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Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001/*
2 * Read-Copy Update mechanism for mutual exclusion
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
Paul E. McKenney87de1cf2013-12-03 10:02:52 -080015 * along with this program; if not, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010017 *
18 * Copyright IBM Corporation, 2008
19 *
20 * Authors: Dipankar Sarma <dipankar@in.ibm.com>
21 * Manfred Spraul <manfred@colorfullife.com>
22 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version
23 *
24 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
25 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
26 *
27 * For detailed explanation of Read-Copy Update mechanism see -
Paul E. McKenneya71fca52009-09-18 10:28:19 -070028 * Documentation/RCU
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010029 */
30#include <linux/types.h>
31#include <linux/kernel.h>
32#include <linux/init.h>
33#include <linux/spinlock.h>
34#include <linux/smp.h>
35#include <linux/rcupdate.h>
36#include <linux/interrupt.h>
37#include <linux/sched.h>
Ingo Molnarc1dc0b92009-08-02 11:28:21 +020038#include <linux/nmi.h>
Paul E. McKenney8826f3b2011-05-11 05:41:41 -070039#include <linux/atomic.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010040#include <linux/bitops.h>
Paul Gortmaker9984de12011-05-23 14:51:41 -040041#include <linux/export.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010042#include <linux/completion.h>
43#include <linux/moduleparam.h>
Paul E. McKenney4102ada2013-10-08 20:23:47 -070044#include <linux/module.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010045#include <linux/percpu.h>
46#include <linux/notifier.h>
47#include <linux/cpu.h>
48#include <linux/mutex.h>
49#include <linux/time.h>
Paul E. McKenneybbad9372010-04-02 16:17:17 -070050#include <linux/kernel_stat.h>
Paul E. McKenneya26ac242011-01-12 14:10:23 -080051#include <linux/wait.h>
52#include <linux/kthread.h>
Linus Torvalds268bb0c2011-05-20 12:50:29 -070053#include <linux/prefetch.h>
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -080054#include <linux/delay.h>
55#include <linux/stop_machine.h>
Paul E. McKenney661a85d2012-07-07 05:57:03 -070056#include <linux/random.h>
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -040057#include <linux/ftrace_event.h>
Borislav Petkovd1d74d12013-04-22 00:12:42 +020058#include <linux/suspend.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010059
Paul E. McKenney4102ada2013-10-08 20:23:47 -070060#include "tree.h"
Paul E. McKenney29c00b42011-06-17 15:53:19 -070061#include "rcu.h"
Paul E. McKenney9f77da92009-08-22 13:56:45 -070062
Paul E. McKenney4102ada2013-10-08 20:23:47 -070063MODULE_ALIAS("rcutree");
64#ifdef MODULE_PARAM_PREFIX
65#undef MODULE_PARAM_PREFIX
66#endif
67#define MODULE_PARAM_PREFIX "rcutree."
68
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010069/* Data structures. */
70
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -070071static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
Paul E. McKenney394f2762012-06-26 17:00:35 -070072static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
Peter Zijlstra88b91c72009-10-26 10:24:31 -070073
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -040074/*
75 * In order to export the rcu_state name to the tracing tools, it
76 * needs to be added in the __tracepoint_string section.
77 * This requires defining a separate variable tp_<sname>_varname
78 * that points to the string being used, and this will allow
79 * the tracing userspace tools to be able to decipher the string
80 * address to the matching string.
81 */
Steven Rostedt (Red Hat)a41bfeb2013-07-12 17:00:28 -040082#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -040083static char sname##_varname[] = #sname; \
84static const char *tp_##sname##_varname __used __tracepoint_string = sname##_varname; \
Steven Rostedt (Red Hat)a41bfeb2013-07-12 17:00:28 -040085struct rcu_state sname##_state = { \
Paul E. McKenney6c90cc72012-05-28 19:41:41 -070086 .level = { &sname##_state.node[0] }, \
Paul E. McKenney037b64e2012-05-28 23:26:01 -070087 .call = cr, \
Paul E. McKenneyaf446b72011-09-10 21:54:08 -070088 .fqs_state = RCU_GP_IDLE, \
Paul E. McKenney42c35332012-09-28 10:49:58 -070089 .gpnum = 0UL - 300UL, \
90 .completed = 0UL - 300UL, \
Paul E. McKenney7b2e6012012-10-08 10:54:03 -070091 .orphan_lock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.orphan_lock), \
Paul E. McKenney6c90cc72012-05-28 19:41:41 -070092 .orphan_nxttail = &sname##_state.orphan_nxtlist, \
93 .orphan_donetail = &sname##_state.orphan_donelist, \
Paul E. McKenney7be7f0b2012-05-29 05:18:53 -070094 .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
Paul E. McKenneya4fbe352012-10-07 08:36:12 -070095 .onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -040096 .name = sname##_varname, \
Paul E. McKenneya4889852012-12-03 08:16:28 -080097 .abbr = sabbr, \
Steven Rostedt (Red Hat)a41bfeb2013-07-12 17:00:28 -040098}; \
99DEFINE_PER_CPU(struct rcu_data, sname##_data)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100100
Steven Rostedt (Red Hat)a41bfeb2013-07-12 17:00:28 -0400101RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
102RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100103
Paul E. McKenney27f4d282011-02-07 12:47:15 -0800104static struct rcu_state *rcu_state;
Paul E. McKenney6ce75a22012-06-12 11:01:13 -0700105LIST_HEAD(rcu_struct_flavors);
Paul E. McKenney27f4d282011-02-07 12:47:15 -0800106
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -0700107/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
108static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
Paul E. McKenney7e5c2df2012-07-01 15:42:33 -0700109module_param(rcu_fanout_leaf, int, 0444);
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -0700110int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
111static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */
112 NUM_RCU_LVL_0,
113 NUM_RCU_LVL_1,
114 NUM_RCU_LVL_2,
115 NUM_RCU_LVL_3,
116 NUM_RCU_LVL_4,
117};
118int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
119
Paul E. McKenneyb0d30412011-07-10 15:57:35 -0700120/*
121 * The rcu_scheduler_active variable transitions from zero to one just
122 * before the first task is spawned. So when this variable is zero, RCU
123 * can assume that there is but one task, allowing RCU to (for example)
Cody P Schaferb44f6652013-01-04 12:59:40 -0500124 * optimize synchronize_sched() to a simple barrier(). When this variable
Paul E. McKenneyb0d30412011-07-10 15:57:35 -0700125 * is one, RCU must actually do all the hard work required to detect real
126 * grace periods. This variable is also used to suppress boot-time false
127 * positives from lockdep-RCU error checking.
128 */
Paul E. McKenneybbad9372010-04-02 16:17:17 -0700129int rcu_scheduler_active __read_mostly;
130EXPORT_SYMBOL_GPL(rcu_scheduler_active);
131
Paul E. McKenneyb0d30412011-07-10 15:57:35 -0700132/*
133 * The rcu_scheduler_fully_active variable transitions from zero to one
134 * during the early_initcall() processing, which is after the scheduler
135 * is capable of creating new tasks. So RCU processing (for example,
136 * creating tasks for RCU priority boosting) must be delayed until after
137 * rcu_scheduler_fully_active transitions from zero to one. We also
138 * currently delay invocation of any RCU callbacks until after this point.
139 *
140 * It might later prove better for people registering RCU callbacks during
141 * early boot to take responsibility for these callbacks, but one step at
142 * a time.
143 */
144static int rcu_scheduler_fully_active __read_mostly;
145
Paul E. McKenneya46e0892011-06-15 15:47:09 -0700146#ifdef CONFIG_RCU_BOOST
147
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100148/*
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800149 * Control variables for per-CPU and per-rcu_node kthreads. These
150 * handle all flavors of RCU.
151 */
152static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
Paul E. McKenneyd71df902011-03-29 17:48:28 -0700153DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
Paul E. McKenney5ece5ba2011-04-22 18:08:51 -0700154DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
Paul E. McKenneyd71df902011-03-29 17:48:28 -0700155DEFINE_PER_CPU(char, rcu_cpu_has_work);
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800156
Paul E. McKenneya46e0892011-06-15 15:47:09 -0700157#endif /* #ifdef CONFIG_RCU_BOOST */
158
Thomas Gleixner5d01bbd2012-07-16 10:42:35 +0000159static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
Paul E. McKenneya46e0892011-06-15 15:47:09 -0700160static void invoke_rcu_core(void);
161static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800162
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800163/*
Paul E. McKenney4a298652011-04-03 21:33:51 -0700164 * Track the rcutorture test sequence number and the update version
165 * number within a given test. The rcutorture_testseq is incremented
166 * on every rcutorture module load and unload, so has an odd value
167 * when a test is running. The rcutorture_vernum is set to zero
168 * when rcutorture starts and is incremented on each rcutorture update.
169 * These variables enable correlating rcutorture output with the
170 * RCU tracing information.
171 */
172unsigned long rcutorture_testseq;
173unsigned long rcutorture_vernum;
174
175/*
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700176 * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
177 * permit this function to be invoked without holding the root rcu_node
178 * structure's ->lock, but of course results can be subject to change.
179 */
180static int rcu_gp_in_progress(struct rcu_state *rsp)
181{
182 return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
183}
184
185/*
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700186 * Note a quiescent state. Because we do not need to know
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100187 * how many quiescent states passed, just if there was at least
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700188 * one since the start of the grace period, this just sets a flag.
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700189 * The caller must have disabled preemption.
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100190 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700191void rcu_sched_qs(int cpu)
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100192{
Paul E. McKenney25502a62010-04-01 17:37:01 -0700193 struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700194
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700195 if (rdp->passed_quiesce == 0)
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400196 trace_rcu_grace_period(TPS("rcu_sched"), rdp->gpnum, TPS("cpuqs"));
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700197 rdp->passed_quiesce = 1;
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100198}
199
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700200void rcu_bh_qs(int cpu)
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100201{
Paul E. McKenney25502a62010-04-01 17:37:01 -0700202 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700203
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700204 if (rdp->passed_quiesce == 0)
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400205 trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs"));
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700206 rdp->passed_quiesce = 1;
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100207}
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100208
Paul E. McKenney25502a62010-04-01 17:37:01 -0700209/*
210 * Note a context switch. This is a quiescent state for RCU-sched,
211 * and requires special handling for preemptible RCU.
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700212 * The caller must have disabled preemption.
Paul E. McKenney25502a62010-04-01 17:37:01 -0700213 */
214void rcu_note_context_switch(int cpu)
215{
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400216 trace_rcu_utilization(TPS("Start context switch"));
Paul E. McKenney25502a62010-04-01 17:37:01 -0700217 rcu_sched_qs(cpu);
Paul E. McKenneycba6d0d2012-07-02 07:08:42 -0700218 rcu_preempt_note_context_switch(cpu);
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400219 trace_rcu_utilization(TPS("End context switch"));
Paul E. McKenney25502a62010-04-01 17:37:01 -0700220}
Gleb Natapov29ce8312011-05-04 16:31:03 +0300221EXPORT_SYMBOL_GPL(rcu_note_context_switch);
Paul E. McKenney25502a62010-04-01 17:37:01 -0700222
Paul E. McKenney01896f72013-08-18 12:14:32 -0700223static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
Paul E. McKenney29e37d82011-11-17 16:55:56 -0800224 .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700225 .dynticks = ATOMIC_INIT(1),
Paul E. McKenney23332102013-06-21 12:34:33 -0700226#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
227 .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE,
228 .dynticks_idle = ATOMIC_INIT(1),
229#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
Paul E. McKenney90a4d2c2009-01-04 11:41:11 -0800230};
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100231
Eric Dumazet878d7432012-10-18 04:55:36 -0700232static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */
233static long qhimark = 10000; /* If this many pending, ignore blimit. */
234static long qlowmark = 100; /* Once only this many pending, use blimit. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100235
Eric Dumazet878d7432012-10-18 04:55:36 -0700236module_param(blimit, long, 0444);
237module_param(qhimark, long, 0444);
238module_param(qlowmark, long, 0444);
Paul E. McKenney3d76c082009-09-28 07:46:32 -0700239
Paul E. McKenney026ad282013-04-03 22:14:11 -0700240static ulong jiffies_till_first_fqs = ULONG_MAX;
241static ulong jiffies_till_next_fqs = ULONG_MAX;
Paul E. McKenneyd40011f2012-06-26 20:45:57 -0700242
243module_param(jiffies_till_first_fqs, ulong, 0644);
244module_param(jiffies_till_next_fqs, ulong, 0644);
245
Paul E. McKenney48a76392014-03-11 13:02:16 -0700246static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
Paul E. McKenney910ee452012-12-31 02:24:21 -0800247 struct rcu_data *rdp);
Paul E. McKenney217af2a2013-06-21 15:39:06 -0700248static void force_qs_rnp(struct rcu_state *rsp,
249 int (*f)(struct rcu_data *rsp, bool *isidle,
250 unsigned long *maxj),
251 bool *isidle, unsigned long *maxj);
Paul E. McKenney4cdfc172012-06-22 17:06:26 -0700252static void force_quiescent_state(struct rcu_state *rsp);
Paul E. McKenneya1572292009-08-22 13:56:51 -0700253static int rcu_pending(int cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100254
255/*
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700256 * Return the number of RCU-sched batches processed thus far for debug & stats.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100257 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700258long rcu_batches_completed_sched(void)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100259{
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700260 return rcu_sched_state.completed;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100261}
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700262EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100263
264/*
265 * Return the number of RCU BH batches processed thus far for debug & stats.
266 */
267long rcu_batches_completed_bh(void)
268{
269 return rcu_bh_state.completed;
270}
271EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
272
273/*
Paul E. McKenneybf66f182010-01-04 15:09:10 -0800274 * Force a quiescent state for RCU BH.
275 */
276void rcu_bh_force_quiescent_state(void)
277{
Paul E. McKenney4cdfc172012-06-22 17:06:26 -0700278 force_quiescent_state(&rcu_bh_state);
Paul E. McKenneybf66f182010-01-04 15:09:10 -0800279}
280EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
281
282/*
Paul E. McKenney4a298652011-04-03 21:33:51 -0700283 * Record the number of times rcutorture tests have been initiated and
284 * terminated. This information allows the debugfs tracing stats to be
285 * correlated to the rcutorture messages, even when the rcutorture module
286 * is being repeatedly loaded and unloaded. In other words, we cannot
287 * store this state in rcutorture itself.
288 */
289void rcutorture_record_test_transition(void)
290{
291 rcutorture_testseq++;
292 rcutorture_vernum = 0;
293}
294EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
295
296/*
297 * Record the number of writer passes through the current rcutorture test.
298 * This is also used to correlate debugfs tracing stats with the rcutorture
299 * messages.
300 */
301void rcutorture_record_progress(unsigned long vernum)
302{
303 rcutorture_vernum++;
304}
305EXPORT_SYMBOL_GPL(rcutorture_record_progress);
306
307/*
Paul E. McKenneybf66f182010-01-04 15:09:10 -0800308 * Force a quiescent state for RCU-sched.
309 */
310void rcu_sched_force_quiescent_state(void)
311{
Paul E. McKenney4cdfc172012-06-22 17:06:26 -0700312 force_quiescent_state(&rcu_sched_state);
Paul E. McKenneybf66f182010-01-04 15:09:10 -0800313}
314EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
315
316/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100317 * Does the CPU have callbacks ready to be invoked?
318 */
319static int
320cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
321{
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -0700322 return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL] &&
323 rdp->nxttail[RCU_DONE_TAIL] != NULL;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100324}
325
326/*
Paul E. McKenney365187f2014-03-10 10:55:52 -0700327 * Return the root node of the specified rcu_state structure.
328 */
329static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
330{
331 return &rsp->node[0];
332}
333
334/*
335 * Is there any need for future grace periods?
336 * Interrupts must be disabled. If the caller does not hold the root
337 * rnp_node structure's ->lock, the results are advisory only.
338 */
339static int rcu_future_needs_gp(struct rcu_state *rsp)
340{
341 struct rcu_node *rnp = rcu_get_root(rsp);
342 int idx = (ACCESS_ONCE(rnp->completed) + 1) & 0x1;
343 int *fp = &rnp->need_future_gp[idx];
344
345 return ACCESS_ONCE(*fp);
346}
347
348/*
Paul E. McKenneydc35c892012-12-03 13:52:00 -0800349 * Does the current CPU require a not-yet-started grace period?
350 * The caller must have disabled interrupts to prevent races with
351 * normal callback registry.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100352 */
353static int
354cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
355{
Paul E. McKenneydc35c892012-12-03 13:52:00 -0800356 int i;
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -0700357
Paul E. McKenneydc35c892012-12-03 13:52:00 -0800358 if (rcu_gp_in_progress(rsp))
359 return 0; /* No, a grace period is already in progress. */
Paul E. McKenney365187f2014-03-10 10:55:52 -0700360 if (rcu_future_needs_gp(rsp))
Paul E. McKenney34ed62462013-01-07 13:37:42 -0800361 return 1; /* Yes, a no-CBs CPU needs one. */
Paul E. McKenneydc35c892012-12-03 13:52:00 -0800362 if (!rdp->nxttail[RCU_NEXT_TAIL])
363 return 0; /* No, this is a no-CBs (or offline) CPU. */
364 if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
365 return 1; /* Yes, this CPU has newly registered callbacks. */
366 for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
367 if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
368 ULONG_CMP_LT(ACCESS_ONCE(rsp->completed),
369 rdp->nxtcompleted[i]))
370 return 1; /* Yes, CBs for future grace period. */
371 return 0; /* No grace period needed. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100372}
373
374/*
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700375 * rcu_eqs_enter_common - current CPU is moving towards extended quiescent state
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100376 *
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700377 * If the new value of the ->dynticks_nesting counter now is zero,
378 * we really have entered idle, and must do the appropriate accounting.
379 * The caller must have disabled interrupts.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100380 */
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700381static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
382 bool user)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100383{
Paul E. McKenney96d3fd02013-10-04 14:33:34 -0700384 struct rcu_state *rsp;
385 struct rcu_data *rdp;
386
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400387 trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
Paul E. McKenneycb349ca2012-09-04 17:35:31 -0700388 if (!user && !is_idle_task(current)) {
Paul E. McKenney289828e2013-08-31 19:23:29 -0700389 struct task_struct *idle __maybe_unused =
390 idle_task(smp_processor_id());
Paul E. McKenney0989cb42011-11-01 08:57:21 -0700391
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400392 trace_rcu_dyntick(TPS("Error on entry: not idle task"), oldval, 0);
Paul E. McKenneybf1304e2012-05-09 15:55:39 -0700393 ftrace_dump(DUMP_ORIG);
Paul E. McKenney0989cb42011-11-01 08:57:21 -0700394 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
395 current->pid, current->comm,
396 idle->pid, idle->comm); /* must be idle task! */
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700397 }
Paul E. McKenney96d3fd02013-10-04 14:33:34 -0700398 for_each_rcu_flavor(rsp) {
399 rdp = this_cpu_ptr(rsp->rda);
400 do_nocb_deferred_wakeup(rdp);
401 }
Paul E. McKenneyaea1b352011-11-02 06:54:54 -0700402 rcu_prepare_for_idle(smp_processor_id());
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700403 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
404 smp_mb__before_atomic_inc(); /* See above. */
405 atomic_inc(&rdtp->dynticks);
406 smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
407 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
Paul E. McKenneyc44e2cd2012-01-12 13:08:18 -0800408
409 /*
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700410 * It is illegal to enter an extended quiescent state while
Paul E. McKenneyc44e2cd2012-01-12 13:08:18 -0800411 * in an RCU read-side critical section.
412 */
413 rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
414 "Illegal idle entry in RCU read-side critical section.");
415 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
416 "Illegal idle entry in RCU-bh read-side critical section.");
417 rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
418 "Illegal idle entry in RCU-sched read-side critical section.");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100419}
420
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700421/*
422 * Enter an RCU extended quiescent state, which can be either the
423 * idle loop or adaptive-tickless usermode execution.
424 */
425static void rcu_eqs_enter(bool user)
426{
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700427 long long oldval;
428 struct rcu_dynticks *rdtp;
429
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700430 rdtp = this_cpu_ptr(&rcu_dynticks);
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700431 oldval = rdtp->dynticks_nesting;
432 WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
Paul E. McKenney3a592402013-10-04 18:48:55 -0700433 if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) {
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700434 rdtp->dynticks_nesting = 0;
Paul E. McKenney3a592402013-10-04 18:48:55 -0700435 rcu_eqs_enter_common(rdtp, oldval, user);
436 } else {
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700437 rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
Paul E. McKenney3a592402013-10-04 18:48:55 -0700438 }
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700439}
440
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700441/**
442 * rcu_idle_enter - inform RCU that current CPU is entering idle
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100443 *
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700444 * Enter idle mode, in other words, -leave- the mode in which RCU
445 * read-side critical sections can occur. (Though RCU read-side
446 * critical sections can occur in irq handlers in idle, a possibility
447 * handled by irq_enter() and irq_exit().)
448 *
449 * We crowbar the ->dynticks_nesting field to zero to allow for
450 * the possibility of usermode upcalls having messed up our count
451 * of interrupt nesting level during the prior busy period.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100452 */
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700453void rcu_idle_enter(void)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100454{
Frederic Weisbeckerc5d900b2012-07-11 20:26:31 +0200455 unsigned long flags;
456
457 local_irq_save(flags);
Paul E. McKenneycb349ca2012-09-04 17:35:31 -0700458 rcu_eqs_enter(false);
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700459 rcu_sysidle_enter(this_cpu_ptr(&rcu_dynticks), 0);
Frederic Weisbeckerc5d900b2012-07-11 20:26:31 +0200460 local_irq_restore(flags);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700461}
Paul E. McKenney8a2ecf42012-02-02 15:42:04 -0800462EXPORT_SYMBOL_GPL(rcu_idle_enter);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700463
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200464#ifdef CONFIG_RCU_USER_QS
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700465/**
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700466 * rcu_user_enter - inform RCU that we are resuming userspace.
467 *
468 * Enter RCU idle mode right before resuming userspace. No use of RCU
469 * is permitted between this call and rcu_user_exit(). This way the
470 * CPU doesn't need to maintain the tick for RCU maintenance purposes
471 * when the CPU runs in userspace.
472 */
473void rcu_user_enter(void)
474{
Frederic Weisbecker91d1aa432012-11-27 19:33:25 +0100475 rcu_eqs_enter(1);
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700476}
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200477#endif /* CONFIG_RCU_USER_QS */
Frederic Weisbecker19dd1592012-06-04 16:42:35 -0700478
479/**
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700480 * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
481 *
482 * Exit from an interrupt handler, which might possibly result in entering
483 * idle mode, in other words, leaving the mode in which read-side critical
484 * sections can occur.
485 *
486 * This code assumes that the idle loop never does anything that might
487 * result in unbalanced calls to irq_enter() and irq_exit(). If your
488 * architecture violates this assumption, RCU will give you what you
489 * deserve, good and hard. But very infrequently and irreproducibly.
490 *
491 * Use things like work queues to work around this limitation.
492 *
493 * You have been warned.
494 */
495void rcu_irq_exit(void)
496{
497 unsigned long flags;
Paul E. McKenney4145fa72011-10-31 15:01:54 -0700498 long long oldval;
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700499 struct rcu_dynticks *rdtp;
500
501 local_irq_save(flags);
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700502 rdtp = this_cpu_ptr(&rcu_dynticks);
Paul E. McKenney4145fa72011-10-31 15:01:54 -0700503 oldval = rdtp->dynticks_nesting;
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700504 rdtp->dynticks_nesting--;
505 WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
Frederic Weisbeckerb6fc6022011-11-28 16:18:56 -0800506 if (rdtp->dynticks_nesting)
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400507 trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting);
Frederic Weisbeckerb6fc6022011-11-28 16:18:56 -0800508 else
Paul E. McKenneycb349ca2012-09-04 17:35:31 -0700509 rcu_eqs_enter_common(rdtp, oldval, true);
Paul E. McKenneyeb348b82013-06-21 13:00:57 -0700510 rcu_sysidle_enter(rdtp, 1);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700511 local_irq_restore(flags);
512}
513
514/*
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700515 * rcu_eqs_exit_common - current CPU moving away from extended quiescent state
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700516 *
517 * If the new value of the ->dynticks_nesting counter was previously zero,
518 * we really have exited idle, and must do the appropriate accounting.
519 * The caller must have disabled interrupts.
520 */
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700521static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
522 int user)
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700523{
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700524 smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
525 atomic_inc(&rdtp->dynticks);
526 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
527 smp_mb__after_atomic_inc(); /* See above. */
528 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
Paul E. McKenney7cb92492011-11-28 12:28:34 -0800529 rcu_cleanup_after_idle(smp_processor_id());
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400530 trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
Paul E. McKenneycb349ca2012-09-04 17:35:31 -0700531 if (!user && !is_idle_task(current)) {
Paul E. McKenney289828e2013-08-31 19:23:29 -0700532 struct task_struct *idle __maybe_unused =
533 idle_task(smp_processor_id());
Paul E. McKenney0989cb42011-11-01 08:57:21 -0700534
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400535 trace_rcu_dyntick(TPS("Error on exit: not idle task"),
Paul E. McKenney4145fa72011-10-31 15:01:54 -0700536 oldval, rdtp->dynticks_nesting);
Paul E. McKenneybf1304e2012-05-09 15:55:39 -0700537 ftrace_dump(DUMP_ORIG);
Paul E. McKenney0989cb42011-11-01 08:57:21 -0700538 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
539 current->pid, current->comm,
540 idle->pid, idle->comm); /* must be idle task! */
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700541 }
542}
543
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700544/*
545 * Exit an RCU extended quiescent state, which can be either the
546 * idle loop or adaptive-tickless usermode execution.
547 */
548static void rcu_eqs_exit(bool user)
549{
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700550 struct rcu_dynticks *rdtp;
551 long long oldval;
552
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700553 rdtp = this_cpu_ptr(&rcu_dynticks);
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700554 oldval = rdtp->dynticks_nesting;
555 WARN_ON_ONCE(oldval < 0);
Paul E. McKenney3a592402013-10-04 18:48:55 -0700556 if (oldval & DYNTICK_TASK_NEST_MASK) {
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700557 rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
Paul E. McKenney3a592402013-10-04 18:48:55 -0700558 } else {
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700559 rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
Paul E. McKenney3a592402013-10-04 18:48:55 -0700560 rcu_eqs_exit_common(rdtp, oldval, user);
561 }
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700562}
563
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700564/**
565 * rcu_idle_exit - inform RCU that current CPU is leaving idle
566 *
567 * Exit idle mode, in other words, -enter- the mode in which RCU
568 * read-side critical sections can occur.
569 *
Paul E. McKenney29e37d82011-11-17 16:55:56 -0800570 * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
Paul E. McKenney4145fa72011-10-31 15:01:54 -0700571 * allow for the possibility of usermode upcalls messing up our count
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700572 * of interrupt nesting level during the busy period that is just
573 * now starting.
574 */
575void rcu_idle_exit(void)
576{
Frederic Weisbeckerc5d900b2012-07-11 20:26:31 +0200577 unsigned long flags;
578
579 local_irq_save(flags);
Paul E. McKenneycb349ca2012-09-04 17:35:31 -0700580 rcu_eqs_exit(false);
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700581 rcu_sysidle_exit(this_cpu_ptr(&rcu_dynticks), 0);
Frederic Weisbeckerc5d900b2012-07-11 20:26:31 +0200582 local_irq_restore(flags);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700583}
Paul E. McKenney8a2ecf42012-02-02 15:42:04 -0800584EXPORT_SYMBOL_GPL(rcu_idle_exit);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700585
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200586#ifdef CONFIG_RCU_USER_QS
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700587/**
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700588 * rcu_user_exit - inform RCU that we are exiting userspace.
589 *
590 * Exit RCU idle mode while entering the kernel because it can
591 * run a RCU read side critical section anytime.
592 */
593void rcu_user_exit(void)
594{
Frederic Weisbecker91d1aa432012-11-27 19:33:25 +0100595 rcu_eqs_exit(1);
Frederic Weisbeckeradf50912012-06-28 11:20:21 -0700596}
Frederic Weisbecker2b1d5022012-07-11 20:26:30 +0200597#endif /* CONFIG_RCU_USER_QS */
Frederic Weisbecker19dd1592012-06-04 16:42:35 -0700598
599/**
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700600 * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
601 *
602 * Enter an interrupt handler, which might possibly result in exiting
603 * idle mode, in other words, entering the mode in which read-side critical
604 * sections can occur.
605 *
606 * Note that the Linux kernel is fully capable of entering an interrupt
607 * handler that it never exits, for example when doing upcalls to
608 * user mode! This code assumes that the idle loop never does upcalls to
609 * user mode. If your architecture does do upcalls from the idle loop (or
610 * does anything else that results in unbalanced calls to the irq_enter()
611 * and irq_exit() functions), RCU will give you what you deserve, good
612 * and hard. But very infrequently and irreproducibly.
613 *
614 * Use things like work queues to work around this limitation.
615 *
616 * You have been warned.
617 */
618void rcu_irq_enter(void)
619{
620 unsigned long flags;
621 struct rcu_dynticks *rdtp;
622 long long oldval;
623
624 local_irq_save(flags);
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700625 rdtp = this_cpu_ptr(&rcu_dynticks);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700626 oldval = rdtp->dynticks_nesting;
627 rdtp->dynticks_nesting++;
628 WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
Frederic Weisbeckerb6fc6022011-11-28 16:18:56 -0800629 if (oldval)
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400630 trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting);
Frederic Weisbeckerb6fc6022011-11-28 16:18:56 -0800631 else
Paul E. McKenneycb349ca2012-09-04 17:35:31 -0700632 rcu_eqs_exit_common(rdtp, oldval, true);
Paul E. McKenneyeb348b82013-06-21 13:00:57 -0700633 rcu_sysidle_exit(rdtp, 1);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100634 local_irq_restore(flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100635}
636
637/**
638 * rcu_nmi_enter - inform RCU of entry to NMI context
639 *
640 * If the CPU was idle with dynamic ticks active, and there is no
641 * irq handler running, this updates rdtp->dynticks_nmi to let the
642 * RCU grace-period handling know that the CPU is active.
643 */
644void rcu_nmi_enter(void)
645{
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700646 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100647
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700648 if (rdtp->dynticks_nmi_nesting == 0 &&
649 (atomic_read(&rdtp->dynticks) & 0x1))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100650 return;
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700651 rdtp->dynticks_nmi_nesting++;
652 smp_mb__before_atomic_inc(); /* Force delay from prior write. */
653 atomic_inc(&rdtp->dynticks);
654 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
655 smp_mb__after_atomic_inc(); /* See above. */
656 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100657}
658
659/**
660 * rcu_nmi_exit - inform RCU of exit from NMI context
661 *
662 * If the CPU was idle with dynamic ticks active, and there is no
663 * irq handler running, this updates rdtp->dynticks_nmi to let the
664 * RCU grace-period handling know that the CPU is no longer active.
665 */
666void rcu_nmi_exit(void)
667{
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700668 struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100669
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700670 if (rdtp->dynticks_nmi_nesting == 0 ||
671 --rdtp->dynticks_nmi_nesting != 0)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100672 return;
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700673 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
674 smp_mb__before_atomic_inc(); /* See above. */
675 atomic_inc(&rdtp->dynticks);
676 smp_mb__after_atomic_inc(); /* Force delay to next write. */
677 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100678}
679
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100680/**
Paul E. McKenneycc6783f2013-09-06 17:39:49 -0700681 * __rcu_is_watching - are RCU read-side critical sections safe?
682 *
683 * Return true if RCU is watching the running CPU, which means that
684 * this CPU can safely enter RCU read-side critical sections. Unlike
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700685 * rcu_is_watching(), the caller of __rcu_is_watching() must have at
Paul E. McKenneycc6783f2013-09-06 17:39:49 -0700686 * least disabled preemption.
687 */
Linus Torvaldsb29c8302013-11-16 12:23:18 -0800688bool notrace __rcu_is_watching(void)
Paul E. McKenneycc6783f2013-09-06 17:39:49 -0700689{
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700690 return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1;
Paul E. McKenneycc6783f2013-09-06 17:39:49 -0700691}
692
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700693/**
694 * rcu_is_watching - see if RCU thinks that the current CPU is idle
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100695 *
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700696 * If the current CPU is in its idle loop and is neither in an interrupt
Paul E. McKenney34240692011-10-03 11:38:52 -0700697 * or NMI handler, return true.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100698 */
Linus Torvaldsb29c8302013-11-16 12:23:18 -0800699bool notrace rcu_is_watching(void)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100700{
Paul E. McKenney34240692011-10-03 11:38:52 -0700701 int ret;
702
703 preempt_disable();
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700704 ret = __rcu_is_watching();
Paul E. McKenney34240692011-10-03 11:38:52 -0700705 preempt_enable();
706 return ret;
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700707}
Paul E. McKenney5c173eb2013-09-13 17:20:11 -0700708EXPORT_SYMBOL_GPL(rcu_is_watching);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700709
Paul E. McKenney62fde6e2012-05-22 22:10:24 -0700710#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU)
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800711
712/*
713 * Is the current CPU online? Disable preemption to avoid false positives
714 * that could otherwise happen due to the current CPU number being sampled,
715 * this task being preempted, its old CPU being taken offline, resuming
716 * on some other CPU, then determining that its old CPU is now offline.
717 * It is OK to use RCU on an offline processor during initial boot, hence
Paul E. McKenney2036d942012-01-30 17:02:47 -0800718 * the check for rcu_scheduler_fully_active. Note also that it is OK
719 * for a CPU coming online to use RCU for one jiffy prior to marking itself
720 * online in the cpu_online_mask. Similarly, it is OK for a CPU going
721 * offline to continue to use RCU for one jiffy after marking itself
722 * offline in the cpu_online_mask. This leniency is necessary given the
723 * non-atomic nature of the online and offline processing, for example,
724 * the fact that a CPU enters the scheduler after completing the CPU_DYING
725 * notifiers.
726 *
727 * This is also why RCU internally marks CPUs online during the
728 * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800729 *
730 * Disable checking if in an NMI handler because we cannot safely report
731 * errors from NMI handlers anyway.
732 */
733bool rcu_lockdep_current_cpu_online(void)
734{
Paul E. McKenney2036d942012-01-30 17:02:47 -0800735 struct rcu_data *rdp;
736 struct rcu_node *rnp;
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800737 bool ret;
738
739 if (in_nmi())
Fengguang Wuf6f7ee92013-10-10 11:08:33 -0700740 return true;
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800741 preempt_disable();
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700742 rdp = this_cpu_ptr(&rcu_sched_data);
Paul E. McKenney2036d942012-01-30 17:02:47 -0800743 rnp = rdp->mynode;
744 ret = (rdp->grpmask & rnp->qsmaskinit) ||
Paul E. McKenneyc0d6d012012-01-23 12:41:26 -0800745 !rcu_scheduler_fully_active;
746 preempt_enable();
747 return ret;
748}
749EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
750
Paul E. McKenney62fde6e2012-05-22 22:10:24 -0700751#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700752
753/**
754 * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
755 *
756 * If the current CPU is idle or running at a first-level (not nested)
757 * interrupt from idle, return true. The caller must have at least
758 * disabled preemption.
759 */
Josh Triplett62e3cb12012-11-20 09:55:26 -0800760static int rcu_is_cpu_rrupt_from_idle(void)
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -0700761{
Christoph Lameterc9d4b0a2013-08-31 13:34:10 -0700762 return __this_cpu_read(rcu_dynticks.dynticks_nesting) <= 1;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100763}
764
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100765/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100766 * Snapshot the specified CPU's dynticks counter so that we can later
767 * credit them with an implicit quiescent state. Return 1 if this CPU
Paul E. McKenney1eba8f82009-09-23 09:50:42 -0700768 * is in dynticks idle mode, which is an extended quiescent state.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100769 */
Paul E. McKenney217af2a2013-06-21 15:39:06 -0700770static int dyntick_save_progress_counter(struct rcu_data *rdp,
771 bool *isidle, unsigned long *maxj)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100772{
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700773 rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
Paul E. McKenney0edd1b12013-06-21 16:37:22 -0700774 rcu_sysidle_check_cpu(rdp, isidle, maxj);
Andreea-Cristina Bernat7941dbd2014-03-17 18:33:28 +0200775 if ((rdp->dynticks_snap & 0x1) == 0) {
776 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
777 return 1;
778 } else {
779 return 0;
780 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100781}
782
783/*
Paul E. McKenney6193c762013-09-23 13:57:18 -0700784 * This function really isn't for public consumption, but RCU is special in
785 * that context switches can allow the state machine to make progress.
786 */
787extern void resched_cpu(int cpu);
788
789/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100790 * Return true if the specified CPU has passed through a quiescent
791 * state by virtue of being in or having passed through an dynticks
792 * idle state since the last call to dyntick_save_progress_counter()
Paul E. McKenneya82dcc72012-08-01 14:29:20 -0700793 * for this same CPU, or by virtue of having been offline.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100794 */
Paul E. McKenney217af2a2013-06-21 15:39:06 -0700795static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
796 bool *isidle, unsigned long *maxj)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100797{
Paul E. McKenney7eb4f452011-07-30 07:32:48 -0700798 unsigned int curr;
799 unsigned int snap;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100800
Paul E. McKenney7eb4f452011-07-30 07:32:48 -0700801 curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
802 snap = (unsigned int)rdp->dynticks_snap;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100803
804 /*
805 * If the CPU passed through or entered a dynticks idle phase with
806 * no active irq/NMI handlers, then we can safely pretend that the CPU
807 * already acknowledged the request to pass through a quiescent
808 * state. Either way, that CPU cannot possibly be in an RCU
809 * read-side critical section that started before the beginning
810 * of the current RCU grace period.
811 */
Paul E. McKenney7eb4f452011-07-30 07:32:48 -0700812 if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400813 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100814 rdp->dynticks_fqs++;
815 return 1;
816 }
817
Paul E. McKenneya82dcc72012-08-01 14:29:20 -0700818 /*
819 * Check for the CPU being offline, but only if the grace period
820 * is old enough. We don't need to worry about the CPU changing
821 * state: If we see it offline even once, it has been through a
822 * quiescent state.
823 *
824 * The reason for insisting that the grace period be at least
825 * one jiffy old is that CPUs that are not quite online and that
826 * have just gone offline can still execute RCU read-side critical
827 * sections.
828 */
829 if (ULONG_CMP_GE(rdp->rsp->gp_start + 2, jiffies))
830 return 0; /* Grace period is not old enough. */
831 barrier();
832 if (cpu_is_offline(rdp->cpu)) {
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -0400833 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("ofl"));
Paul E. McKenneya82dcc72012-08-01 14:29:20 -0700834 rdp->offline_fqs++;
835 return 1;
836 }
Paul E. McKenney65d798f2013-04-12 16:19:10 -0700837
838 /*
839 * There is a possibility that a CPU in adaptive-ticks state
840 * might run in the kernel with the scheduling-clock tick disabled
841 * for an extended time period. Invoke rcu_kick_nohz_cpu() to
842 * force the CPU to restart the scheduling-clock tick in this
843 * CPU is in this state.
844 */
845 rcu_kick_nohz_cpu(rdp->cpu);
846
Paul E. McKenney6193c762013-09-23 13:57:18 -0700847 /*
848 * Alternatively, the CPU might be running in the kernel
849 * for an extended period of time without a quiescent state.
850 * Attempt to force the CPU through the scheduler to gain the
851 * needed quiescent state, but only if the grace period has gone
852 * on for an uncommonly long time. If there are many stuck CPUs,
853 * we will beat on the first one until it gets unstuck, then move
854 * to the next. Only do this for the primary flavor of RCU.
855 */
856 if (rdp->rsp == rcu_state &&
Paul E. McKenneycb1e78c2013-12-04 18:42:03 -0800857 ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) {
Paul E. McKenney6193c762013-09-23 13:57:18 -0700858 rdp->rsp->jiffies_resched += 5;
859 resched_cpu(rdp->cpu);
860 }
861
Paul E. McKenneya82dcc72012-08-01 14:29:20 -0700862 return 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100863}
864
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100865static void record_gp_stall_check_time(struct rcu_state *rsp)
866{
Paul E. McKenneycb1e78c2013-12-04 18:42:03 -0800867 unsigned long j = jiffies;
Paul E. McKenney6193c762013-09-23 13:57:18 -0700868 unsigned long j1;
Paul E. McKenney26cdfed2013-09-04 10:51:13 -0700869
870 rsp->gp_start = j;
871 smp_wmb(); /* Record start time before stall time. */
Paul E. McKenney6193c762013-09-23 13:57:18 -0700872 j1 = rcu_jiffies_till_stall_check();
Iulia Manda4fc5b752014-03-11 15:22:28 +0200873 ACCESS_ONCE(rsp->jiffies_stall) = j + j1;
Paul E. McKenney6193c762013-09-23 13:57:18 -0700874 rsp->jiffies_resched = j + j1 / 2;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100875}
876
Paul E. McKenneyb637a322012-09-19 16:58:38 -0700877/*
878 * Dump stacks of all tasks running on stalled CPUs. This is a fallback
879 * for architectures that do not implement trigger_all_cpu_backtrace().
880 * The NMI-triggered stack traces are more accurate because they are
881 * printed by the target CPU.
882 */
883static void rcu_dump_cpu_stacks(struct rcu_state *rsp)
884{
885 int cpu;
886 unsigned long flags;
887 struct rcu_node *rnp;
888
889 rcu_for_each_leaf_node(rsp, rnp) {
890 raw_spin_lock_irqsave(&rnp->lock, flags);
891 if (rnp->qsmask != 0) {
892 for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
893 if (rnp->qsmask & (1UL << cpu))
894 dump_cpu_task(rnp->grplo + cpu);
895 }
896 raw_spin_unlock_irqrestore(&rnp->lock, flags);
897 }
898}
899
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100900static void print_other_cpu_stall(struct rcu_state *rsp)
901{
902 int cpu;
903 long delta;
904 unsigned long flags;
Paul E. McKenney285fe292012-05-09 08:45:12 -0700905 int ndetected = 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100906 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenney53bb8572012-09-21 16:35:25 -0700907 long totqlen = 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100908
909 /* Only let one CPU complain about others per time interval. */
910
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800911 raw_spin_lock_irqsave(&rnp->lock, flags);
Iulia Manda4fc5b752014-03-11 15:22:28 +0200912 delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700913 if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800914 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100915 return;
916 }
Iulia Manda4fc5b752014-03-11 15:22:28 +0200917 ACCESS_ONCE(rsp->jiffies_stall) = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800918 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100919
Paul E. McKenney8cdd32a2010-08-09 14:23:03 -0700920 /*
921 * OK, time to rat on our buddy...
922 * See Documentation/RCU/stallwarn.txt for info on how to debug
923 * RCU CPU stall warnings.
924 */
Paul E. McKenneyd7f3e202013-03-18 16:19:52 -0700925 pr_err("INFO: %s detected stalls on CPUs/tasks:",
Paul E. McKenney4300aa62010-04-13 16:18:22 -0700926 rsp->name);
Paul E. McKenneya858af22012-01-16 13:29:10 -0800927 print_cpu_stall_info_begin();
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700928 rcu_for_each_leaf_node(rsp, rnp) {
Paul E. McKenney3acd9eb2010-02-22 17:05:03 -0800929 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700930 ndetected += rcu_print_task_stall(rnp);
Paul E. McKenneyc8020a62012-08-10 16:55:59 -0700931 if (rnp->qsmask != 0) {
932 for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
933 if (rnp->qsmask & (1UL << cpu)) {
934 print_cpu_stall_info(rsp,
935 rnp->grplo + cpu);
936 ndetected++;
937 }
938 }
Paul E. McKenney3acd9eb2010-02-22 17:05:03 -0800939 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100940 }
Paul E. McKenneya858af22012-01-16 13:29:10 -0800941
942 /*
943 * Now rat on any tasks that got kicked up to the root rcu_node
944 * due to CPU offlining.
945 */
946 rnp = rcu_get_root(rsp);
947 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney285fe292012-05-09 08:45:12 -0700948 ndetected += rcu_print_task_stall(rnp);
Paul E. McKenneya858af22012-01-16 13:29:10 -0800949 raw_spin_unlock_irqrestore(&rnp->lock, flags);
950
951 print_cpu_stall_info_end();
Paul E. McKenney53bb8572012-09-21 16:35:25 -0700952 for_each_possible_cpu(cpu)
953 totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
Paul E. McKenney83ebe632014-03-06 11:09:10 -0800954 pr_cont("(detected by %d, t=%ld jiffies, g=%ld, c=%ld, q=%lu)\n",
Paul E. McKenneyeee05882012-09-21 14:15:05 -0700955 smp_processor_id(), (long)(jiffies - rsp->gp_start),
Paul E. McKenney83ebe632014-03-06 11:09:10 -0800956 (long)rsp->gpnum, (long)rsp->completed, totqlen);
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700957 if (ndetected == 0)
Paul E. McKenneyd7f3e202013-03-18 16:19:52 -0700958 pr_err("INFO: Stall ended before state dump start\n");
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700959 else if (!trigger_all_cpu_backtrace())
Paul E. McKenneyb637a322012-09-19 16:58:38 -0700960 rcu_dump_cpu_stacks(rsp);
Ingo Molnarc1dc0b92009-08-02 11:28:21 +0200961
Paul E. McKenney4cdfc172012-06-22 17:06:26 -0700962 /* Complain about tasks blocking the grace period. */
Paul E. McKenney1ed509a2010-02-22 17:05:05 -0800963
964 rcu_print_detail_task_stall(rsp);
965
Paul E. McKenney4cdfc172012-06-22 17:06:26 -0700966 force_quiescent_state(rsp); /* Kick them all. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100967}
968
Peter Zijlstrab021fe32013-09-17 09:30:55 +0200969/*
970 * This function really isn't for public consumption, but RCU is special in
971 * that context switches can allow the state machine to make progress.
972 */
973extern void resched_cpu(int cpu);
974
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100975static void print_cpu_stall(struct rcu_state *rsp)
976{
Paul E. McKenney53bb8572012-09-21 16:35:25 -0700977 int cpu;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100978 unsigned long flags;
979 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenney53bb8572012-09-21 16:35:25 -0700980 long totqlen = 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100981
Paul E. McKenney8cdd32a2010-08-09 14:23:03 -0700982 /*
983 * OK, time to rat on ourselves...
984 * See Documentation/RCU/stallwarn.txt for info on how to debug
985 * RCU CPU stall warnings.
986 */
Paul E. McKenneyd7f3e202013-03-18 16:19:52 -0700987 pr_err("INFO: %s self-detected stall on CPU", rsp->name);
Paul E. McKenneya858af22012-01-16 13:29:10 -0800988 print_cpu_stall_info_begin();
989 print_cpu_stall_info(rsp, smp_processor_id());
990 print_cpu_stall_info_end();
Paul E. McKenney53bb8572012-09-21 16:35:25 -0700991 for_each_possible_cpu(cpu)
992 totqlen += per_cpu_ptr(rsp->rda, cpu)->qlen;
Paul E. McKenney83ebe632014-03-06 11:09:10 -0800993 pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n",
994 jiffies - rsp->gp_start,
995 (long)rsp->gpnum, (long)rsp->completed, totqlen);
Paul E. McKenney4627e242011-08-03 03:34:24 -0700996 if (!trigger_all_cpu_backtrace())
997 dump_stack();
Ingo Molnarc1dc0b92009-08-02 11:28:21 +0200998
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800999 raw_spin_lock_irqsave(&rnp->lock, flags);
Iulia Manda4fc5b752014-03-11 15:22:28 +02001000 if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall)))
1001 ACCESS_ONCE(rsp->jiffies_stall) = jiffies +
Paul E. McKenney6bfc09e2012-10-19 12:49:17 -07001002 3 * rcu_jiffies_till_stall_check() + 3;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001003 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Ingo Molnarc1dc0b92009-08-02 11:28:21 +02001004
Peter Zijlstrab021fe32013-09-17 09:30:55 +02001005 /*
1006 * Attempt to revive the RCU machinery by forcing a context switch.
1007 *
1008 * A context switch would normally allow the RCU state machine to make
1009 * progress and it could be we're stuck in kernel space without context
1010 * switches for an entirely unreasonable amount of time.
1011 */
1012 resched_cpu(smp_processor_id());
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001013}
1014
1015static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
1016{
Paul E. McKenney26cdfed2013-09-04 10:51:13 -07001017 unsigned long completed;
1018 unsigned long gpnum;
1019 unsigned long gps;
Paul E. McKenneybad6e132011-05-02 23:40:04 -07001020 unsigned long j;
1021 unsigned long js;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001022 struct rcu_node *rnp;
1023
Paul E. McKenney26cdfed2013-09-04 10:51:13 -07001024 if (rcu_cpu_stall_suppress || !rcu_gp_in_progress(rsp))
Paul E. McKenneyc68de202010-04-15 10:12:40 -07001025 return;
Paul E. McKenneycb1e78c2013-12-04 18:42:03 -08001026 j = jiffies;
Paul E. McKenney26cdfed2013-09-04 10:51:13 -07001027
1028 /*
1029 * Lots of memory barriers to reject false positives.
1030 *
1031 * The idea is to pick up rsp->gpnum, then rsp->jiffies_stall,
1032 * then rsp->gp_start, and finally rsp->completed. These values
1033 * are updated in the opposite order with memory barriers (or
1034 * equivalent) during grace-period initialization and cleanup.
1035 * Now, a false positive can occur if we get an new value of
1036 * rsp->gp_start and a old value of rsp->jiffies_stall. But given
1037 * the memory barriers, the only way that this can happen is if one
1038 * grace period ends and another starts between these two fetches.
1039 * Detect this by comparing rsp->completed with the previous fetch
1040 * from rsp->gpnum.
1041 *
1042 * Given this check, comparisons of jiffies, rsp->jiffies_stall,
1043 * and rsp->gp_start suffice to forestall false positives.
1044 */
1045 gpnum = ACCESS_ONCE(rsp->gpnum);
1046 smp_rmb(); /* Pick up ->gpnum first... */
Paul E. McKenneybad6e132011-05-02 23:40:04 -07001047 js = ACCESS_ONCE(rsp->jiffies_stall);
Paul E. McKenney26cdfed2013-09-04 10:51:13 -07001048 smp_rmb(); /* ...then ->jiffies_stall before the rest... */
1049 gps = ACCESS_ONCE(rsp->gp_start);
1050 smp_rmb(); /* ...and finally ->gp_start before ->completed. */
1051 completed = ACCESS_ONCE(rsp->completed);
1052 if (ULONG_CMP_GE(completed, gpnum) ||
1053 ULONG_CMP_LT(j, js) ||
1054 ULONG_CMP_GE(gps, js))
1055 return; /* No stall or GP completed since entering function. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001056 rnp = rdp->mynode;
Paul E. McKenneyc96ea7c2012-08-13 11:17:06 -07001057 if (rcu_gp_in_progress(rsp) &&
Paul E. McKenney26cdfed2013-09-04 10:51:13 -07001058 (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001059
1060 /* We haven't checked in, so go dump stack. */
1061 print_cpu_stall(rsp);
1062
Paul E. McKenneybad6e132011-05-02 23:40:04 -07001063 } else if (rcu_gp_in_progress(rsp) &&
1064 ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001065
Paul E. McKenneybad6e132011-05-02 23:40:04 -07001066 /* They had a few time units to dump stack, so complain. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001067 print_other_cpu_stall(rsp);
1068 }
1069}
1070
Paul E. McKenney53d84e02010-08-10 14:28:53 -07001071/**
1072 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
1073 *
1074 * Set the stall-warning timeout way off into the future, thus preventing
1075 * any RCU CPU stall-warning messages from appearing in the current set of
1076 * RCU grace periods.
1077 *
1078 * The caller must disable hard irqs.
1079 */
1080void rcu_cpu_stall_reset(void)
1081{
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07001082 struct rcu_state *rsp;
1083
1084 for_each_rcu_flavor(rsp)
Iulia Manda4fc5b752014-03-11 15:22:28 +02001085 ACCESS_ONCE(rsp->jiffies_stall) = jiffies + ULONG_MAX / 2;
Paul E. McKenney53d84e02010-08-10 14:28:53 -07001086}
1087
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001088/*
Paul E. McKenney3f5d3ea2012-05-09 15:39:56 -07001089 * Initialize the specified rcu_data structure's callback list to empty.
1090 */
1091static void init_callback_list(struct rcu_data *rdp)
1092{
1093 int i;
1094
Paul E. McKenney34ed62462013-01-07 13:37:42 -08001095 if (init_nocb_callback_list(rdp))
1096 return;
Paul E. McKenney3f5d3ea2012-05-09 15:39:56 -07001097 rdp->nxtlist = NULL;
1098 for (i = 0; i < RCU_NEXT_SIZE; i++)
1099 rdp->nxttail[i] = &rdp->nxtlist;
1100}
1101
1102/*
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001103 * Determine the value that ->completed will have at the end of the
1104 * next subsequent grace period. This is used to tag callbacks so that
1105 * a CPU can invoke callbacks in a timely fashion even if that CPU has
1106 * been dyntick-idle for an extended period with callbacks under the
1107 * influence of RCU_FAST_NO_HZ.
1108 *
1109 * The caller must hold rnp->lock with interrupts disabled.
1110 */
1111static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
1112 struct rcu_node *rnp)
1113{
1114 /*
1115 * If RCU is idle, we just wait for the next grace period.
1116 * But we can only be sure that RCU is idle if we are looking
1117 * at the root rcu_node structure -- otherwise, a new grace
1118 * period might have started, but just not yet gotten around
1119 * to initializing the current non-root rcu_node structure.
1120 */
1121 if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
1122 return rnp->completed + 1;
1123
1124 /*
1125 * Otherwise, wait for a possible partial grace period and
1126 * then the subsequent full grace period.
1127 */
1128 return rnp->completed + 2;
1129}
1130
1131/*
Paul E. McKenney0446be42012-12-30 15:21:01 -08001132 * Trace-event helper function for rcu_start_future_gp() and
1133 * rcu_nocb_wait_gp().
1134 */
1135static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
Steven Rostedt (Red Hat)e66c33d2013-07-12 16:50:28 -04001136 unsigned long c, const char *s)
Paul E. McKenney0446be42012-12-30 15:21:01 -08001137{
1138 trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
1139 rnp->completed, c, rnp->level,
1140 rnp->grplo, rnp->grphi, s);
1141}
1142
1143/*
1144 * Start some future grace period, as needed to handle newly arrived
1145 * callbacks. The required future grace periods are recorded in each
Paul E. McKenney48a76392014-03-11 13:02:16 -07001146 * rcu_node structure's ->need_future_gp field. Returns true if there
1147 * is reason to awaken the grace-period kthread.
Paul E. McKenney0446be42012-12-30 15:21:01 -08001148 *
1149 * The caller must hold the specified rcu_node structure's ->lock.
1150 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001151static bool __maybe_unused
1152rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
1153 unsigned long *c_out)
Paul E. McKenney0446be42012-12-30 15:21:01 -08001154{
1155 unsigned long c;
1156 int i;
Paul E. McKenney48a76392014-03-11 13:02:16 -07001157 bool ret = false;
Paul E. McKenney0446be42012-12-30 15:21:01 -08001158 struct rcu_node *rnp_root = rcu_get_root(rdp->rsp);
1159
1160 /*
1161 * Pick up grace-period number for new callbacks. If this
1162 * grace period is already marked as needed, return to the caller.
1163 */
1164 c = rcu_cbs_completed(rdp->rsp, rnp);
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001165 trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf"));
Paul E. McKenney0446be42012-12-30 15:21:01 -08001166 if (rnp->need_future_gp[c & 0x1]) {
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001167 trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf"));
Paul E. McKenney48a76392014-03-11 13:02:16 -07001168 goto out;
Paul E. McKenney0446be42012-12-30 15:21:01 -08001169 }
1170
1171 /*
1172 * If either this rcu_node structure or the root rcu_node structure
1173 * believe that a grace period is in progress, then we must wait
1174 * for the one following, which is in "c". Because our request
1175 * will be noticed at the end of the current grace period, we don't
1176 * need to explicitly start one.
1177 */
1178 if (rnp->gpnum != rnp->completed ||
1179 ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) {
1180 rnp->need_future_gp[c & 0x1]++;
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001181 trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf"));
Paul E. McKenney48a76392014-03-11 13:02:16 -07001182 goto out;
Paul E. McKenney0446be42012-12-30 15:21:01 -08001183 }
1184
1185 /*
1186 * There might be no grace period in progress. If we don't already
1187 * hold it, acquire the root rcu_node structure's lock in order to
1188 * start one (if needed).
1189 */
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001190 if (rnp != rnp_root) {
Paul E. McKenney0446be42012-12-30 15:21:01 -08001191 raw_spin_lock(&rnp_root->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001192 smp_mb__after_unlock_lock();
1193 }
Paul E. McKenney0446be42012-12-30 15:21:01 -08001194
1195 /*
1196 * Get a new grace-period number. If there really is no grace
1197 * period in progress, it will be smaller than the one we obtained
1198 * earlier. Adjust callbacks as needed. Note that even no-CBs
1199 * CPUs have a ->nxtcompleted[] array, so no no-CBs checks needed.
1200 */
1201 c = rcu_cbs_completed(rdp->rsp, rnp_root);
1202 for (i = RCU_DONE_TAIL; i < RCU_NEXT_TAIL; i++)
1203 if (ULONG_CMP_LT(c, rdp->nxtcompleted[i]))
1204 rdp->nxtcompleted[i] = c;
1205
1206 /*
1207 * If the needed for the required grace period is already
1208 * recorded, trace and leave.
1209 */
1210 if (rnp_root->need_future_gp[c & 0x1]) {
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001211 trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot"));
Paul E. McKenney0446be42012-12-30 15:21:01 -08001212 goto unlock_out;
1213 }
1214
1215 /* Record the need for the future grace period. */
1216 rnp_root->need_future_gp[c & 0x1]++;
1217
1218 /* If a grace period is not already in progress, start one. */
1219 if (rnp_root->gpnum != rnp_root->completed) {
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001220 trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot"));
Paul E. McKenney0446be42012-12-30 15:21:01 -08001221 } else {
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001222 trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot"));
Paul E. McKenney48a76392014-03-11 13:02:16 -07001223 ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp);
Paul E. McKenney0446be42012-12-30 15:21:01 -08001224 }
1225unlock_out:
1226 if (rnp != rnp_root)
1227 raw_spin_unlock(&rnp_root->lock);
Paul E. McKenney48a76392014-03-11 13:02:16 -07001228out:
1229 if (c_out != NULL)
1230 *c_out = c;
1231 return ret;
Paul E. McKenney0446be42012-12-30 15:21:01 -08001232}
1233
1234/*
1235 * Clean up any old requests for the just-ended grace period. Also return
1236 * whether any additional grace periods have been requested. Also invoke
1237 * rcu_nocb_gp_cleanup() in order to wake up any no-callbacks kthreads
1238 * waiting for this grace period to complete.
1239 */
1240static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
1241{
1242 int c = rnp->completed;
1243 int needmore;
1244 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
1245
1246 rcu_nocb_gp_cleanup(rsp, rnp);
1247 rnp->need_future_gp[c & 0x1] = 0;
1248 needmore = rnp->need_future_gp[(c + 1) & 0x1];
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001249 trace_rcu_future_gp(rnp, rdp, c,
1250 needmore ? TPS("CleanupMore") : TPS("Cleanup"));
Paul E. McKenney0446be42012-12-30 15:21:01 -08001251 return needmore;
1252}
1253
1254/*
Paul E. McKenney48a76392014-03-11 13:02:16 -07001255 * Awaken the grace-period kthread for the specified flavor of RCU.
1256 * Don't do a self-awaken, and don't bother awakening when there is
1257 * nothing for the grace-period kthread to do (as in several CPUs
1258 * raced to awaken, and we lost), and finally don't try to awaken
1259 * a kthread that has not yet been created.
1260 */
1261static void rcu_gp_kthread_wake(struct rcu_state *rsp)
1262{
1263 if (current == rsp->gp_kthread ||
1264 !ACCESS_ONCE(rsp->gp_flags) ||
1265 !rsp->gp_kthread)
1266 return;
1267 wake_up(&rsp->gp_wq);
1268}
1269
1270/*
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001271 * If there is room, assign a ->completed number to any callbacks on
1272 * this CPU that have not already been assigned. Also accelerate any
1273 * callbacks that were previously assigned a ->completed number that has
1274 * since proven to be too conservative, which can happen if callbacks get
1275 * assigned a ->completed number while RCU is idle, but with reference to
1276 * a non-root rcu_node structure. This function is idempotent, so it does
Paul E. McKenney48a76392014-03-11 13:02:16 -07001277 * not hurt to call it repeatedly. Returns an flag saying that we should
1278 * awaken the RCU grace-period kthread.
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001279 *
1280 * The caller must hold rnp->lock with interrupts disabled.
1281 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001282static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001283 struct rcu_data *rdp)
1284{
1285 unsigned long c;
1286 int i;
Paul E. McKenney48a76392014-03-11 13:02:16 -07001287 bool ret;
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001288
1289 /* If the CPU has no callbacks, nothing to do. */
1290 if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
Paul E. McKenney48a76392014-03-11 13:02:16 -07001291 return false;
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001292
1293 /*
1294 * Starting from the sublist containing the callbacks most
1295 * recently assigned a ->completed number and working down, find the
1296 * first sublist that is not assignable to an upcoming grace period.
1297 * Such a sublist has something in it (first two tests) and has
1298 * a ->completed number assigned that will complete sooner than
1299 * the ->completed number for newly arrived callbacks (last test).
1300 *
1301 * The key point is that any later sublist can be assigned the
1302 * same ->completed number as the newly arrived callbacks, which
1303 * means that the callbacks in any of these later sublist can be
1304 * grouped into a single sublist, whether or not they have already
1305 * been assigned a ->completed number.
1306 */
1307 c = rcu_cbs_completed(rsp, rnp);
1308 for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--)
1309 if (rdp->nxttail[i] != rdp->nxttail[i - 1] &&
1310 !ULONG_CMP_GE(rdp->nxtcompleted[i], c))
1311 break;
1312
1313 /*
1314 * If there are no sublist for unassigned callbacks, leave.
1315 * At the same time, advance "i" one sublist, so that "i" will
1316 * index into the sublist where all the remaining callbacks should
1317 * be grouped into.
1318 */
1319 if (++i >= RCU_NEXT_TAIL)
Paul E. McKenney48a76392014-03-11 13:02:16 -07001320 return false;
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001321
1322 /*
1323 * Assign all subsequent callbacks' ->completed number to the next
1324 * full grace period and group them all in the sublist initially
1325 * indexed by "i".
1326 */
1327 for (; i <= RCU_NEXT_TAIL; i++) {
1328 rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
1329 rdp->nxtcompleted[i] = c;
1330 }
Paul E. McKenney910ee452012-12-31 02:24:21 -08001331 /* Record any needed additional grace periods. */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001332 ret = rcu_start_future_gp(rnp, rdp, NULL);
Paul E. McKenney6d4b4182012-11-27 16:55:44 -08001333
1334 /* Trace depending on how much we were able to accelerate. */
1335 if (!*rdp->nxttail[RCU_WAIT_TAIL])
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001336 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccWaitCB"));
Paul E. McKenney6d4b4182012-11-27 16:55:44 -08001337 else
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001338 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("AccReadyCB"));
Paul E. McKenney48a76392014-03-11 13:02:16 -07001339 return ret;
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001340}
1341
1342/*
1343 * Move any callbacks whose grace period has completed to the
1344 * RCU_DONE_TAIL sublist, then compact the remaining sublists and
1345 * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
1346 * sublist. This function is idempotent, so it does not hurt to
1347 * invoke it repeatedly. As long as it is not invoked -too- often...
Paul E. McKenney48a76392014-03-11 13:02:16 -07001348 * Returns true if the RCU grace-period kthread needs to be awakened.
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001349 *
1350 * The caller must hold rnp->lock with interrupts disabled.
1351 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001352static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001353 struct rcu_data *rdp)
1354{
1355 int i, j;
1356
1357 /* If the CPU has no callbacks, nothing to do. */
1358 if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
Paul E. McKenney48a76392014-03-11 13:02:16 -07001359 return false;
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001360
1361 /*
1362 * Find all callbacks whose ->completed numbers indicate that they
1363 * are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
1364 */
1365 for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
1366 if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i]))
1367 break;
1368 rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i];
1369 }
1370 /* Clean up any sublist tail pointers that were misordered above. */
1371 for (j = RCU_WAIT_TAIL; j < i; j++)
1372 rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL];
1373
1374 /* Copy down callbacks to fill in empty sublists. */
1375 for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
1376 if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL])
1377 break;
1378 rdp->nxttail[j] = rdp->nxttail[i];
1379 rdp->nxtcompleted[j] = rdp->nxtcompleted[i];
1380 }
1381
1382 /* Classify any remaining callbacks. */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001383 return rcu_accelerate_cbs(rsp, rnp, rdp);
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001384}
1385
1386/*
Paul E. McKenneyba9fbe92013-03-19 11:53:31 -07001387 * Update CPU-local rcu_data state to record the beginnings and ends of
1388 * grace periods. The caller must hold the ->lock of the leaf rcu_node
1389 * structure corresponding to the current CPU, and must have irqs disabled.
Paul E. McKenney48a76392014-03-11 13:02:16 -07001390 * Returns true if the grace-period kthread needs to be awakened.
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001391 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001392static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
1393 struct rcu_data *rdp)
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001394{
Paul E. McKenney48a76392014-03-11 13:02:16 -07001395 bool ret;
1396
Paul E. McKenneyba9fbe92013-03-19 11:53:31 -07001397 /* Handle the ends of any preceding grace periods first. */
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001398 if (rdp->completed == rnp->completed) {
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001399
Paul E. McKenneyba9fbe92013-03-19 11:53:31 -07001400 /* No grace period end, so just accelerate recent callbacks. */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001401 ret = rcu_accelerate_cbs(rsp, rnp, rdp);
Paul E. McKenneydc35c892012-12-03 13:52:00 -08001402
1403 } else {
1404
1405 /* Advance callbacks. */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001406 ret = rcu_advance_cbs(rsp, rnp, rdp);
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001407
1408 /* Remember that we saw this grace-period completion. */
1409 rdp->completed = rnp->completed;
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001410 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuend"));
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001411 }
Paul E. McKenney398ebe62013-03-19 10:53:14 -07001412
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001413 if (rdp->gpnum != rnp->gpnum) {
1414 /*
1415 * If the current grace period is waiting for this CPU,
1416 * set up to detect a quiescent state, otherwise don't
1417 * go looking for one.
1418 */
1419 rdp->gpnum = rnp->gpnum;
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001420 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpustart"));
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001421 rdp->passed_quiesce = 0;
1422 rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
1423 zero_cpu_stall_ticks(rdp);
1424 }
Paul E. McKenney48a76392014-03-11 13:02:16 -07001425 return ret;
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001426}
1427
Paul E. McKenneyd34ea322013-03-19 11:10:43 -07001428static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001429{
1430 unsigned long flags;
Paul E. McKenney48a76392014-03-11 13:02:16 -07001431 bool needwake;
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001432 struct rcu_node *rnp;
1433
1434 local_irq_save(flags);
1435 rnp = rdp->mynode;
Paul E. McKenneyd34ea322013-03-19 11:10:43 -07001436 if ((rdp->gpnum == ACCESS_ONCE(rnp->gpnum) &&
1437 rdp->completed == ACCESS_ONCE(rnp->completed)) || /* w/out lock. */
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001438 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
1439 local_irq_restore(flags);
1440 return;
1441 }
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001442 smp_mb__after_unlock_lock();
Paul E. McKenney48a76392014-03-11 13:02:16 -07001443 needwake = __note_gp_changes(rsp, rnp, rdp);
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001444 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney48a76392014-03-11 13:02:16 -07001445 if (needwake)
1446 rcu_gp_kthread_wake(rsp);
Paul E. McKenney6eaef632013-03-19 10:08:37 -07001447}
1448
1449/*
Paul E. McKenneyf7be8202013-08-08 18:27:52 -07001450 * Initialize a new grace period. Return 0 if no grace period required.
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001451 */
1452static int rcu_gp_init(struct rcu_state *rsp)
1453{
1454 struct rcu_data *rdp;
1455 struct rcu_node *rnp = rcu_get_root(rsp);
1456
Paul E. McKenneyeb757672013-06-21 17:10:40 -07001457 rcu_bind_gp_kthread();
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001458 raw_spin_lock_irq(&rnp->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001459 smp_mb__after_unlock_lock();
Paul E. McKenney91dc9542014-02-18 09:47:13 -08001460 if (!ACCESS_ONCE(rsp->gp_flags)) {
Paul E. McKenneyf7be8202013-08-08 18:27:52 -07001461 /* Spurious wakeup, tell caller to go back to sleep. */
1462 raw_spin_unlock_irq(&rnp->lock);
1463 return 0;
1464 }
Paul E. McKenney91dc9542014-02-18 09:47:13 -08001465 ACCESS_ONCE(rsp->gp_flags) = 0; /* Clear all flags: New grace period. */
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001466
Paul E. McKenneyf7be8202013-08-08 18:27:52 -07001467 if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
1468 /*
1469 * Grace period already in progress, don't start another.
1470 * Not supposed to be able to happen.
1471 */
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001472 raw_spin_unlock_irq(&rnp->lock);
1473 return 0;
1474 }
1475
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001476 /* Advance to a new grace period and initialize state. */
Paul E. McKenney26cdfed2013-09-04 10:51:13 -07001477 record_gp_stall_check_time(rsp);
Paul E. McKenney765a3f42014-03-14 16:37:08 -07001478 /* Record GP times before starting GP, hence smp_store_release(). */
1479 smp_store_release(&rsp->gpnum, rsp->gpnum + 1);
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001480 trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start"));
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001481 raw_spin_unlock_irq(&rnp->lock);
1482
1483 /* Exclude any concurrent CPU-hotplug operations. */
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07001484 mutex_lock(&rsp->onoff_mutex);
Paul E. McKenney765a3f42014-03-14 16:37:08 -07001485 smp_mb__after_unlock_lock(); /* ->gpnum increment before GP! */
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001486
1487 /*
1488 * Set the quiescent-state-needed bits in all the rcu_node
1489 * structures for all currently online CPUs in breadth-first order,
1490 * starting from the root rcu_node structure, relying on the layout
1491 * of the tree within the rsp->node[] array. Note that other CPUs
1492 * will access only the leaves of the hierarchy, thus seeing that no
1493 * grace period is in progress, at least until the corresponding
1494 * leaf node has been initialized. In addition, we have excluded
1495 * CPU-hotplug operations.
1496 *
1497 * The grace period cannot complete until the initialization
1498 * process finishes, because this kthread handles both.
1499 */
1500 rcu_for_each_node_breadth_first(rsp, rnp) {
1501 raw_spin_lock_irq(&rnp->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001502 smp_mb__after_unlock_lock();
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001503 rdp = this_cpu_ptr(rsp->rda);
1504 rcu_preempt_check_blocked_tasks(rnp);
1505 rnp->qsmask = rnp->qsmaskinit;
Paul E. McKenney0446be42012-12-30 15:21:01 -08001506 ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
Paul E. McKenney25d30cf2012-07-11 05:23:18 -07001507 WARN_ON_ONCE(rnp->completed != rsp->completed);
Paul E. McKenney0446be42012-12-30 15:21:01 -08001508 ACCESS_ONCE(rnp->completed) = rsp->completed;
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001509 if (rnp == rdp->mynode)
Paul E. McKenney48a76392014-03-11 13:02:16 -07001510 (void)__note_gp_changes(rsp, rnp, rdp);
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001511 rcu_preempt_boost_start_gp(rnp);
1512 trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
1513 rnp->level, rnp->grplo,
1514 rnp->grphi, rnp->qsmask);
1515 raw_spin_unlock_irq(&rnp->lock);
Paul E. McKenney661a85d2012-07-07 05:57:03 -07001516#ifdef CONFIG_PROVE_RCU_DELAY
Paul E. McKenney971394f2013-06-02 07:13:57 -07001517 if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 &&
Paul E. McKenney81e59492013-03-10 15:44:52 -07001518 system_state == SYSTEM_RUNNING)
Paul E. McKenney971394f2013-06-02 07:13:57 -07001519 udelay(200);
Paul E. McKenney661a85d2012-07-07 05:57:03 -07001520#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001521 cond_resched();
1522 }
1523
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07001524 mutex_unlock(&rsp->onoff_mutex);
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001525 return 1;
1526}
1527
1528/*
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001529 * Do one round of quiescent-state forcing.
1530 */
Paul E. McKenney01896f72013-08-18 12:14:32 -07001531static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001532{
1533 int fqs_state = fqs_state_in;
Paul E. McKenney217af2a2013-06-21 15:39:06 -07001534 bool isidle = false;
1535 unsigned long maxj;
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001536 struct rcu_node *rnp = rcu_get_root(rsp);
1537
1538 rsp->n_force_qs++;
1539 if (fqs_state == RCU_SAVE_DYNTICK) {
1540 /* Collect dyntick-idle snapshots. */
Paul E. McKenney0edd1b12013-06-21 16:37:22 -07001541 if (is_sysidle_rcu_state(rsp)) {
1542 isidle = 1;
1543 maxj = jiffies - ULONG_MAX / 4;
1544 }
Paul E. McKenney217af2a2013-06-21 15:39:06 -07001545 force_qs_rnp(rsp, dyntick_save_progress_counter,
1546 &isidle, &maxj);
Paul E. McKenney0edd1b12013-06-21 16:37:22 -07001547 rcu_sysidle_report_gp(rsp, isidle, maxj);
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001548 fqs_state = RCU_FORCE_QS;
1549 } else {
1550 /* Handle dyntick-idle and offline CPUs. */
Paul E. McKenney0edd1b12013-06-21 16:37:22 -07001551 isidle = 0;
Paul E. McKenney217af2a2013-06-21 15:39:06 -07001552 force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj);
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001553 }
1554 /* Clear flag to prevent immediate re-entry. */
1555 if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
1556 raw_spin_lock_irq(&rnp->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001557 smp_mb__after_unlock_lock();
Paul E. McKenney91dc9542014-02-18 09:47:13 -08001558 ACCESS_ONCE(rsp->gp_flags) &= ~RCU_GP_FLAG_FQS;
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001559 raw_spin_unlock_irq(&rnp->lock);
1560 }
1561 return fqs_state;
1562}
1563
1564/*
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001565 * Clean up after the old grace period.
1566 */
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001567static void rcu_gp_cleanup(struct rcu_state *rsp)
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001568{
1569 unsigned long gp_duration;
Paul E. McKenney48a76392014-03-11 13:02:16 -07001570 bool needgp = false;
Paul E. McKenneydae6e642013-02-10 20:48:58 -08001571 int nocb = 0;
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001572 struct rcu_data *rdp;
1573 struct rcu_node *rnp = rcu_get_root(rsp);
1574
1575 raw_spin_lock_irq(&rnp->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001576 smp_mb__after_unlock_lock();
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001577 gp_duration = jiffies - rsp->gp_start;
1578 if (gp_duration > rsp->gp_max)
1579 rsp->gp_max = gp_duration;
1580
1581 /*
1582 * We know the grace period is complete, but to everyone else
1583 * it appears to still be ongoing. But it is also the case
1584 * that to everyone else it looks like there is nothing that
1585 * they can do to advance the grace period. It is therefore
1586 * safe for us to drop the lock in order to mark the grace
1587 * period as completed in all of the rcu_node structures.
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001588 */
Paul E. McKenney5d4b8652012-07-07 07:56:57 -07001589 raw_spin_unlock_irq(&rnp->lock);
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001590
Paul E. McKenney5d4b8652012-07-07 07:56:57 -07001591 /*
1592 * Propagate new ->completed value to rcu_node structures so
1593 * that other CPUs don't have to wait until the start of the next
1594 * grace period to process their callbacks. This also avoids
1595 * some nasty RCU grace-period initialization races by forcing
1596 * the end of the current grace period to be completely recorded in
1597 * all of the rcu_node structures before the beginning of the next
1598 * grace period is recorded in any of the rcu_node structures.
1599 */
1600 rcu_for_each_node_breadth_first(rsp, rnp) {
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001601 raw_spin_lock_irq(&rnp->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001602 smp_mb__after_unlock_lock();
Paul E. McKenney0446be42012-12-30 15:21:01 -08001603 ACCESS_ONCE(rnp->completed) = rsp->gpnum;
Paul E. McKenneyb11cc572012-12-17 14:21:14 -08001604 rdp = this_cpu_ptr(rsp->rda);
1605 if (rnp == rdp->mynode)
Paul E. McKenney48a76392014-03-11 13:02:16 -07001606 needgp = __note_gp_changes(rsp, rnp, rdp) || needgp;
Paul E. McKenney78e4bc32013-09-24 15:04:06 -07001607 /* smp_mb() provided by prior unlock-lock pair. */
Paul E. McKenney0446be42012-12-30 15:21:01 -08001608 nocb += rcu_future_gp_cleanup(rsp, rnp);
Paul E. McKenney5d4b8652012-07-07 07:56:57 -07001609 raw_spin_unlock_irq(&rnp->lock);
1610 cond_resched();
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001611 }
Paul E. McKenney5d4b8652012-07-07 07:56:57 -07001612 rnp = rcu_get_root(rsp);
1613 raw_spin_lock_irq(&rnp->lock);
Paul E. McKenney765a3f42014-03-14 16:37:08 -07001614 smp_mb__after_unlock_lock(); /* Order GP before ->completed update. */
Paul E. McKenneydae6e642013-02-10 20:48:58 -08001615 rcu_nocb_gp_set(rnp, nocb);
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001616
Paul E. McKenney765a3f42014-03-14 16:37:08 -07001617 /* Declare grace period done. */
1618 ACCESS_ONCE(rsp->completed) = rsp->gpnum;
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04001619 trace_rcu_grace_period(rsp->name, rsp->completed, TPS("end"));
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001620 rsp->fqs_state = RCU_GP_IDLE;
Paul E. McKenney5d4b8652012-07-07 07:56:57 -07001621 rdp = this_cpu_ptr(rsp->rda);
Paul E. McKenney48a76392014-03-11 13:02:16 -07001622 /* Advance CBs to reduce false positives below. */
1623 needgp = rcu_advance_cbs(rsp, rnp, rdp) || needgp;
1624 if (needgp || cpu_needs_another_gp(rsp, rdp)) {
Paul E. McKenney91dc9542014-02-18 09:47:13 -08001625 ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT;
Paul E. McKenneybb311ec2013-08-09 16:02:09 -07001626 trace_rcu_grace_period(rsp->name,
1627 ACCESS_ONCE(rsp->gpnum),
1628 TPS("newreq"));
1629 }
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001630 raw_spin_unlock_irq(&rnp->lock);
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001631}
1632
1633/*
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001634 * Body of kthread that handles grace periods.
1635 */
Paul E. McKenney755609a2012-06-19 17:18:20 -07001636static int __noreturn rcu_gp_kthread(void *arg)
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001637{
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001638 int fqs_state;
Paul E. McKenney88d6df62013-08-08 21:44:31 -07001639 int gf;
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07001640 unsigned long j;
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001641 int ret;
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001642 struct rcu_state *rsp = arg;
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001643 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001644
1645 for (;;) {
1646
1647 /* Handle grace-period start. */
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001648 for (;;) {
Paul E. McKenney63c4db72013-08-09 12:19:29 -07001649 trace_rcu_grace_period(rsp->name,
1650 ACCESS_ONCE(rsp->gpnum),
1651 TPS("reqwait"));
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001652 wait_event_interruptible(rsp->gp_wq,
Paul E. McKenney591c6d12013-08-08 22:26:23 -07001653 ACCESS_ONCE(rsp->gp_flags) &
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001654 RCU_GP_FLAG_INIT);
Paul E. McKenney78e4bc32013-09-24 15:04:06 -07001655 /* Locking provides needed memory barrier. */
Paul E. McKenneyf7be8202013-08-08 18:27:52 -07001656 if (rcu_gp_init(rsp))
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001657 break;
Paul E. McKenney7fdefc12012-06-22 11:08:41 -07001658 cond_resched();
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001659 flush_signals(current);
Paul E. McKenney63c4db72013-08-09 12:19:29 -07001660 trace_rcu_grace_period(rsp->name,
1661 ACCESS_ONCE(rsp->gpnum),
1662 TPS("reqwaitsig"));
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001663 }
Paul E. McKenneycabc49c12012-06-20 17:07:14 -07001664
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001665 /* Handle quiescent-state forcing. */
1666 fqs_state = RCU_SAVE_DYNTICK;
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07001667 j = jiffies_till_first_fqs;
1668 if (j > HZ) {
1669 j = HZ;
1670 jiffies_till_first_fqs = HZ;
1671 }
Paul E. McKenney88d6df62013-08-08 21:44:31 -07001672 ret = 0;
Paul E. McKenneycabc49c12012-06-20 17:07:14 -07001673 for (;;) {
Paul E. McKenney88d6df62013-08-08 21:44:31 -07001674 if (!ret)
1675 rsp->jiffies_force_qs = jiffies + j;
Paul E. McKenney63c4db72013-08-09 12:19:29 -07001676 trace_rcu_grace_period(rsp->name,
1677 ACCESS_ONCE(rsp->gpnum),
1678 TPS("fqswait"));
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001679 ret = wait_event_interruptible_timeout(rsp->gp_wq,
Paul E. McKenney88d6df62013-08-08 21:44:31 -07001680 ((gf = ACCESS_ONCE(rsp->gp_flags)) &
1681 RCU_GP_FLAG_FQS) ||
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001682 (!ACCESS_ONCE(rnp->qsmask) &&
1683 !rcu_preempt_blocked_readers_cgp(rnp)),
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07001684 j);
Paul E. McKenney78e4bc32013-09-24 15:04:06 -07001685 /* Locking provides needed memory barriers. */
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001686 /* If grace period done, leave loop. */
Paul E. McKenneycabc49c12012-06-20 17:07:14 -07001687 if (!ACCESS_ONCE(rnp->qsmask) &&
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001688 !rcu_preempt_blocked_readers_cgp(rnp))
Paul E. McKenneycabc49c12012-06-20 17:07:14 -07001689 break;
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001690 /* If time for quiescent-state forcing, do it. */
Paul E. McKenney88d6df62013-08-08 21:44:31 -07001691 if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) ||
1692 (gf & RCU_GP_FLAG_FQS)) {
Paul E. McKenney63c4db72013-08-09 12:19:29 -07001693 trace_rcu_grace_period(rsp->name,
1694 ACCESS_ONCE(rsp->gpnum),
1695 TPS("fqsstart"));
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001696 fqs_state = rcu_gp_fqs(rsp, fqs_state);
Paul E. McKenney63c4db72013-08-09 12:19:29 -07001697 trace_rcu_grace_period(rsp->name,
1698 ACCESS_ONCE(rsp->gpnum),
1699 TPS("fqsend"));
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001700 cond_resched();
1701 } else {
1702 /* Deal with stray signal. */
1703 cond_resched();
1704 flush_signals(current);
Paul E. McKenney63c4db72013-08-09 12:19:29 -07001705 trace_rcu_grace_period(rsp->name,
1706 ACCESS_ONCE(rsp->gpnum),
1707 TPS("fqswaitsig"));
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001708 }
Paul E. McKenneyd40011f2012-06-26 20:45:57 -07001709 j = jiffies_till_next_fqs;
1710 if (j > HZ) {
1711 j = HZ;
1712 jiffies_till_next_fqs = HZ;
1713 } else if (j < 1) {
1714 j = 1;
1715 jiffies_till_next_fqs = 1;
1716 }
Paul E. McKenneycabc49c12012-06-20 17:07:14 -07001717 }
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07001718
1719 /* Handle grace-period end. */
1720 rcu_gp_cleanup(rsp);
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001721 }
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001722}
1723
1724/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001725 * Start a new RCU grace period if warranted, re-initializing the hierarchy
1726 * in preparation for detecting the next grace period. The caller must hold
Paul E. McKenneyb8462082012-12-29 22:04:18 -08001727 * the root node's ->lock and hard irqs must be disabled.
Paul E. McKenneye5601402012-01-07 11:03:57 -08001728 *
1729 * Note that it is legal for a dying CPU (which is marked as offline) to
1730 * invoke this function. This can happen when the dying CPU reports its
1731 * quiescent state.
Paul E. McKenney48a76392014-03-11 13:02:16 -07001732 *
1733 * Returns true if the grace-period kthread must be awakened.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001734 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001735static bool
Paul E. McKenney910ee452012-12-31 02:24:21 -08001736rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
1737 struct rcu_data *rdp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001738{
Paul E. McKenneyb8462082012-12-29 22:04:18 -08001739 if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) {
Paul E. McKenneyb32e9eb2009-11-12 22:35:03 -08001740 /*
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001741 * Either we have not yet spawned the grace-period
Paul E. McKenney62da1922012-09-20 16:02:49 -07001742 * task, this CPU does not need another grace period,
1743 * or a grace period is already in progress.
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07001744 * Either way, don't start a new grace period.
Paul E. McKenneyb32e9eb2009-11-12 22:35:03 -08001745 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001746 return false;
Paul E. McKenneyafe24b12011-08-24 16:52:09 -07001747 }
Paul E. McKenney91dc9542014-02-18 09:47:13 -08001748 ACCESS_ONCE(rsp->gp_flags) = RCU_GP_FLAG_INIT;
Paul E. McKenneybb311ec2013-08-09 16:02:09 -07001749 trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum),
1750 TPS("newreq"));
Paul E. McKenney62da1922012-09-20 16:02:49 -07001751
Steven Rostedt016a8d52013-05-28 17:32:53 -04001752 /*
1753 * We can't do wakeups while holding the rnp->lock, as that
Paul E. McKenney1eafd312013-06-20 13:50:40 -07001754 * could cause possible deadlocks with the rq->lock. Defer
Paul E. McKenney48a76392014-03-11 13:02:16 -07001755 * the wakeup to our caller.
Steven Rostedt016a8d52013-05-28 17:32:53 -04001756 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001757 return true;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001758}
1759
1760/*
Paul E. McKenney910ee452012-12-31 02:24:21 -08001761 * Similar to rcu_start_gp_advanced(), but also advance the calling CPU's
1762 * callbacks. Note that rcu_start_gp_advanced() cannot do this because it
1763 * is invoked indirectly from rcu_advance_cbs(), which would result in
1764 * endless recursion -- or would do so if it wasn't for the self-deadlock
1765 * that is encountered beforehand.
Paul E. McKenney48a76392014-03-11 13:02:16 -07001766 *
1767 * Returns true if the grace-period kthread needs to be awakened.
Paul E. McKenney910ee452012-12-31 02:24:21 -08001768 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001769static bool rcu_start_gp(struct rcu_state *rsp)
Paul E. McKenney910ee452012-12-31 02:24:21 -08001770{
1771 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
1772 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenney48a76392014-03-11 13:02:16 -07001773 bool ret = false;
Paul E. McKenney910ee452012-12-31 02:24:21 -08001774
1775 /*
1776 * If there is no grace period in progress right now, any
1777 * callbacks we have up to this point will be satisfied by the
1778 * next grace period. Also, advancing the callbacks reduces the
1779 * probability of false positives from cpu_needs_another_gp()
1780 * resulting in pointless grace periods. So, advance callbacks
1781 * then start the grace period!
1782 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001783 ret = rcu_advance_cbs(rsp, rnp, rdp) || ret;
1784 ret = rcu_start_gp_advanced(rsp, rnp, rdp) || ret;
1785 return ret;
Paul E. McKenney910ee452012-12-31 02:24:21 -08001786}
1787
1788/*
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001789 * Report a full set of quiescent states to the specified rcu_state
1790 * data structure. This involves cleaning up after the prior grace
1791 * period and letting rcu_start_gp() start up the next grace period
Paul E. McKenneyb8462082012-12-29 22:04:18 -08001792 * if one is needed. Note that the caller must hold rnp->lock, which
1793 * is released before return.
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001794 */
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001795static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -07001796 __releases(rcu_get_root(rsp)->lock)
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001797{
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -07001798 WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
Paul E. McKenneycabc49c12012-06-20 17:07:14 -07001799 raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
1800 wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001801}
1802
1803/*
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001804 * Similar to rcu_report_qs_rdp(), for which it is a helper function.
1805 * Allows quiescent states for a group of CPUs to be reported at one go
1806 * to the specified rcu_node structure, though all the CPUs in the group
1807 * must be represented by the same rcu_node structure (which need not be
1808 * a leaf rcu_node structure, though it often will be). That structure's
1809 * lock must be held upon entry, and it is released before return.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001810 */
1811static void
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001812rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
1813 struct rcu_node *rnp, unsigned long flags)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001814 __releases(rnp->lock)
1815{
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001816 struct rcu_node *rnp_c;
1817
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001818 /* Walk up the rcu_node hierarchy. */
1819 for (;;) {
1820 if (!(rnp->qsmask & mask)) {
1821
1822 /* Our bit has already been cleared, so done. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001823 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001824 return;
1825 }
1826 rnp->qsmask &= ~mask;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001827 trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
1828 mask, rnp->qsmask, rnp->level,
1829 rnp->grplo, rnp->grphi,
1830 !!rnp->gp_tasks);
Paul E. McKenney27f4d282011-02-07 12:47:15 -08001831 if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001832
1833 /* Other bits still set at this level, so done. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001834 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001835 return;
1836 }
1837 mask = rnp->grpmask;
1838 if (rnp->parent == NULL) {
1839
1840 /* No more levels. Exit loop holding root lock. */
1841
1842 break;
1843 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001844 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001845 rnp_c = rnp;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001846 rnp = rnp->parent;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001847 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001848 smp_mb__after_unlock_lock();
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001849 WARN_ON_ONCE(rnp_c->qsmask);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001850 }
1851
1852 /*
1853 * Get here if we are the last CPU to pass through a quiescent
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001854 * state for this grace period. Invoke rcu_report_qs_rsp()
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001855 * to clean up and start the next grace period if one is needed.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001856 */
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001857 rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001858}
1859
1860/*
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001861 * Record a quiescent state for the specified CPU to that CPU's rcu_data
1862 * structure. This must be either called from the specified CPU, or
1863 * called when the specified CPU is known to be offline (and when it is
1864 * also known that no other CPU is concurrently trying to help the offline
1865 * CPU). The lastcomp argument is used to make sure we are still in the
1866 * grace period of interest. We don't want to end the current grace period
1867 * based on quiescent states detected in an earlier grace period!
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001868 */
1869static void
Paul E. McKenneyd7d6a112012-08-21 15:00:05 -07001870rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001871{
1872 unsigned long flags;
1873 unsigned long mask;
Paul E. McKenney48a76392014-03-11 13:02:16 -07001874 bool needwake;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001875 struct rcu_node *rnp;
1876
1877 rnp = rdp->mynode;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001878 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08001879 smp_mb__after_unlock_lock();
Paul E. McKenneyd7d6a112012-08-21 15:00:05 -07001880 if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
1881 rnp->completed == rnp->gpnum) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001882
1883 /*
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001884 * The grace period in which this quiescent state was
1885 * recorded has ended, so don't report it upwards.
1886 * We will instead need a new quiescent state that lies
1887 * within the current grace period.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001888 */
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001889 rdp->passed_quiesce = 0; /* need qs for new gp. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001890 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001891 return;
1892 }
1893 mask = rdp->grpmask;
1894 if ((rnp->qsmask & mask) == 0) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001895 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001896 } else {
1897 rdp->qs_pending = 0;
1898
1899 /*
1900 * This GP can't end until cpu checks in, so all of our
1901 * callbacks can be processed during the next GP.
1902 */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001903 needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001904
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001905 rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
Paul E. McKenney48a76392014-03-11 13:02:16 -07001906 if (needwake)
1907 rcu_gp_kthread_wake(rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001908 }
1909}
1910
1911/*
1912 * Check to see if there is a new grace period of which this CPU
1913 * is not yet aware, and if so, set up local rcu_data state for it.
1914 * Otherwise, see if this CPU has just passed through its first
1915 * quiescent state for this grace period, and record that fact if so.
1916 */
1917static void
1918rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
1919{
Paul E. McKenney05eb5522013-03-19 12:38:24 -07001920 /* Check for grace-period ends and beginnings. */
1921 note_gp_changes(rsp, rdp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001922
1923 /*
1924 * Does this CPU still need to do its part for current grace period?
1925 * If no, return and let the other CPUs do their part as well.
1926 */
1927 if (!rdp->qs_pending)
1928 return;
1929
1930 /*
1931 * Was there a quiescent state since the beginning of the grace
1932 * period? If no, then exit and wait for the next call.
1933 */
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001934 if (!rdp->passed_quiesce)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001935 return;
1936
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001937 /*
1938 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
1939 * judge of that).
1940 */
Paul E. McKenneyd7d6a112012-08-21 15:00:05 -07001941 rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001942}
1943
1944#ifdef CONFIG_HOTPLUG_CPU
1945
1946/*
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001947 * Send the specified CPU's RCU callbacks to the orphanage. The
1948 * specified CPU must be offline, and the caller must hold the
Paul E. McKenney7b2e6012012-10-08 10:54:03 -07001949 * ->orphan_lock.
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001950 */
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001951static void
1952rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
1953 struct rcu_node *rnp, struct rcu_data *rdp)
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001954{
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07001955 /* No-CBs CPUs do not have orphanable callbacks. */
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01001956 if (rcu_is_nocb_cpu(rdp->cpu))
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07001957 return;
1958
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001959 /*
1960 * Orphan the callbacks. First adjust the counts. This is safe
Paul E. McKenneyabfd6e52012-09-20 16:59:47 -07001961 * because _rcu_barrier() excludes CPU-hotplug operations, so it
1962 * cannot be running now. Thus no memory barrier is required.
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001963 */
Paul E. McKenneya50c3af2012-01-10 17:52:31 -08001964 if (rdp->nxtlist != NULL) {
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001965 rsp->qlen_lazy += rdp->qlen_lazy;
1966 rsp->qlen += rdp->qlen;
1967 rdp->n_cbs_orphaned += rdp->qlen;
Paul E. McKenneya50c3af2012-01-10 17:52:31 -08001968 rdp->qlen_lazy = 0;
Paul E. McKenney1d1fb392012-05-09 15:44:42 -07001969 ACCESS_ONCE(rdp->qlen) = 0;
Paul E. McKenneya50c3af2012-01-10 17:52:31 -08001970 }
1971
1972 /*
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001973 * Next, move those callbacks still needing a grace period to
1974 * the orphanage, where some other CPU will pick them up.
1975 * Some of the callbacks might have gone partway through a grace
1976 * period, but that is too bad. They get to start over because we
1977 * cannot assume that grace periods are synchronized across CPUs.
1978 * We don't bother updating the ->nxttail[] array yet, instead
1979 * we just reset the whole thing later on.
Paul E. McKenneya50c3af2012-01-10 17:52:31 -08001980 */
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001981 if (*rdp->nxttail[RCU_DONE_TAIL] != NULL) {
1982 *rsp->orphan_nxttail = *rdp->nxttail[RCU_DONE_TAIL];
1983 rsp->orphan_nxttail = rdp->nxttail[RCU_NEXT_TAIL];
1984 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
Paul E. McKenneya50c3af2012-01-10 17:52:31 -08001985 }
1986
1987 /*
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001988 * Then move the ready-to-invoke callbacks to the orphanage,
1989 * where some other CPU will pick them up. These will not be
1990 * required to pass though another grace period: They are done.
Paul E. McKenneya50c3af2012-01-10 17:52:31 -08001991 */
Paul E. McKenneye5601402012-01-07 11:03:57 -08001992 if (rdp->nxtlist != NULL) {
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001993 *rsp->orphan_donetail = rdp->nxtlist;
1994 rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
Paul E. McKenneye5601402012-01-07 11:03:57 -08001995 }
Lai Jiangshan29494be2010-10-20 14:13:06 +08001996
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001997 /* Finally, initialize the rcu_data structure's list to empty. */
Paul E. McKenney3f5d3ea2012-05-09 15:39:56 -07001998 init_callback_list(rdp);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08001999}
2000
2001/*
2002 * Adopt the RCU callbacks from the specified rcu_state structure's
Paul E. McKenney7b2e6012012-10-08 10:54:03 -07002003 * orphanage. The caller must hold the ->orphan_lock.
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002004 */
Paul E. McKenney96d3fd02013-10-04 14:33:34 -07002005static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002006{
2007 int i;
2008 struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
2009
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002010 /* No-CBs CPUs are handled specially. */
Paul E. McKenney96d3fd02013-10-04 14:33:34 -07002011 if (rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags))
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002012 return;
2013
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002014 /* Do the accounting first. */
2015 rdp->qlen_lazy += rsp->qlen_lazy;
2016 rdp->qlen += rsp->qlen;
2017 rdp->n_cbs_adopted += rsp->qlen;
Paul E. McKenney8f5af6f2012-05-04 08:31:53 -07002018 if (rsp->qlen_lazy != rsp->qlen)
2019 rcu_idle_count_callbacks_posted();
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002020 rsp->qlen_lazy = 0;
2021 rsp->qlen = 0;
2022
2023 /*
2024 * We do not need a memory barrier here because the only way we
2025 * can get here if there is an rcu_barrier() in flight is if
2026 * we are the task doing the rcu_barrier().
2027 */
2028
2029 /* First adopt the ready-to-invoke callbacks. */
2030 if (rsp->orphan_donelist != NULL) {
2031 *rsp->orphan_donetail = *rdp->nxttail[RCU_DONE_TAIL];
2032 *rdp->nxttail[RCU_DONE_TAIL] = rsp->orphan_donelist;
2033 for (i = RCU_NEXT_SIZE - 1; i >= RCU_DONE_TAIL; i--)
2034 if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
2035 rdp->nxttail[i] = rsp->orphan_donetail;
2036 rsp->orphan_donelist = NULL;
2037 rsp->orphan_donetail = &rsp->orphan_donelist;
2038 }
2039
2040 /* And then adopt the callbacks that still need a grace period. */
2041 if (rsp->orphan_nxtlist != NULL) {
2042 *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxtlist;
2043 rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_nxttail;
2044 rsp->orphan_nxtlist = NULL;
2045 rsp->orphan_nxttail = &rsp->orphan_nxtlist;
2046 }
2047}
2048
2049/*
2050 * Trace the fact that this CPU is going offline.
2051 */
2052static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
2053{
2054 RCU_TRACE(unsigned long mask);
2055 RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(rsp->rda));
2056 RCU_TRACE(struct rcu_node *rnp = rdp->mynode);
2057
2058 RCU_TRACE(mask = rdp->grpmask);
Paul E. McKenneye5601402012-01-07 11:03:57 -08002059 trace_rcu_grace_period(rsp->name,
2060 rnp->gpnum + 1 - !!(rnp->qsmask & mask),
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04002061 TPS("cpuofl"));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002062}
2063
2064/*
Paul E. McKenneye5601402012-01-07 11:03:57 -08002065 * The CPU has been completely removed, and some other CPU is reporting
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002066 * this fact from process context. Do the remainder of the cleanup,
2067 * including orphaning the outgoing CPU's RCU callbacks, and also
Paul E. McKenney1331e7a2012-08-02 17:43:50 -07002068 * adopting them. There can only be one CPU hotplug operation at a time,
2069 * so no other CPU can be attempting to update rcu_cpu_kthread_task.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002070 */
Paul E. McKenneye5601402012-01-07 11:03:57 -08002071static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002072{
Paul E. McKenney2036d942012-01-30 17:02:47 -08002073 unsigned long flags;
2074 unsigned long mask;
2075 int need_report = 0;
Paul E. McKenneye5601402012-01-07 11:03:57 -08002076 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002077 struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
Paul E. McKenneye5601402012-01-07 11:03:57 -08002078
Paul E. McKenney2036d942012-01-30 17:02:47 -08002079 /* Adjust any no-longer-needed kthreads. */
Thomas Gleixner5d01bbd2012-07-16 10:42:35 +00002080 rcu_boost_kthread_setaffinity(rnp, -1);
Paul E. McKenney2036d942012-01-30 17:02:47 -08002081
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002082 /* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
Paul E. McKenney2036d942012-01-30 17:02:47 -08002083
2084 /* Exclude any attempts to start a new grace period. */
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07002085 mutex_lock(&rsp->onoff_mutex);
Paul E. McKenney7b2e6012012-10-08 10:54:03 -07002086 raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
Paul E. McKenney2036d942012-01-30 17:02:47 -08002087
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002088 /* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
2089 rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
Paul E. McKenney96d3fd02013-10-04 14:33:34 -07002090 rcu_adopt_orphan_cbs(rsp, flags);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002091
Paul E. McKenney2036d942012-01-30 17:02:47 -08002092 /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
2093 mask = rdp->grpmask; /* rnp->grplo is constant. */
2094 do {
2095 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08002096 smp_mb__after_unlock_lock();
Paul E. McKenney2036d942012-01-30 17:02:47 -08002097 rnp->qsmaskinit &= ~mask;
2098 if (rnp->qsmaskinit != 0) {
2099 if (rnp != rdp->mynode)
2100 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
2101 break;
2102 }
2103 if (rnp == rdp->mynode)
2104 need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
2105 else
2106 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
2107 mask = rnp->grpmask;
2108 rnp = rnp->parent;
2109 } while (rnp != NULL);
2110
2111 /*
2112 * We still hold the leaf rcu_node structure lock here, and
2113 * irqs are still disabled. The reason for this subterfuge is
Paul E. McKenney7b2e6012012-10-08 10:54:03 -07002114 * because invoking rcu_report_unblock_qs_rnp() with ->orphan_lock
Paul E. McKenney2036d942012-01-30 17:02:47 -08002115 * held leads to deadlock.
2116 */
Paul E. McKenney7b2e6012012-10-08 10:54:03 -07002117 raw_spin_unlock(&rsp->orphan_lock); /* irqs remain disabled. */
Paul E. McKenney2036d942012-01-30 17:02:47 -08002118 rnp = rdp->mynode;
2119 if (need_report & RCU_OFL_TASKS_NORM_GP)
2120 rcu_report_unblock_qs_rnp(rnp, flags);
2121 else
2122 raw_spin_unlock_irqrestore(&rnp->lock, flags);
2123 if (need_report & RCU_OFL_TASKS_EXP_GP)
2124 rcu_report_exp_rnp(rsp, rnp, true);
Paul E. McKenneycf015372012-06-21 11:26:42 -07002125 WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
2126 "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
2127 cpu, rdp->qlen, rdp->nxtlist);
Paul E. McKenney0d8ee372012-08-03 13:16:15 -07002128 init_callback_list(rdp);
2129 /* Disallow further callbacks on this CPU. */
2130 rdp->nxttail[RCU_NEXT_TAIL] = NULL;
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07002131 mutex_unlock(&rsp->onoff_mutex);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002132}
2133
2134#else /* #ifdef CONFIG_HOTPLUG_CPU */
2135
Paul E. McKenneye5601402012-01-07 11:03:57 -08002136static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07002137{
2138}
2139
Paul E. McKenneye5601402012-01-07 11:03:57 -08002140static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002141{
2142}
2143
2144#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
2145
2146/*
2147 * Invoke any RCU callbacks that have made it to the end of their grace
2148 * period. Thottle as specified by rdp->blimit.
2149 */
Paul E. McKenney37c72e52009-10-14 10:15:55 -07002150static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002151{
2152 unsigned long flags;
2153 struct rcu_head *next, *list, **tail;
Eric Dumazet878d7432012-10-18 04:55:36 -07002154 long bl, count, count_lazy;
2155 int i;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002156
Paul E. McKenneydc35c892012-12-03 13:52:00 -08002157 /* If no callbacks are ready, just return. */
Paul E. McKenney29c00b42011-06-17 15:53:19 -07002158 if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
Paul E. McKenney486e2592012-01-06 14:11:30 -08002159 trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
Paul E. McKenney4968c302011-12-07 16:32:40 -08002160 trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
2161 need_resched(), is_idle_task(current),
2162 rcu_is_callbacks_kthread());
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002163 return;
Paul E. McKenney29c00b42011-06-17 15:53:19 -07002164 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002165
2166 /*
2167 * Extract the list of ready callbacks, disabling to prevent
2168 * races with call_rcu() from interrupt handlers.
2169 */
2170 local_irq_save(flags);
Paul E. McKenney8146c4e22012-01-10 14:23:29 -08002171 WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
Paul E. McKenney29c00b42011-06-17 15:53:19 -07002172 bl = rdp->blimit;
Paul E. McKenney486e2592012-01-06 14:11:30 -08002173 trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002174 list = rdp->nxtlist;
2175 rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
2176 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
2177 tail = rdp->nxttail[RCU_DONE_TAIL];
Paul E. McKenneyb41772a2012-06-21 20:50:42 -07002178 for (i = RCU_NEXT_SIZE - 1; i >= 0; i--)
2179 if (rdp->nxttail[i] == rdp->nxttail[RCU_DONE_TAIL])
2180 rdp->nxttail[i] = &rdp->nxtlist;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002181 local_irq_restore(flags);
2182
2183 /* Invoke callbacks. */
Paul E. McKenney486e2592012-01-06 14:11:30 -08002184 count = count_lazy = 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002185 while (list) {
2186 next = list->next;
2187 prefetch(next);
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -04002188 debug_rcu_head_unqueue(list);
Paul E. McKenney486e2592012-01-06 14:11:30 -08002189 if (__rcu_reclaim(rsp->name, list))
2190 count_lazy++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002191 list = next;
Paul E. McKenneydff16722011-11-29 15:57:13 -08002192 /* Stop only if limit reached and CPU has something to do. */
2193 if (++count >= bl &&
2194 (need_resched() ||
2195 (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002196 break;
2197 }
2198
2199 local_irq_save(flags);
Paul E. McKenney4968c302011-12-07 16:32:40 -08002200 trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
2201 is_idle_task(current),
2202 rcu_is_callbacks_kthread());
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002203
2204 /* Update count, and requeue any remaining callbacks. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002205 if (list != NULL) {
2206 *tail = rdp->nxtlist;
2207 rdp->nxtlist = list;
Paul E. McKenneyb41772a2012-06-21 20:50:42 -07002208 for (i = 0; i < RCU_NEXT_SIZE; i++)
2209 if (&rdp->nxtlist == rdp->nxttail[i])
2210 rdp->nxttail[i] = tail;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002211 else
2212 break;
2213 }
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002214 smp_mb(); /* List handling before counting for rcu_barrier(). */
2215 rdp->qlen_lazy -= count_lazy;
Paul E. McKenney1d1fb392012-05-09 15:44:42 -07002216 ACCESS_ONCE(rdp->qlen) -= count;
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08002217 rdp->n_cbs_invoked += count;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002218
2219 /* Reinstate batch limit if we have worked down the excess. */
2220 if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
2221 rdp->blimit = blimit;
2222
Paul E. McKenney37c72e52009-10-14 10:15:55 -07002223 /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
2224 if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
2225 rdp->qlen_last_fqs_check = 0;
2226 rdp->n_force_qs_snap = rsp->n_force_qs;
2227 } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
2228 rdp->qlen_last_fqs_check = rdp->qlen;
Paul E. McKenneycfca9272012-06-25 12:54:17 -07002229 WARN_ON_ONCE((rdp->nxtlist == NULL) != (rdp->qlen == 0));
Paul E. McKenney37c72e52009-10-14 10:15:55 -07002230
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002231 local_irq_restore(flags);
2232
Paul E. McKenneye0f23062011-06-21 01:29:39 -07002233 /* Re-invoke RCU core processing if there are callbacks remaining. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002234 if (cpu_has_callbacks_ready_to_invoke(rdp))
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002235 invoke_rcu_core();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002236}
2237
2238/*
2239 * Check to see if this CPU is in a non-context-switch quiescent state
2240 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
Paul E. McKenneye0f23062011-06-21 01:29:39 -07002241 * Also schedule RCU core processing.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002242 *
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -07002243 * This function must be called from hardirq context. It is normally
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002244 * invoked from the scheduling-clock interrupt. If rcu_pending returns
2245 * false, there is no point in invoking rcu_check_callbacks().
2246 */
2247void rcu_check_callbacks(int cpu, int user)
2248{
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04002249 trace_rcu_utilization(TPS("Start scheduler-tick"));
Paul E. McKenneya858af22012-01-16 13:29:10 -08002250 increment_cpu_stall_ticks();
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -07002251 if (user || rcu_is_cpu_rrupt_from_idle()) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002252
2253 /*
2254 * Get here if this CPU took its interrupt from user
2255 * mode or from the idle loop, and if this is not a
2256 * nested interrupt. In this case, the CPU is in
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002257 * a quiescent state, so note it.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002258 *
2259 * No memory barrier is required here because both
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002260 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
2261 * variables that other CPUs neither access nor modify,
2262 * at least not while the corresponding CPU is online.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002263 */
2264
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002265 rcu_sched_qs(cpu);
2266 rcu_bh_qs(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002267
2268 } else if (!in_softirq()) {
2269
2270 /*
2271 * Get here if this CPU did not take its interrupt from
2272 * softirq, in other words, if it is not interrupting
2273 * a rcu_bh read-side critical section. This is an _bh
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002274 * critical section, so note it.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002275 */
2276
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002277 rcu_bh_qs(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002278 }
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07002279 rcu_preempt_check_callbacks(cpu);
Paul E. McKenneyd21670a2010-04-14 17:39:26 -07002280 if (rcu_pending(cpu))
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002281 invoke_rcu_core();
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04002282 trace_rcu_utilization(TPS("End scheduler-tick"));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002283}
2284
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002285/*
2286 * Scan the leaf rcu_node structures, processing dyntick state for any that
2287 * have not yet encountered a quiescent state, using the function specified.
Paul E. McKenney27f4d282011-02-07 12:47:15 -08002288 * Also initiate boosting for any threads blocked on the root rcu_node.
2289 *
Paul E. McKenneyee47eb92010-01-04 15:09:07 -08002290 * The caller must have suppressed start of new grace periods.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002291 */
Paul E. McKenney217af2a2013-06-21 15:39:06 -07002292static void force_qs_rnp(struct rcu_state *rsp,
2293 int (*f)(struct rcu_data *rsp, bool *isidle,
2294 unsigned long *maxj),
2295 bool *isidle, unsigned long *maxj)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002296{
2297 unsigned long bit;
2298 int cpu;
2299 unsigned long flags;
2300 unsigned long mask;
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07002301 struct rcu_node *rnp;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002302
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07002303 rcu_for_each_leaf_node(rsp, rnp) {
Paul E. McKenneyb4be093f2012-06-25 08:41:11 -07002304 cond_resched();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002305 mask = 0;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08002306 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08002307 smp_mb__after_unlock_lock();
Paul E. McKenneyee47eb92010-01-04 15:09:07 -08002308 if (!rcu_gp_in_progress(rsp)) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08002309 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney0f10dc822010-01-04 15:09:06 -08002310 return;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002311 }
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07002312 if (rnp->qsmask == 0) {
Paul E. McKenney1217ed12011-05-04 21:43:49 -07002313 rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002314 continue;
2315 }
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07002316 cpu = rnp->grplo;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002317 bit = 1;
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07002318 for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
Paul E. McKenney0edd1b12013-06-21 16:37:22 -07002319 if ((rnp->qsmask & bit) != 0) {
2320 if ((rnp->qsmaskinit & bit) != 0)
2321 *isidle = 0;
2322 if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
2323 mask |= bit;
2324 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002325 }
Paul E. McKenney45f014c52e2010-01-04 15:09:08 -08002326 if (mask != 0) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002327
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08002328 /* rcu_report_qs_rnp() releases rnp->lock. */
2329 rcu_report_qs_rnp(mask, rsp, rnp, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002330 continue;
2331 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08002332 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002333 }
Paul E. McKenney27f4d282011-02-07 12:47:15 -08002334 rnp = rcu_get_root(rsp);
Paul E. McKenney1217ed12011-05-04 21:43:49 -07002335 if (rnp->qsmask == 0) {
2336 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08002337 smp_mb__after_unlock_lock();
Paul E. McKenney1217ed12011-05-04 21:43:49 -07002338 rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
2339 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002340}
2341
2342/*
2343 * Force quiescent states on reluctant CPUs, and also detect which
2344 * CPUs are in dyntick-idle mode.
2345 */
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07002346static void force_quiescent_state(struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002347{
2348 unsigned long flags;
Paul E. McKenney394f2762012-06-26 17:00:35 -07002349 bool ret;
2350 struct rcu_node *rnp;
2351 struct rcu_node *rnp_old = NULL;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002352
Paul E. McKenney394f2762012-06-26 17:00:35 -07002353 /* Funnel through hierarchy to reduce memory contention. */
2354 rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
2355 for (; rnp != NULL; rnp = rnp->parent) {
2356 ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
2357 !raw_spin_trylock(&rnp->fqslock);
2358 if (rnp_old != NULL)
2359 raw_spin_unlock(&rnp_old->fqslock);
2360 if (ret) {
Paul E. McKenney3660c282013-12-03 09:24:02 -08002361 ACCESS_ONCE(rsp->n_force_qs_lh)++;
Paul E. McKenney394f2762012-06-26 17:00:35 -07002362 return;
2363 }
2364 rnp_old = rnp;
2365 }
2366 /* rnp_old == rcu_get_root(rsp), rnp == NULL. */
2367
2368 /* Reached the root of the rcu_node tree, acquire lock. */
2369 raw_spin_lock_irqsave(&rnp_old->lock, flags);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08002370 smp_mb__after_unlock_lock();
Paul E. McKenney394f2762012-06-26 17:00:35 -07002371 raw_spin_unlock(&rnp_old->fqslock);
2372 if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
Paul E. McKenney3660c282013-12-03 09:24:02 -08002373 ACCESS_ONCE(rsp->n_force_qs_lh)++;
Paul E. McKenney394f2762012-06-26 17:00:35 -07002374 raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07002375 return; /* Someone beat us to it. */
Paul E. McKenney46a1e342010-01-04 15:09:09 -08002376 }
Paul E. McKenney91dc9542014-02-18 09:47:13 -08002377 ACCESS_ONCE(rsp->gp_flags) |= RCU_GP_FLAG_FQS;
Paul E. McKenney394f2762012-06-26 17:00:35 -07002378 raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07002379 wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002380}
2381
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002382/*
Paul E. McKenneye0f23062011-06-21 01:29:39 -07002383 * This does the RCU core processing work for the specified rcu_state
2384 * and rcu_data structures. This may be called only from the CPU to
2385 * whom the rdp belongs.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002386 */
2387static void
Paul E. McKenney1bca8cf2012-06-12 09:40:38 -07002388__rcu_process_callbacks(struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002389{
2390 unsigned long flags;
Paul E. McKenney48a76392014-03-11 13:02:16 -07002391 bool needwake;
Paul E. McKenney1bca8cf2012-06-12 09:40:38 -07002392 struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002393
Paul E. McKenney2e597552009-08-15 09:53:48 -07002394 WARN_ON_ONCE(rdp->beenonline == 0);
2395
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002396 /* Update RCU state based on any recent quiescent states. */
2397 rcu_check_quiescent_state(rsp, rdp);
2398
2399 /* Does this CPU require a not-yet-started grace period? */
Paul E. McKenneydc35c892012-12-03 13:52:00 -08002400 local_irq_save(flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002401 if (cpu_needs_another_gp(rsp, rdp)) {
Paul E. McKenneydc35c892012-12-03 13:52:00 -08002402 raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
Paul E. McKenney48a76392014-03-11 13:02:16 -07002403 needwake = rcu_start_gp(rsp);
Paul E. McKenneyb8462082012-12-29 22:04:18 -08002404 raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
Paul E. McKenney48a76392014-03-11 13:02:16 -07002405 if (needwake)
2406 rcu_gp_kthread_wake(rsp);
Paul E. McKenneydc35c892012-12-03 13:52:00 -08002407 } else {
2408 local_irq_restore(flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002409 }
2410
2411 /* If there are callbacks ready, invoke them. */
Shaohua Li09223372011-06-14 13:26:25 +08002412 if (cpu_has_callbacks_ready_to_invoke(rdp))
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002413 invoke_rcu_callbacks(rsp, rdp);
Paul E. McKenney96d3fd02013-10-04 14:33:34 -07002414
2415 /* Do any needed deferred wakeups of rcuo kthreads. */
2416 do_nocb_deferred_wakeup(rdp);
Shaohua Li09223372011-06-14 13:26:25 +08002417}
2418
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002419/*
Paul E. McKenneye0f23062011-06-21 01:29:39 -07002420 * Do RCU core processing for the current CPU.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002421 */
Shaohua Li09223372011-06-14 13:26:25 +08002422static void rcu_process_callbacks(struct softirq_action *unused)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002423{
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07002424 struct rcu_state *rsp;
2425
Paul E. McKenneybfa00b42012-06-21 09:54:10 -07002426 if (cpu_is_offline(smp_processor_id()))
2427 return;
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04002428 trace_rcu_utilization(TPS("Start RCU core"));
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07002429 for_each_rcu_flavor(rsp)
2430 __rcu_process_callbacks(rsp);
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04002431 trace_rcu_utilization(TPS("End RCU core"));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002432}
2433
Paul E. McKenneya26ac242011-01-12 14:10:23 -08002434/*
Paul E. McKenneye0f23062011-06-21 01:29:39 -07002435 * Schedule RCU callback invocation. If the specified type of RCU
2436 * does not support RCU priority boosting, just do a direct call,
2437 * otherwise wake up the per-CPU kernel kthread. Note that because we
2438 * are running on the current CPU with interrupts disabled, the
2439 * rcu_cpu_kthread_task cannot disappear out from under us.
Paul E. McKenneya26ac242011-01-12 14:10:23 -08002440 */
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002441static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
Paul E. McKenneya26ac242011-01-12 14:10:23 -08002442{
Paul E. McKenneyb0d30412011-07-10 15:57:35 -07002443 if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
2444 return;
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002445 if (likely(!rsp->boost)) {
2446 rcu_do_batch(rsp, rdp);
Paul E. McKenneya26ac242011-01-12 14:10:23 -08002447 return;
2448 }
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002449 invoke_rcu_callbacks_kthread();
Paul E. McKenneya26ac242011-01-12 14:10:23 -08002450}
2451
Paul E. McKenneya46e0892011-06-15 15:47:09 -07002452static void invoke_rcu_core(void)
Shaohua Li09223372011-06-14 13:26:25 +08002453{
Paul E. McKenneyb0f74032013-02-04 12:14:24 -08002454 if (cpu_online(smp_processor_id()))
2455 raise_softirq(RCU_SOFTIRQ);
Shaohua Li09223372011-06-14 13:26:25 +08002456}
2457
Paul E. McKenney29154c52012-05-30 03:21:48 -07002458/*
2459 * Handle any core-RCU processing required by a call_rcu() invocation.
2460 */
2461static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
2462 struct rcu_head *head, unsigned long flags)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002463{
Paul E. McKenney48a76392014-03-11 13:02:16 -07002464 bool needwake;
2465
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002466 /*
Paul E. McKenney29154c52012-05-30 03:21:48 -07002467 * If called from an extended quiescent state, invoke the RCU
2468 * core in order to force a re-evaluation of RCU's idleness.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002469 */
Paul E. McKenney5c173eb2013-09-13 17:20:11 -07002470 if (!rcu_is_watching() && cpu_online(smp_processor_id()))
Paul E. McKenney29154c52012-05-30 03:21:48 -07002471 invoke_rcu_core();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002472
Paul E. McKenney29154c52012-05-30 03:21:48 -07002473 /* If interrupts were disabled or CPU offline, don't invoke RCU core. */
2474 if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id()))
Paul E. McKenney2655d572011-04-07 22:47:23 -07002475 return;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002476
Paul E. McKenney37c72e52009-10-14 10:15:55 -07002477 /*
2478 * Force the grace period if too many callbacks or too long waiting.
2479 * Enforce hysteresis, and don't invoke force_quiescent_state()
2480 * if some other CPU has recently done so. Also, don't bother
2481 * invoking force_quiescent_state() if the newly enqueued callback
2482 * is the only one waiting for a grace period to complete.
2483 */
Paul E. McKenney2655d572011-04-07 22:47:23 -07002484 if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
Paul E. McKenneyb52573d2010-12-14 17:36:02 -08002485
2486 /* Are we ignoring a completed grace period? */
Paul E. McKenney470716f2013-03-19 11:32:11 -07002487 note_gp_changes(rsp, rdp);
Paul E. McKenneyb52573d2010-12-14 17:36:02 -08002488
2489 /* Start a new grace period if one not already started. */
2490 if (!rcu_gp_in_progress(rsp)) {
Paul E. McKenneyb52573d2010-12-14 17:36:02 -08002491 struct rcu_node *rnp_root = rcu_get_root(rsp);
2492
Paul E. McKenneyb8462082012-12-29 22:04:18 -08002493 raw_spin_lock(&rnp_root->lock);
Paul E. McKenney6303b9c2013-12-11 13:59:10 -08002494 smp_mb__after_unlock_lock();
Paul E. McKenney48a76392014-03-11 13:02:16 -07002495 needwake = rcu_start_gp(rsp);
Paul E. McKenneyb8462082012-12-29 22:04:18 -08002496 raw_spin_unlock(&rnp_root->lock);
Paul E. McKenney48a76392014-03-11 13:02:16 -07002497 if (needwake)
2498 rcu_gp_kthread_wake(rsp);
Paul E. McKenneyb52573d2010-12-14 17:36:02 -08002499 } else {
2500 /* Give the grace period a kick. */
2501 rdp->blimit = LONG_MAX;
2502 if (rsp->n_force_qs == rdp->n_force_qs_snap &&
2503 *rdp->nxttail[RCU_DONE_TAIL] != head)
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07002504 force_quiescent_state(rsp);
Paul E. McKenneyb52573d2010-12-14 17:36:02 -08002505 rdp->n_force_qs_snap = rsp->n_force_qs;
2506 rdp->qlen_last_fqs_check = rdp->qlen;
2507 }
Paul E. McKenney4cdfc172012-06-22 17:06:26 -07002508 }
Paul E. McKenney29154c52012-05-30 03:21:48 -07002509}
2510
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002511/*
Paul E. McKenneyae150182013-04-23 13:20:57 -07002512 * RCU callback function to leak a callback.
2513 */
2514static void rcu_leak_callback(struct rcu_head *rhp)
2515{
2516}
2517
2518/*
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002519 * Helper function for call_rcu() and friends. The cpu argument will
2520 * normally be -1, indicating "currently running CPU". It may specify
2521 * a CPU only if that CPU is a no-CBs CPU. Currently, only _rcu_barrier()
2522 * is expected to specify a CPU.
2523 */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002524static void
2525__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002526 struct rcu_state *rsp, int cpu, bool lazy)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002527{
2528 unsigned long flags;
2529 struct rcu_data *rdp;
2530
2531 WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
Paul E. McKenneyae150182013-04-23 13:20:57 -07002532 if (debug_rcu_head_queue(head)) {
2533 /* Probable double call_rcu(), so leak the callback. */
2534 ACCESS_ONCE(head->func) = rcu_leak_callback;
2535 WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n");
2536 return;
2537 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002538 head->func = func;
2539 head->next = NULL;
2540
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002541 /*
2542 * Opportunistically note grace-period endings and beginnings.
2543 * Note that we might see a beginning right after we see an
2544 * end, but never vice versa, since this CPU has to pass through
2545 * a quiescent state betweentimes.
2546 */
2547 local_irq_save(flags);
2548 rdp = this_cpu_ptr(rsp->rda);
2549
2550 /* Add the callback to our list. */
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002551 if (unlikely(rdp->nxttail[RCU_NEXT_TAIL] == NULL) || cpu != -1) {
2552 int offline;
2553
2554 if (cpu != -1)
2555 rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney96d3fd02013-10-04 14:33:34 -07002556 offline = !__call_rcu_nocb(rdp, head, lazy, flags);
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002557 WARN_ON_ONCE(offline);
Paul E. McKenney0d8ee372012-08-03 13:16:15 -07002558 /* _call_rcu() is illegal on offline CPU; leak the callback. */
Paul E. McKenney0d8ee372012-08-03 13:16:15 -07002559 local_irq_restore(flags);
2560 return;
2561 }
Paul E. McKenney1d1fb392012-05-09 15:44:42 -07002562 ACCESS_ONCE(rdp->qlen)++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002563 if (lazy)
2564 rdp->qlen_lazy++;
2565 else
2566 rcu_idle_count_callbacks_posted();
2567 smp_mb(); /* Count before adding callback for rcu_barrier(). */
2568 *rdp->nxttail[RCU_NEXT_TAIL] = head;
2569 rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
2570
2571 if (__is_kfree_rcu_offset((unsigned long)func))
2572 trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
2573 rdp->qlen_lazy, rdp->qlen);
2574 else
2575 trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
2576
Paul E. McKenney29154c52012-05-30 03:21:48 -07002577 /* Go handle any RCU core processing required. */
2578 __call_rcu_core(rsp, rdp, head, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002579 local_irq_restore(flags);
2580}
2581
2582/*
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002583 * Queue an RCU-sched callback for invocation after a grace period.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002584 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002585void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002586{
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002587 __call_rcu(head, func, &rcu_sched_state, -1, 0);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002588}
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07002589EXPORT_SYMBOL_GPL(call_rcu_sched);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002590
2591/*
Paul E. McKenney486e2592012-01-06 14:11:30 -08002592 * Queue an RCU callback for invocation after a quicker grace period.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002593 */
2594void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
2595{
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07002596 __call_rcu(head, func, &rcu_bh_state, -1, 0);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002597}
2598EXPORT_SYMBOL_GPL(call_rcu_bh);
2599
Paul E. McKenney6d813392012-02-23 13:30:16 -08002600/*
2601 * Because a context switch is a grace period for RCU-sched and RCU-bh,
2602 * any blocking grace-period wait automatically implies a grace period
2603 * if there is only one CPU online at any point time during execution
2604 * of either synchronize_sched() or synchronize_rcu_bh(). It is OK to
2605 * occasionally incorrectly indicate that there are multiple CPUs online
2606 * when there was in fact only one the whole time, as this just adds
2607 * some overhead: RCU still operates correctly.
Paul E. McKenney6d813392012-02-23 13:30:16 -08002608 */
2609static inline int rcu_blocking_is_gp(void)
2610{
Paul E. McKenney95f0c1d2012-06-19 11:58:27 -07002611 int ret;
2612
Paul E. McKenney6d813392012-02-23 13:30:16 -08002613 might_sleep(); /* Check for RCU read-side critical section. */
Paul E. McKenney95f0c1d2012-06-19 11:58:27 -07002614 preempt_disable();
2615 ret = num_online_cpus() <= 1;
2616 preempt_enable();
2617 return ret;
Paul E. McKenney6d813392012-02-23 13:30:16 -08002618}
2619
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002620/**
2621 * synchronize_sched - wait until an rcu-sched grace period has elapsed.
2622 *
2623 * Control will return to the caller some time after a full rcu-sched
2624 * grace period has elapsed, in other words after all currently executing
2625 * rcu-sched read-side critical sections have completed. These read-side
2626 * critical sections are delimited by rcu_read_lock_sched() and
2627 * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
2628 * local_irq_disable(), and so on may be used in place of
2629 * rcu_read_lock_sched().
2630 *
2631 * This means that all preempt_disable code sequences, including NMI and
Paul E. McKenneyf0a0e6f2012-10-23 13:47:01 -07002632 * non-threaded hardware-interrupt handlers, in progress on entry will
2633 * have completed before this primitive returns. However, this does not
2634 * guarantee that softirq handlers will have completed, since in some
2635 * kernels, these handlers can run in process context, and can block.
2636 *
2637 * Note that this guarantee implies further memory-ordering guarantees.
2638 * On systems with more than one CPU, when synchronize_sched() returns,
2639 * each CPU is guaranteed to have executed a full memory barrier since the
2640 * end of its last RCU-sched read-side critical section whose beginning
2641 * preceded the call to synchronize_sched(). In addition, each CPU having
2642 * an RCU read-side critical section that extends beyond the return from
2643 * synchronize_sched() is guaranteed to have executed a full memory barrier
2644 * after the beginning of synchronize_sched() and before the beginning of
2645 * that RCU read-side critical section. Note that these guarantees include
2646 * CPUs that are offline, idle, or executing in user mode, as well as CPUs
2647 * that are executing in the kernel.
2648 *
2649 * Furthermore, if CPU A invoked synchronize_sched(), which returned
2650 * to its caller on CPU B, then both CPU A and CPU B are guaranteed
2651 * to have executed a full memory barrier during the execution of
2652 * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but
2653 * again only if the system has more than one CPU).
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002654 *
2655 * This primitive provides the guarantees made by the (now removed)
2656 * synchronize_kernel() API. In contrast, synchronize_rcu() only
2657 * guarantees that rcu_read_lock() sections will have completed.
2658 * In "classic RCU", these two guarantees happen to be one and
2659 * the same, but can differ in realtime RCU implementations.
2660 */
2661void synchronize_sched(void)
2662{
Paul E. McKenneyfe15d702012-01-04 13:30:33 -08002663 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
2664 !lock_is_held(&rcu_lock_map) &&
2665 !lock_is_held(&rcu_sched_lock_map),
2666 "Illegal synchronize_sched() in RCU-sched read-side critical section");
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002667 if (rcu_blocking_is_gp())
2668 return;
Antti P Miettinen3705b882012-10-05 09:59:15 +03002669 if (rcu_expedited)
2670 synchronize_sched_expedited();
2671 else
2672 wait_rcu_gp(call_rcu_sched);
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002673}
2674EXPORT_SYMBOL_GPL(synchronize_sched);
2675
2676/**
2677 * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
2678 *
2679 * Control will return to the caller some time after a full rcu_bh grace
2680 * period has elapsed, in other words after all currently executing rcu_bh
2681 * read-side critical sections have completed. RCU read-side critical
2682 * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
2683 * and may be nested.
Paul E. McKenneyf0a0e6f2012-10-23 13:47:01 -07002684 *
2685 * See the description of synchronize_sched() for more detailed information
2686 * on memory ordering guarantees.
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002687 */
2688void synchronize_rcu_bh(void)
2689{
Paul E. McKenneyfe15d702012-01-04 13:30:33 -08002690 rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
2691 !lock_is_held(&rcu_lock_map) &&
2692 !lock_is_held(&rcu_sched_lock_map),
2693 "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002694 if (rcu_blocking_is_gp())
2695 return;
Antti P Miettinen3705b882012-10-05 09:59:15 +03002696 if (rcu_expedited)
2697 synchronize_rcu_bh_expedited();
2698 else
2699 wait_rcu_gp(call_rcu_bh);
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08002700}
2701EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
2702
Paul E. McKenney765a3f42014-03-14 16:37:08 -07002703/**
2704 * get_state_synchronize_rcu - Snapshot current RCU state
2705 *
2706 * Returns a cookie that is used by a later call to cond_synchronize_rcu()
2707 * to determine whether or not a full grace period has elapsed in the
2708 * meantime.
2709 */
2710unsigned long get_state_synchronize_rcu(void)
2711{
2712 /*
2713 * Any prior manipulation of RCU-protected data must happen
2714 * before the load from ->gpnum.
2715 */
2716 smp_mb(); /* ^^^ */
2717
2718 /*
2719 * Make sure this load happens before the purportedly
2720 * time-consuming work between get_state_synchronize_rcu()
2721 * and cond_synchronize_rcu().
2722 */
2723 return smp_load_acquire(&rcu_state->gpnum);
2724}
2725EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
2726
2727/**
2728 * cond_synchronize_rcu - Conditionally wait for an RCU grace period
2729 *
2730 * @oldstate: return value from earlier call to get_state_synchronize_rcu()
2731 *
2732 * If a full RCU grace period has elapsed since the earlier call to
2733 * get_state_synchronize_rcu(), just return. Otherwise, invoke
2734 * synchronize_rcu() to wait for a full grace period.
2735 *
2736 * Yes, this function does not take counter wrap into account. But
2737 * counter wrap is harmless. If the counter wraps, we have waited for
2738 * more than 2 billion grace periods (and way more on a 64-bit system!),
2739 * so waiting for one additional grace period should be just fine.
2740 */
2741void cond_synchronize_rcu(unsigned long oldstate)
2742{
2743 unsigned long newstate;
2744
2745 /*
2746 * Ensure that this load happens before any RCU-destructive
2747 * actions the caller might carry out after we return.
2748 */
2749 newstate = smp_load_acquire(&rcu_state->completed);
2750 if (ULONG_CMP_GE(oldstate, newstate))
2751 synchronize_rcu();
2752}
2753EXPORT_SYMBOL_GPL(cond_synchronize_rcu);
2754
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002755static int synchronize_sched_expedited_cpu_stop(void *data)
2756{
2757 /*
2758 * There must be a full memory barrier on each affected CPU
2759 * between the time that try_stop_cpus() is called and the
2760 * time that it returns.
2761 *
2762 * In the current initial implementation of cpu_stop, the
2763 * above condition is already met when the control reaches
2764 * this point and the following smp_mb() is not strictly
2765 * necessary. Do smp_mb() anyway for documentation and
2766 * robustness against future implementation changes.
2767 */
2768 smp_mb(); /* See above comment block. */
2769 return 0;
2770}
2771
Paul E. McKenney236fefa2012-01-31 14:00:41 -08002772/**
2773 * synchronize_sched_expedited - Brute-force RCU-sched grace period
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002774 *
Paul E. McKenney236fefa2012-01-31 14:00:41 -08002775 * Wait for an RCU-sched grace period to elapse, but use a "big hammer"
2776 * approach to force the grace period to end quickly. This consumes
2777 * significant time on all CPUs and is unfriendly to real-time workloads,
2778 * so is thus not recommended for any sort of common-case code. In fact,
2779 * if you are using synchronize_sched_expedited() in a loop, please
2780 * restructure your code to batch your updates, and then use a single
2781 * synchronize_sched() instead.
2782 *
2783 * Note that it is illegal to call this function while holding any lock
2784 * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
2785 * to call this function from a CPU-hotplug notifier. Failing to observe
2786 * these restriction will result in deadlock.
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002787 *
2788 * This implementation can be thought of as an application of ticket
2789 * locking to RCU, with sync_sched_expedited_started and
2790 * sync_sched_expedited_done taking on the roles of the halves
2791 * of the ticket-lock word. Each task atomically increments
2792 * sync_sched_expedited_started upon entry, snapshotting the old value,
2793 * then attempts to stop all the CPUs. If this succeeds, then each
2794 * CPU will have executed a context switch, resulting in an RCU-sched
2795 * grace period. We are then done, so we use atomic_cmpxchg() to
2796 * update sync_sched_expedited_done to match our snapshot -- but
2797 * only if someone else has not already advanced past our snapshot.
2798 *
2799 * On the other hand, if try_stop_cpus() fails, we check the value
2800 * of sync_sched_expedited_done. If it has advanced past our
2801 * initial snapshot, then someone else must have forced a grace period
2802 * some time after we took our snapshot. In this case, our work is
2803 * done for us, and we can simply return. Otherwise, we try again,
2804 * but keep our initial snapshot for purposes of checking for someone
2805 * doing our work for us.
2806 *
2807 * If we fail too many times in a row, we fall back to synchronize_sched().
2808 */
2809void synchronize_sched_expedited(void)
2810{
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002811 long firstsnap, s, snap;
2812 int trycount = 0;
Paul E. McKenney40694d62012-10-11 15:24:03 -07002813 struct rcu_state *rsp = &rcu_sched_state;
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002814
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002815 /*
2816 * If we are in danger of counter wrap, just do synchronize_sched().
2817 * By allowing sync_sched_expedited_started to advance no more than
2818 * ULONG_MAX/8 ahead of sync_sched_expedited_done, we are ensuring
2819 * that more than 3.5 billion CPUs would be required to force a
2820 * counter wrap on a 32-bit system. Quite a few more CPUs would of
2821 * course be required on a 64-bit system.
2822 */
Paul E. McKenney40694d62012-10-11 15:24:03 -07002823 if (ULONG_CMP_GE((ulong)atomic_long_read(&rsp->expedited_start),
2824 (ulong)atomic_long_read(&rsp->expedited_done) +
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002825 ULONG_MAX / 8)) {
2826 synchronize_sched();
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002827 atomic_long_inc(&rsp->expedited_wrap);
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002828 return;
2829 }
2830
2831 /*
2832 * Take a ticket. Note that atomic_inc_return() implies a
2833 * full memory barrier.
2834 */
Paul E. McKenney40694d62012-10-11 15:24:03 -07002835 snap = atomic_long_inc_return(&rsp->expedited_start);
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002836 firstsnap = snap;
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002837 get_online_cpus();
Hugh Dickins1cc85962012-02-17 13:20:31 -08002838 WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002839
2840 /*
2841 * Each pass through the following loop attempts to force a
2842 * context switch on each CPU.
2843 */
2844 while (try_stop_cpus(cpu_online_mask,
2845 synchronize_sched_expedited_cpu_stop,
2846 NULL) == -EAGAIN) {
2847 put_online_cpus();
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002848 atomic_long_inc(&rsp->expedited_tryfail);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002849
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002850 /* Check to see if someone else did our work for us. */
Paul E. McKenney40694d62012-10-11 15:24:03 -07002851 s = atomic_long_read(&rsp->expedited_done);
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002852 if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002853 /* ensure test happens before caller kfree */
2854 smp_mb__before_atomic_inc(); /* ^^^ */
2855 atomic_long_inc(&rsp->expedited_workdone1);
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002856 return;
2857 }
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002858
2859 /* No joy, try again later. Or just synchronize_sched(). */
Paul E. McKenneyc701d5d2012-06-28 08:08:25 -07002860 if (trycount++ < 10) {
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002861 udelay(trycount * num_online_cpus());
Paul E. McKenneyc701d5d2012-06-28 08:08:25 -07002862 } else {
Antti P Miettinen3705b882012-10-05 09:59:15 +03002863 wait_rcu_gp(call_rcu_sched);
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002864 atomic_long_inc(&rsp->expedited_normal);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002865 return;
2866 }
2867
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002868 /* Recheck to see if someone else did our work for us. */
Paul E. McKenney40694d62012-10-11 15:24:03 -07002869 s = atomic_long_read(&rsp->expedited_done);
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002870 if (ULONG_CMP_GE((ulong)s, (ulong)firstsnap)) {
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002871 /* ensure test happens before caller kfree */
2872 smp_mb__before_atomic_inc(); /* ^^^ */
2873 atomic_long_inc(&rsp->expedited_workdone2);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002874 return;
2875 }
2876
2877 /*
2878 * Refetching sync_sched_expedited_started allows later
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002879 * callers to piggyback on our grace period. We retry
2880 * after they started, so our grace period works for them,
2881 * and they started after our first try, so their grace
2882 * period works for us.
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002883 */
2884 get_online_cpus();
Paul E. McKenney40694d62012-10-11 15:24:03 -07002885 snap = atomic_long_read(&rsp->expedited_start);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002886 smp_mb(); /* ensure read is before try_stop_cpus(). */
2887 }
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002888 atomic_long_inc(&rsp->expedited_stoppedcpus);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002889
2890 /*
2891 * Everyone up to our most recent fetch is covered by our grace
2892 * period. Update the counter, but only if our work is still
2893 * relevant -- which it won't be if someone who started later
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002894 * than we did already did their update.
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002895 */
2896 do {
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002897 atomic_long_inc(&rsp->expedited_done_tries);
Paul E. McKenney40694d62012-10-11 15:24:03 -07002898 s = atomic_long_read(&rsp->expedited_done);
Paul E. McKenney1924bcb2012-10-11 12:30:37 -07002899 if (ULONG_CMP_GE((ulong)s, (ulong)snap)) {
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002900 /* ensure test happens before caller kfree */
2901 smp_mb__before_atomic_inc(); /* ^^^ */
2902 atomic_long_inc(&rsp->expedited_done_lost);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002903 break;
2904 }
Paul E. McKenney40694d62012-10-11 15:24:03 -07002905 } while (atomic_long_cmpxchg(&rsp->expedited_done, s, snap) != s);
Paul E. McKenneya30489c2012-10-11 16:18:09 -07002906 atomic_long_inc(&rsp->expedited_done_exit);
Paul E. McKenney3d3b7db2012-01-23 17:05:46 -08002907
2908 put_online_cpus();
2909}
2910EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
2911
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002912/*
2913 * Check to see if there is any immediate RCU-related work to be done
2914 * by the current CPU, for the specified type of RCU, returning 1 if so.
2915 * The checks are in order of increasing expense: checks that can be
2916 * carried out against CPU-local state are performed first. However,
2917 * we must check for CPU stalls first, else we might not get a chance.
2918 */
2919static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
2920{
Paul E. McKenney2f51f982009-11-13 19:51:39 -08002921 struct rcu_node *rnp = rdp->mynode;
2922
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002923 rdp->n_rcu_pending++;
2924
2925 /* Check for CPU stalls, if enabled. */
2926 check_cpu_stall(rsp, rdp);
2927
Paul E. McKenneya0969322013-11-08 09:03:10 -08002928 /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */
2929 if (rcu_nohz_full_cpu(rsp))
2930 return 0;
2931
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002932 /* Is the RCU core waiting for a quiescent state from this CPU? */
Paul E. McKenney5c51dd72011-08-04 06:59:03 -07002933 if (rcu_scheduler_fully_active &&
2934 rdp->qs_pending && !rdp->passed_quiesce) {
Paul E. McKenneyd21670a2010-04-14 17:39:26 -07002935 rdp->n_rp_qs_pending++;
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07002936 } else if (rdp->qs_pending && rdp->passed_quiesce) {
Paul E. McKenneyd21670a2010-04-14 17:39:26 -07002937 rdp->n_rp_report_qs++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002938 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002939 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002940
2941 /* Does this CPU have callbacks ready to invoke? */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002942 if (cpu_has_callbacks_ready_to_invoke(rdp)) {
2943 rdp->n_rp_cb_ready++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002944 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002945 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002946
2947 /* Has RCU gone idle with this CPU needing another grace period? */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002948 if (cpu_needs_another_gp(rsp, rdp)) {
2949 rdp->n_rp_cpu_needs_gp++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002950 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002951 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002952
2953 /* Has another RCU grace period completed? */
Paul E. McKenney2f51f982009-11-13 19:51:39 -08002954 if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002955 rdp->n_rp_gp_completed++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002956 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002957 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002958
2959 /* Has a new RCU grace period started? */
Paul E. McKenney2f51f982009-11-13 19:51:39 -08002960 if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002961 rdp->n_rp_gp_started++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002962 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002963 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002964
Paul E. McKenney96d3fd02013-10-04 14:33:34 -07002965 /* Does this CPU need a deferred NOCB wakeup? */
2966 if (rcu_nocb_need_deferred_wakeup(rdp)) {
2967 rdp->n_rp_nocb_defer_wakeup++;
2968 return 1;
2969 }
2970
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002971 /* nothing to do */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07002972 rdp->n_rp_need_nothing++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002973 return 0;
2974}
2975
2976/*
2977 * Check to see if there is any immediate RCU-related work to be done
2978 * by the current CPU, returning 1 if so. This function is part of the
2979 * RCU implementation; it is -not- an exported member of the RCU API.
2980 */
Paul E. McKenneya1572292009-08-22 13:56:51 -07002981static int rcu_pending(int cpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002982{
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07002983 struct rcu_state *rsp;
2984
2985 for_each_rcu_flavor(rsp)
2986 if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu)))
2987 return 1;
2988 return 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002989}
2990
2991/*
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002992 * Return true if the specified CPU has any callback. If all_lazy is
2993 * non-NULL, store an indication of whether all callbacks are lazy.
2994 * (If there are no callbacks, all of them are deemed to be lazy.)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002995 */
Paul E. McKenneyffa83fb2013-11-17 19:27:16 -08002996static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002997{
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08002998 bool al = true;
2999 bool hc = false;
3000 struct rcu_data *rdp;
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07003001 struct rcu_state *rsp;
3002
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003003 for_each_rcu_flavor(rsp) {
3004 rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney69c8d282013-09-03 09:52:20 -07003005 if (!rdp->nxtlist)
3006 continue;
3007 hc = true;
3008 if (rdp->qlen != rdp->qlen_lazy || !all_lazy) {
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003009 al = false;
Paul E. McKenney69c8d282013-09-03 09:52:20 -07003010 break;
3011 }
Paul E. McKenneyc0f4dfd2012-12-28 11:30:36 -08003012 }
3013 if (all_lazy)
3014 *all_lazy = al;
3015 return hc;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003016}
3017
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003018/*
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003019 * Helper function for _rcu_barrier() tracing. If tracing is disabled,
3020 * the compiler is expected to optimize this away.
3021 */
Steven Rostedt (Red Hat)e66c33d2013-07-12 16:50:28 -04003022static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s,
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003023 int cpu, unsigned long done)
3024{
3025 trace_rcu_barrier(rsp->name, s, cpu,
3026 atomic_read(&rsp->barrier_cpu_count), done);
3027}
3028
3029/*
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003030 * RCU callback function for _rcu_barrier(). If we are last, wake
3031 * up the task executing _rcu_barrier().
3032 */
Paul E. McKenney24ebbca2012-05-29 00:34:56 -07003033static void rcu_barrier_callback(struct rcu_head *rhp)
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003034{
Paul E. McKenney24ebbca2012-05-29 00:34:56 -07003035 struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head);
3036 struct rcu_state *rsp = rdp->rsp;
3037
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003038 if (atomic_dec_and_test(&rsp->barrier_cpu_count)) {
3039 _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done);
Paul E. McKenney7db74df2012-05-29 03:03:37 -07003040 complete(&rsp->barrier_completion);
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003041 } else {
3042 _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done);
3043 }
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003044}
3045
3046/*
3047 * Called with preemption disabled, and from cross-cpu IRQ context.
3048 */
3049static void rcu_barrier_func(void *type)
3050{
Paul E. McKenney037b64e2012-05-28 23:26:01 -07003051 struct rcu_state *rsp = type;
Paul E. McKenney06668ef2012-05-28 23:57:46 -07003052 struct rcu_data *rdp = __this_cpu_ptr(rsp->rda);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003053
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003054 _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done);
Paul E. McKenney24ebbca2012-05-29 00:34:56 -07003055 atomic_inc(&rsp->barrier_cpu_count);
Paul E. McKenney06668ef2012-05-28 23:57:46 -07003056 rsp->call(&rdp->barrier_head, rcu_barrier_callback);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003057}
3058
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003059/*
3060 * Orchestrate the specified type of RCU barrier, waiting for all
3061 * RCU callbacks of the specified type to complete.
3062 */
Paul E. McKenney037b64e2012-05-28 23:26:01 -07003063static void _rcu_barrier(struct rcu_state *rsp)
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003064{
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003065 int cpu;
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003066 struct rcu_data *rdp;
Paul E. McKenneycf3a9c42012-05-29 14:56:46 -07003067 unsigned long snap = ACCESS_ONCE(rsp->n_barrier_done);
3068 unsigned long snap_done;
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003069
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003070 _rcu_barrier_trace(rsp, "Begin", -1, snap);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003071
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07003072 /* Take mutex to serialize concurrent rcu_barrier() requests. */
Paul E. McKenney7be7f0b2012-05-29 05:18:53 -07003073 mutex_lock(&rsp->barrier_mutex);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003074
Paul E. McKenneycf3a9c42012-05-29 14:56:46 -07003075 /*
3076 * Ensure that all prior references, including to ->n_barrier_done,
3077 * are ordered before the _rcu_barrier() machinery.
3078 */
3079 smp_mb(); /* See above block comment. */
3080
3081 /*
3082 * Recheck ->n_barrier_done to see if others did our work for us.
3083 * This means checking ->n_barrier_done for an even-to-odd-to-even
3084 * transition. The "if" expression below therefore rounds the old
3085 * value up to the next even number and adds two before comparing.
3086 */
Paul E. McKenney458fb382013-07-26 20:47:42 -07003087 snap_done = rsp->n_barrier_done;
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003088 _rcu_barrier_trace(rsp, "Check", -1, snap_done);
Paul E. McKenney458fb382013-07-26 20:47:42 -07003089
3090 /*
3091 * If the value in snap is odd, we needed to wait for the current
3092 * rcu_barrier() to complete, then wait for the next one, in other
3093 * words, we need the value of snap_done to be three larger than
3094 * the value of snap. On the other hand, if the value in snap is
3095 * even, we only had to wait for the next rcu_barrier() to complete,
3096 * in other words, we need the value of snap_done to be only two
3097 * greater than the value of snap. The "(snap + 3) & ~0x1" computes
3098 * this for us (thank you, Linus!).
3099 */
3100 if (ULONG_CMP_GE(snap_done, (snap + 3) & ~0x1)) {
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003101 _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done);
Paul E. McKenneycf3a9c42012-05-29 14:56:46 -07003102 smp_mb(); /* caller's subsequent code after above check. */
3103 mutex_unlock(&rsp->barrier_mutex);
3104 return;
3105 }
3106
3107 /*
3108 * Increment ->n_barrier_done to avoid duplicate work. Use
3109 * ACCESS_ONCE() to prevent the compiler from speculating
3110 * the increment to precede the early-exit check.
3111 */
3112 ACCESS_ONCE(rsp->n_barrier_done)++;
3113 WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1);
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003114 _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done);
Paul E. McKenneycf3a9c42012-05-29 14:56:46 -07003115 smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003116
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003117 /*
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003118 * Initialize the count to one rather than to zero in order to
3119 * avoid a too-soon return to zero in case of a short grace period
Paul E. McKenney1331e7a2012-08-02 17:43:50 -07003120 * (or preemption of this task). Exclude CPU-hotplug operations
3121 * to ensure that no offline CPU has callbacks queued.
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003122 */
Paul E. McKenney7db74df2012-05-29 03:03:37 -07003123 init_completion(&rsp->barrier_completion);
Paul E. McKenney24ebbca2012-05-29 00:34:56 -07003124 atomic_set(&rsp->barrier_cpu_count, 1);
Paul E. McKenney1331e7a2012-08-02 17:43:50 -07003125 get_online_cpus();
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003126
3127 /*
Paul E. McKenney1331e7a2012-08-02 17:43:50 -07003128 * Force each CPU with callbacks to register a new callback.
3129 * When that callback is invoked, we will know that all of the
3130 * corresponding CPU's preceding callbacks have been invoked.
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003131 */
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003132 for_each_possible_cpu(cpu) {
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01003133 if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu))
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003134 continue;
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003135 rdp = per_cpu_ptr(rsp->rda, cpu);
Frederic Weisbeckerd1e43fa2013-03-26 23:47:24 +01003136 if (rcu_is_nocb_cpu(cpu)) {
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003137 _rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
3138 rsp->n_barrier_done);
3139 atomic_inc(&rsp->barrier_cpu_count);
3140 __call_rcu(&rdp->barrier_head, rcu_barrier_callback,
3141 rsp, cpu, 0);
3142 } else if (ACCESS_ONCE(rdp->qlen)) {
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003143 _rcu_barrier_trace(rsp, "OnlineQ", cpu,
3144 rsp->n_barrier_done);
Paul E. McKenney037b64e2012-05-28 23:26:01 -07003145 smp_call_function_single(cpu, rcu_barrier_func, rsp, 1);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003146 } else {
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003147 _rcu_barrier_trace(rsp, "OnlineNQ", cpu,
3148 rsp->n_barrier_done);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003149 }
3150 }
Paul E. McKenney1331e7a2012-08-02 17:43:50 -07003151 put_online_cpus();
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003152
3153 /*
3154 * Now that we have an rcu_barrier_callback() callback on each
3155 * CPU, and thus each counted, remove the initial count.
3156 */
Paul E. McKenney24ebbca2012-05-29 00:34:56 -07003157 if (atomic_dec_and_test(&rsp->barrier_cpu_count))
Paul E. McKenney7db74df2012-05-29 03:03:37 -07003158 complete(&rsp->barrier_completion);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003159
Paul E. McKenneycf3a9c42012-05-29 14:56:46 -07003160 /* Increment ->n_barrier_done to prevent duplicate work. */
3161 smp_mb(); /* Keep increment after above mechanism. */
3162 ACCESS_ONCE(rsp->n_barrier_done)++;
3163 WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0);
Paul E. McKenneya83eff02012-05-23 18:47:05 -07003164 _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done);
Paul E. McKenneycf3a9c42012-05-29 14:56:46 -07003165 smp_mb(); /* Keep increment before caller's subsequent code. */
3166
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003167 /* Wait for all rcu_barrier_callback() callbacks to be invoked. */
Paul E. McKenney7db74df2012-05-29 03:03:37 -07003168 wait_for_completion(&rsp->barrier_completion);
Paul E. McKenneyb1420f12012-03-01 13:18:08 -08003169
3170 /* Other rcu_barrier() invocations can now safely proceed. */
Paul E. McKenney7be7f0b2012-05-29 05:18:53 -07003171 mutex_unlock(&rsp->barrier_mutex);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003172}
3173
3174/**
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003175 * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
3176 */
3177void rcu_barrier_bh(void)
3178{
Paul E. McKenney037b64e2012-05-28 23:26:01 -07003179 _rcu_barrier(&rcu_bh_state);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003180}
3181EXPORT_SYMBOL_GPL(rcu_barrier_bh);
3182
3183/**
3184 * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
3185 */
3186void rcu_barrier_sched(void)
3187{
Paul E. McKenney037b64e2012-05-28 23:26:01 -07003188 _rcu_barrier(&rcu_sched_state);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003189}
3190EXPORT_SYMBOL_GPL(rcu_barrier_sched);
3191
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003192/*
Paul E. McKenney27569622009-08-15 09:53:46 -07003193 * Do boot-time initialization of a CPU's per-CPU RCU data.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003194 */
Paul E. McKenney27569622009-08-15 09:53:46 -07003195static void __init
3196rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003197{
3198 unsigned long flags;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08003199 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney27569622009-08-15 09:53:46 -07003200 struct rcu_node *rnp = rcu_get_root(rsp);
3201
3202 /* Set up local state, ensuring consistent view of global state. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003203 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney27569622009-08-15 09:53:46 -07003204 rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
Paul E. McKenney3f5d3ea2012-05-09 15:39:56 -07003205 init_callback_list(rdp);
Paul E. McKenney486e2592012-01-06 14:11:30 -08003206 rdp->qlen_lazy = 0;
Paul E. McKenney1d1fb392012-05-09 15:44:42 -07003207 ACCESS_ONCE(rdp->qlen) = 0;
Paul E. McKenney27569622009-08-15 09:53:46 -07003208 rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
Paul E. McKenney29e37d82011-11-17 16:55:56 -08003209 WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
Paul E. McKenney9b2e4f12011-09-30 12:10:22 -07003210 WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
Paul E. McKenney27569622009-08-15 09:53:46 -07003211 rdp->cpu = cpu;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07003212 rdp->rsp = rsp;
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003213 rcu_boot_init_nocb_percpu_data(rdp);
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003214 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney27569622009-08-15 09:53:46 -07003215}
3216
3217/*
3218 * Initialize a CPU's per-CPU RCU data. Note that only one online or
3219 * offline event can be happening at a given time. Note also that we
3220 * can accept some slop in the rsp->completed access due to the fact
3221 * that this CPU cannot possibly have any RCU callbacks in flight yet.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003222 */
Paul Gortmaker49fb4c62013-06-19 14:52:21 -04003223static void
Iulia Manda9b671222014-03-11 13:18:22 +02003224rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003225{
3226 unsigned long flags;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003227 unsigned long mask;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08003228 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003229 struct rcu_node *rnp = rcu_get_root(rsp);
3230
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07003231 /* Exclude new grace periods. */
3232 mutex_lock(&rsp->onoff_mutex);
3233
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003234 /* Set up local state, ensuring consistent view of global state. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003235 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003236 rdp->beenonline = 1; /* We have now been online. */
Paul E. McKenney37c72e52009-10-14 10:15:55 -07003237 rdp->qlen_last_fqs_check = 0;
3238 rdp->n_force_qs_snap = rsp->n_force_qs;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003239 rdp->blimit = blimit;
Paul E. McKenney0d8ee372012-08-03 13:16:15 -07003240 init_callback_list(rdp); /* Re-enable callbacks on this CPU. */
Paul E. McKenney29e37d82011-11-17 16:55:56 -08003241 rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
Paul E. McKenney23332102013-06-21 12:34:33 -07003242 rcu_sysidle_init_percpu_data(rdp->dynticks);
Paul E. McKenneyc92b1312011-11-23 13:38:58 -08003243 atomic_set(&rdp->dynticks->dynticks,
3244 (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003245 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003246
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003247 /* Add CPU to rcu_node bitmasks. */
3248 rnp = rdp->mynode;
3249 mask = rdp->grpmask;
3250 do {
3251 /* Exclude any attempts to start a new GP on small systems. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003252 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003253 rnp->qsmaskinit |= mask;
3254 mask = rnp->grpmask;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08003255 if (rnp == rdp->mynode) {
Paul E. McKenney06ae1152011-08-14 15:56:54 -07003256 /*
3257 * If there is a grace period in progress, we will
3258 * set up to wait for it next time we run the
3259 * RCU core code.
3260 */
3261 rdp->gpnum = rnp->completed;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08003262 rdp->completed = rnp->completed;
Paul E. McKenney06ae1152011-08-14 15:56:54 -07003263 rdp->passed_quiesce = 0;
3264 rdp->qs_pending = 0;
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04003265 trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08003266 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003267 raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003268 rnp = rnp->parent;
3269 } while (rnp != NULL && !(rnp->qsmaskinit & mask));
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07003270 local_irq_restore(flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003271
Paul E. McKenneya4fbe352012-10-07 08:36:12 -07003272 mutex_unlock(&rsp->onoff_mutex);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003273}
3274
Paul Gortmaker49fb4c62013-06-19 14:52:21 -04003275static void rcu_prepare_cpu(int cpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003276{
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07003277 struct rcu_state *rsp;
3278
3279 for_each_rcu_flavor(rsp)
Iulia Manda9b671222014-03-11 13:18:22 +02003280 rcu_init_percpu_data(cpu, rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003281}
3282
3283/*
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07003284 * Handle CPU online/offline notification events.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003285 */
Paul Gortmaker49fb4c62013-06-19 14:52:21 -04003286static int rcu_cpu_notify(struct notifier_block *self,
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08003287 unsigned long action, void *hcpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003288{
3289 long cpu = (long)hcpu;
Paul E. McKenney27f4d282011-02-07 12:47:15 -08003290 struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
Paul E. McKenneya26ac242011-01-12 14:10:23 -08003291 struct rcu_node *rnp = rdp->mynode;
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07003292 struct rcu_state *rsp;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003293
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04003294 trace_rcu_utilization(TPS("Start CPU hotplug"));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003295 switch (action) {
3296 case CPU_UP_PREPARE:
3297 case CPU_UP_PREPARE_FROZEN:
Peter Zijlstrad72bce02011-05-30 13:34:51 +02003298 rcu_prepare_cpu(cpu);
3299 rcu_prepare_kthreads(cpu);
Paul E. McKenneya26ac242011-01-12 14:10:23 -08003300 break;
3301 case CPU_ONLINE:
Paul E. McKenney0f962a52011-04-14 12:13:53 -07003302 case CPU_DOWN_FAILED:
Thomas Gleixner5d01bbd2012-07-16 10:42:35 +00003303 rcu_boost_kthread_setaffinity(rnp, -1);
Paul E. McKenney0f962a52011-04-14 12:13:53 -07003304 break;
3305 case CPU_DOWN_PREPARE:
Paul E. McKenney34ed62462013-01-07 13:37:42 -08003306 rcu_boost_kthread_setaffinity(rnp, cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003307 break;
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003308 case CPU_DYING:
3309 case CPU_DYING_FROZEN:
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07003310 for_each_rcu_flavor(rsp)
3311 rcu_cleanup_dying_cpu(rsp);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07003312 break;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003313 case CPU_DEAD:
3314 case CPU_DEAD_FROZEN:
3315 case CPU_UP_CANCELED:
3316 case CPU_UP_CANCELED_FROZEN:
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07003317 for_each_rcu_flavor(rsp)
3318 rcu_cleanup_dead_cpu(cpu, rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003319 break;
3320 default:
3321 break;
3322 }
Steven Rostedt (Red Hat)f7f7bac2013-07-12 17:18:47 -04003323 trace_rcu_utilization(TPS("End CPU hotplug"));
Paul E. McKenney34ed62462013-01-07 13:37:42 -08003324 return NOTIFY_OK;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003325}
3326
Borislav Petkovd1d74d12013-04-22 00:12:42 +02003327static int rcu_pm_notify(struct notifier_block *self,
3328 unsigned long action, void *hcpu)
3329{
3330 switch (action) {
3331 case PM_HIBERNATION_PREPARE:
3332 case PM_SUSPEND_PREPARE:
3333 if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
3334 rcu_expedited = 1;
3335 break;
3336 case PM_POST_HIBERNATION:
3337 case PM_POST_SUSPEND:
3338 rcu_expedited = 0;
3339 break;
3340 default:
3341 break;
3342 }
3343 return NOTIFY_OK;
3344}
3345
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003346/*
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07003347 * Spawn the kthread that handles this RCU flavor's grace periods.
3348 */
3349static int __init rcu_spawn_gp_kthread(void)
3350{
3351 unsigned long flags;
3352 struct rcu_node *rnp;
3353 struct rcu_state *rsp;
3354 struct task_struct *t;
3355
3356 for_each_rcu_flavor(rsp) {
Kees Cookf1701682013-07-03 15:04:58 -07003357 t = kthread_run(rcu_gp_kthread, rsp, "%s", rsp->name);
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07003358 BUG_ON(IS_ERR(t));
3359 rnp = rcu_get_root(rsp);
3360 raw_spin_lock_irqsave(&rnp->lock, flags);
3361 rsp->gp_kthread = t;
3362 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney3fbfbf72012-08-19 21:35:53 -07003363 rcu_spawn_nocb_kthreads(rsp);
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07003364 }
3365 return 0;
3366}
3367early_initcall(rcu_spawn_gp_kthread);
3368
3369/*
Paul E. McKenneybbad9372010-04-02 16:17:17 -07003370 * This function is invoked towards the end of the scheduler's initialization
3371 * process. Before this is called, the idle task might contain
3372 * RCU read-side critical sections (during which time, this idle
3373 * task is booting the system). After this function is called, the
3374 * idle tasks are prohibited from containing RCU read-side critical
3375 * sections. This function also enables RCU lockdep checking.
3376 */
3377void rcu_scheduler_starting(void)
3378{
3379 WARN_ON(num_online_cpus() != 1);
3380 WARN_ON(nr_context_switches() > 0);
3381 rcu_scheduler_active = 1;
3382}
3383
3384/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003385 * Compute the per-level fanout, either using the exact fanout specified
3386 * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
3387 */
3388#ifdef CONFIG_RCU_FANOUT_EXACT
3389static void __init rcu_init_levelspread(struct rcu_state *rsp)
3390{
3391 int i;
3392
Paul E. McKenney04f34652013-10-16 08:39:10 -07003393 rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
3394 for (i = rcu_num_lvls - 2; i >= 0; i--)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003395 rsp->levelspread[i] = CONFIG_RCU_FANOUT;
3396}
3397#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
3398static void __init rcu_init_levelspread(struct rcu_state *rsp)
3399{
3400 int ccur;
3401 int cprv;
3402 int i;
3403
Paul E. McKenney4dbd6bb2012-09-05 21:43:57 -07003404 cprv = nr_cpu_ids;
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003405 for (i = rcu_num_lvls - 1; i >= 0; i--) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003406 ccur = rsp->levelcnt[i];
3407 rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
3408 cprv = ccur;
3409 }
3410}
3411#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
3412
3413/*
3414 * Helper function for rcu_init() that initializes one rcu_state structure.
3415 */
Lai Jiangshan394f99a2010-06-28 16:25:04 +08003416static void __init rcu_init_one(struct rcu_state *rsp,
3417 struct rcu_data __percpu *rda)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003418{
Paul E. McKenney394f2762012-06-26 17:00:35 -07003419 static char *buf[] = { "rcu_node_0",
3420 "rcu_node_1",
3421 "rcu_node_2",
3422 "rcu_node_3" }; /* Match MAX_RCU_LVLS */
3423 static char *fqs[] = { "rcu_node_fqs_0",
3424 "rcu_node_fqs_1",
3425 "rcu_node_fqs_2",
3426 "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003427 int cpustride = 1;
3428 int i;
3429 int j;
3430 struct rcu_node *rnp;
3431
Paul E. McKenneyb6407e82010-01-04 16:04:02 -08003432 BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
3433
Paul E. McKenney49305212012-11-29 13:49:00 -08003434 /* Silence gcc 4.8 warning about array index out of range. */
3435 if (rcu_num_lvls > RCU_NUM_LVLS)
3436 panic("rcu_init_one: rcu_num_lvls overflow");
3437
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003438 /* Initialize the level-tracking arrays. */
3439
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003440 for (i = 0; i < rcu_num_lvls; i++)
3441 rsp->levelcnt[i] = num_rcu_lvl[i];
3442 for (i = 1; i < rcu_num_lvls; i++)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003443 rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
3444 rcu_init_levelspread(rsp);
3445
3446 /* Initialize the elements themselves, starting from the leaves. */
3447
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003448 for (i = rcu_num_lvls - 1; i >= 0; i--) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003449 cpustride *= rsp->levelspread[i];
3450 rnp = rsp->level[i];
3451 for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08003452 raw_spin_lock_init(&rnp->lock);
Paul E. McKenneyb6407e82010-01-04 16:04:02 -08003453 lockdep_set_class_and_name(&rnp->lock,
3454 &rcu_node_class[i], buf[i]);
Paul E. McKenney394f2762012-06-26 17:00:35 -07003455 raw_spin_lock_init(&rnp->fqslock);
3456 lockdep_set_class_and_name(&rnp->fqslock,
3457 &rcu_fqs_class[i], fqs[i]);
Paul E. McKenney25d30cf2012-07-11 05:23:18 -07003458 rnp->gpnum = rsp->gpnum;
3459 rnp->completed = rsp->completed;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003460 rnp->qsmask = 0;
3461 rnp->qsmaskinit = 0;
3462 rnp->grplo = j * cpustride;
3463 rnp->grphi = (j + 1) * cpustride - 1;
3464 if (rnp->grphi >= NR_CPUS)
3465 rnp->grphi = NR_CPUS - 1;
3466 if (i == 0) {
3467 rnp->grpnum = 0;
3468 rnp->grpmask = 0;
3469 rnp->parent = NULL;
3470 } else {
3471 rnp->grpnum = j % rsp->levelspread[i - 1];
3472 rnp->grpmask = 1UL << rnp->grpnum;
3473 rnp->parent = rsp->level[i - 1] +
3474 j / rsp->levelspread[i - 1];
3475 }
3476 rnp->level = i;
Paul E. McKenney12f5f522010-11-29 21:56:39 -08003477 INIT_LIST_HEAD(&rnp->blkd_tasks);
Paul E. McKenneydae6e642013-02-10 20:48:58 -08003478 rcu_init_one_nocb(rnp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003479 }
3480 }
Lai Jiangshan0c340292010-03-28 11:12:30 +08003481
Lai Jiangshan394f99a2010-06-28 16:25:04 +08003482 rsp->rda = rda;
Paul E. McKenneyb3dbec72012-06-18 18:36:08 -07003483 init_waitqueue_head(&rsp->gp_wq);
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003484 rnp = rsp->level[rcu_num_lvls - 1];
Lai Jiangshan0c340292010-03-28 11:12:30 +08003485 for_each_possible_cpu(i) {
Paul E. McKenney4a90a062010-04-14 16:48:11 -07003486 while (i > rnp->grphi)
Lai Jiangshan0c340292010-03-28 11:12:30 +08003487 rnp++;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08003488 per_cpu_ptr(rsp->rda, i)->mynode = rnp;
Lai Jiangshan0c340292010-03-28 11:12:30 +08003489 rcu_boot_init_percpu_data(i, rsp);
3490 }
Paul E. McKenney6ce75a22012-06-12 11:01:13 -07003491 list_add(&rsp->flavors, &rcu_struct_flavors);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003492}
3493
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003494/*
3495 * Compute the rcu_node tree geometry from kernel parameters. This cannot
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003496 * replace the definitions in tree.h because those are needed to size
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003497 * the ->node array in the rcu_state structure.
3498 */
3499static void __init rcu_init_geometry(void)
3500{
Paul E. McKenney026ad282013-04-03 22:14:11 -07003501 ulong d;
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003502 int i;
3503 int j;
Paul E. McKenneycca6f392012-05-08 21:00:28 -07003504 int n = nr_cpu_ids;
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003505 int rcu_capacity[MAX_RCU_LVLS + 1];
3506
Paul E. McKenney026ad282013-04-03 22:14:11 -07003507 /*
3508 * Initialize any unspecified boot parameters.
3509 * The default values of jiffies_till_first_fqs and
3510 * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS
3511 * value, which is a function of HZ, then adding one for each
3512 * RCU_JIFFIES_FQS_DIV CPUs that might be on the system.
3513 */
3514 d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV;
3515 if (jiffies_till_first_fqs == ULONG_MAX)
3516 jiffies_till_first_fqs = d;
3517 if (jiffies_till_next_fqs == ULONG_MAX)
3518 jiffies_till_next_fqs = d;
3519
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003520 /* If the compile-time values are accurate, just leave. */
Paul E. McKenneyb17c7032012-09-06 15:38:02 -07003521 if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
3522 nr_cpu_ids == NR_CPUS)
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003523 return;
Paul E. McKenney39479092013-10-09 15:20:33 -07003524 pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n",
3525 rcu_fanout_leaf, nr_cpu_ids);
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003526
3527 /*
3528 * Compute number of nodes that can be handled an rcu_node tree
3529 * with the given number of levels. Setting rcu_capacity[0] makes
3530 * some of the arithmetic easier.
3531 */
3532 rcu_capacity[0] = 1;
3533 rcu_capacity[1] = rcu_fanout_leaf;
3534 for (i = 2; i <= MAX_RCU_LVLS; i++)
3535 rcu_capacity[i] = rcu_capacity[i - 1] * CONFIG_RCU_FANOUT;
3536
3537 /*
3538 * The boot-time rcu_fanout_leaf parameter is only permitted
3539 * to increase the leaf-level fanout, not decrease it. Of course,
3540 * the leaf-level fanout cannot exceed the number of bits in
3541 * the rcu_node masks. Finally, the tree must be able to accommodate
3542 * the configured number of CPUs. Complain and fall back to the
3543 * compile-time values if these limits are exceeded.
3544 */
3545 if (rcu_fanout_leaf < CONFIG_RCU_FANOUT_LEAF ||
3546 rcu_fanout_leaf > sizeof(unsigned long) * 8 ||
3547 n > rcu_capacity[MAX_RCU_LVLS]) {
3548 WARN_ON(1);
3549 return;
3550 }
3551
3552 /* Calculate the number of rcu_nodes at each level of the tree. */
3553 for (i = 1; i <= MAX_RCU_LVLS; i++)
3554 if (n <= rcu_capacity[i]) {
3555 for (j = 0; j <= i; j++)
3556 num_rcu_lvl[j] =
3557 DIV_ROUND_UP(n, rcu_capacity[i - j]);
3558 rcu_num_lvls = i;
3559 for (j = i + 1; j <= MAX_RCU_LVLS; j++)
3560 num_rcu_lvl[j] = 0;
3561 break;
3562 }
3563
3564 /* Calculate the total number of rcu_node structures. */
3565 rcu_num_nodes = 0;
3566 for (i = 0; i <= MAX_RCU_LVLS; i++)
3567 rcu_num_nodes += num_rcu_lvl[i];
3568 rcu_num_nodes -= n;
3569}
3570
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08003571void __init rcu_init(void)
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07003572{
Paul E. McKenney017c4262010-01-14 16:10:58 -08003573 int cpu;
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08003574
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07003575 rcu_bootup_announce();
Paul E. McKenneyf885b7f2012-04-23 15:52:53 -07003576 rcu_init_geometry();
Lai Jiangshan394f99a2010-06-28 16:25:04 +08003577 rcu_init_one(&rcu_bh_state, &rcu_bh_data);
Paul E. McKenney69c8d282013-09-03 09:52:20 -07003578 rcu_init_one(&rcu_sched_state, &rcu_sched_data);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07003579 __rcu_init_preempt();
Jiang Fangb5b39362013-02-02 14:13:42 -08003580 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08003581
3582 /*
3583 * We don't need protection against CPU-hotplug here because
3584 * this is called early in boot, before either interrupts
3585 * or the scheduler are operational.
3586 */
3587 cpu_notifier(rcu_cpu_notify, 0);
Borislav Petkovd1d74d12013-04-22 00:12:42 +02003588 pm_notifier(rcu_pm_notify, 0);
Paul E. McKenney017c4262010-01-14 16:10:58 -08003589 for_each_online_cpu(cpu)
3590 rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01003591}
3592
Paul E. McKenney4102ada2013-10-08 20:23:47 -07003593#include "tree_plugin.h"