_cancel(); /* Idle is over. */ |
| 2859 | } |
| 2860 | |
| 2861 | /* |
| 2862 | * Wrapper for rcu_sysidle_report() when called from the grace-period |
| 2863 | * kthread's context. |
| 2864 | */ |
| 2865 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, |
| 2866 | unsigned long maxj) |
| 2867 | { |
Paul E. McKenney | 663e131 | 2014-07-21 11:34:33 -0700 | [diff] [blame] | 2868 | /* If there are no nohz_full= CPUs, no need to track this. */ |
| 2869 | if (!tick_nohz_full_enabled()) |
| 2870 | return; |
| 2871 | |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2872 | rcu_sysidle_report(rsp, isidle, maxj, true); |
| 2873 | } |
| 2874 | |
| 2875 | /* Callback and function for forcing an RCU grace period. */ |
| 2876 | struct rcu_sysidle_head { |
| 2877 | struct rcu_head rh; |
| 2878 | int inuse; |
| 2879 | }; |
| 2880 | |
| 2881 | static void rcu_sysidle_cb(struct rcu_head *rhp) |
| 2882 | { |
| 2883 | struct rcu_sysidle_head *rshp; |
| 2884 | |
| 2885 | /* |
| 2886 | * The following memory barrier is needed to replace the |
| 2887 | * memory barriers that would normally be in the memory |
| 2888 | * allocator. |
| 2889 | */ |
| 2890 | smp_mb(); /* grace period precedes setting inuse. */ |
| 2891 | |
| 2892 | rshp = container_of(rhp, struct rcu_sysidle_head, rh); |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2893 | WRITE_ONCE(rshp->inuse, 0); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2894 | } |
| 2895 | |
| 2896 | /* |
| 2897 | * Check to see if the system is fully idle, other than the timekeeping CPU. |
Paul E. McKenney | 663e131 | 2014-07-21 11:34:33 -0700 | [diff] [blame] | 2898 | * The caller must have disabled interrupts. This is not intended to be |
| 2899 | * called unless tick_nohz_full_enabled(). |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2900 | */ |
| 2901 | bool rcu_sys_is_idle(void) |
| 2902 | { |
| 2903 | static struct rcu_sysidle_head rsh; |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2904 | int rss = READ_ONCE(full_sysidle_state); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2905 | |
| 2906 | if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) |
| 2907 | return false; |
| 2908 | |
| 2909 | /* Handle small-system case by doing a full scan of CPUs. */ |
| 2910 | if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { |
| 2911 | int oldrss = rss - 1; |
| 2912 | |
| 2913 | /* |
| 2914 | * One pass to advance to each state up to _FULL. |
| 2915 | * Give up if any pass fails to advance the state. |
| 2916 | */ |
| 2917 | while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { |
| 2918 | int cpu; |
| 2919 | bool isidle = true; |
| 2920 | unsigned long maxj = jiffies - ULONG_MAX / 4; |
| 2921 | struct rcu_data *rdp; |
| 2922 | |
| 2923 | /* Scan all the CPUs looking for nonidle CPUs. */ |
| 2924 | for_each_possible_cpu(cpu) { |
Paul E. McKenney | 417e8d2 | 2014-07-21 11:26:54 -0700 | [diff] [blame] | 2925 | rdp = per_cpu_ptr(rcu_state_p->rda, cpu); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2926 | rcu_sysidle_check_cpu(rdp, &isidle, &maxj); |
| 2927 | if (!isidle) |
| 2928 | break; |
| 2929 | } |
Paul E. McKenney | 417e8d2 | 2014-07-21 11:26:54 -0700 | [diff] [blame] | 2930 | rcu_sysidle_report(rcu_state_p, isidle, maxj, false); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2931 | oldrss = rss; |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 2932 | rss = READ_ONCE(full_sysidle_state); |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2933 | } |
| 2934 | } |
| 2935 | |
| 2936 | /* If this is the first observation of an idle period, record it. */ |
| 2937 | if (rss == RCU_SYSIDLE_FULL) { |
| 2938 | rss = cmpxchg(&full_sysidle_state, |
| 2939 | RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); |
| 2940 | return rss == RCU_SYSIDLE_FULL; |
| 2941 | } |
| 2942 | |
| 2943 | smp_mb(); /* ensure rss load happens before later caller actions. */ |
| 2944 | |
| 2945 | /* If already fully idle, tell the caller (in case of races). */ |
| 2946 | if (rss == RCU_SYSIDLE_FULL_NOTED) |
| 2947 | return true; |
| 2948 | |
| 2949 | /* |
| 2950 | * If we aren't there yet, and a grace period is not in flight, |
| 2951 | * initiate a grace period. Either way, tell the caller that |
| 2952 | * we are not there yet. We use an xchg() rather than an assignment |
| 2953 | * to make up for the memory barriers that would otherwise be |
| 2954 | * provided by the memory allocator. |
| 2955 | */ |
| 2956 | if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && |
Paul E. McKenney | 417e8d2 | 2014-07-21 11:26:54 -0700 | [diff] [blame] | 2957 | !rcu_gp_in_progress(rcu_state_p) && |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2958 | !rsh.inuse && xchg(&rsh.inuse, 1) == 0) |
| 2959 | call_rcu(&rsh.rh, rcu_sysidle_cb); |
| 2960 | return false; |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2961 | } |
| 2962 | |
| 2963 | /* |
Paul E. McKenney | 2333210 | 2013-06-21 12:34:33 -0700 | [diff] [blame] | 2964 | * Initialize dynticks sysidle state for CPUs coming online. |
| 2965 | */ |
| 2966 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) |
| 2967 | { |
| 2968 | rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; |
| 2969 | } |
| 2970 | |
| 2971 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
| 2972 | |
Christoph Lameter | 28ced79 | 2014-09-02 14:13:44 -0700 | [diff] [blame] | 2973 | static void rcu_sysidle_enter(int irq) |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2974 | { |
| 2975 | } |
| 2976 | |
Christoph Lameter | 28ced79 | 2014-09-02 14:13:44 -0700 | [diff] [blame] | 2977 | static void rcu_sysidle_exit(int irq) |
Paul E. McKenney | eb348b8 | 2013-06-21 13:00:57 -0700 | [diff] [blame] | 2978 | { |
| 2979 | } |
| 2980 | |
Paul E. McKenney | 0edd1b1 | 2013-06-21 16:37:22 -0700 | [diff] [blame] | 2981 | static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, |
| 2982 | unsigned long *maxj) |
| 2983 | { |
| 2984 | } |
| 2985 | |
| 2986 | static bool is_sysidle_rcu_state(struct rcu_state *rsp) |
| 2987 | { |
| 2988 | return false; |
| 2989 | } |
| 2990 | |
| 2991 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, |
| 2992 | unsigned long maxj) |
| 2993 | { |
| 2994 | } |
| 2995 | |
Paul E. McKenney | 2333210 | 2013-06-21 12:34:33 -0700 | [diff] [blame] | 2996 | static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) |
| 2997 | { |
| 2998 | } |
| 2999 | |
| 3000 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 3001 | |
| 3002 | /* |
| 3003 | * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the |
| 3004 | * grace-period kthread will do force_quiescent_state() processing? |
| 3005 | * The idea is to avoid waking up RCU core processing on such a |
| 3006 | * CPU unless the grace period has extended for too long. |
| 3007 | * |
| 3008 | * This code relies on the fact that all NO_HZ_FULL CPUs are also |
Paul Bolle | 52e2bb9 | 2014-02-09 14:35:11 +0100 | [diff] [blame] | 3009 | * CONFIG_RCU_NOCB_CPU CPUs. |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 3010 | */ |
| 3011 | static bool rcu_nohz_full_cpu(struct rcu_state *rsp) |
| 3012 | { |
| 3013 | #ifdef CONFIG_NO_HZ_FULL |
| 3014 | if (tick_nohz_full_cpu(smp_processor_id()) && |
| 3015 | (!rcu_gp_in_progress(rsp) || |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 3016 | ULONG_CMP_LT(jiffies, READ_ONCE(rsp->gp_start) + HZ))) |
Joe Perches | 5ce035f | 2015-03-30 16:46:16 -0700 | [diff] [blame] | 3017 | return true; |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 3018 | #endif /* #ifdef CONFIG_NO_HZ_FULL */ |
Joe Perches | 5ce035f | 2015-03-30 16:46:16 -0700 | [diff] [blame] | 3019 | return false; |
Paul E. McKenney | a096932 | 2013-11-08 09:03:10 -0800 | [diff] [blame] | 3020 | } |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 3021 | |
| 3022 | /* |
| 3023 | * Bind the grace-period kthread for the sysidle flavor of RCU to the |
| 3024 | * timekeeping CPU. |
| 3025 | */ |
| 3026 | static void rcu_bind_gp_kthread(void) |
| 3027 | { |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 3028 | int __maybe_unused cpu; |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 3029 | |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 3030 | if (!tick_nohz_full_enabled()) |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 3031 | return; |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 3032 | #ifdef CONFIG_NO_HZ_FULL_SYSIDLE |
| 3033 | cpu = tick_do_timer_cpu; |
Paul E. McKenney | 5871968 | 2015-02-24 11:05:36 -0800 | [diff] [blame] | 3034 | if (cpu >= 0 && cpu < nr_cpu_ids) |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 3035 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 3036 | #else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
Paul E. McKenney | 5871968 | 2015-02-24 11:05:36 -0800 | [diff] [blame] | 3037 | housekeeping_affine(current); |
Paul E. McKenney | c0f489d | 2014-06-04 13:46:03 -0700 | [diff] [blame] | 3038 | #endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ |
Paul E. McKenney | 5057f55e5 | 2014-04-01 11:20:36 -0700 | [diff] [blame] | 3039 | } |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 3040 | |
| 3041 | /* Record the current task on dyntick-idle entry. */ |
| 3042 | static void rcu_dynticks_task_enter(void) |
| 3043 | { |
| 3044 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 3045 | WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id()); |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 3046 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ |
| 3047 | } |
| 3048 | |
| 3049 | /* Record no current task on dyntick-idle exit. */ |
| 3050 | static void rcu_dynticks_task_exit(void) |
| 3051 | { |
| 3052 | #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) |
Paul E. McKenney | 7d0ae80 | 2015-03-03 14:57:58 -0800 | [diff] [blame] | 3053 | WRITE_ONCE(current->rcu_tasks_idle_cpu, -1); |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 3054 | #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */ |
| 3055 | } |