hid: jarvis: Supress kernel debug prints in atvr_raw_event()
[linux-3.10.git] / kernel / rcutiny.c
1 /*
2  * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
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
15  * along with this program; if not, write to the Free Software
16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17  *
18  * Copyright IBM Corporation, 2008
19  *
20  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
21  *
22  * For detailed explanation of Read-Copy Update mechanism see -
23  *              Documentation/RCU
24  */
25 #include <linux/completion.h>
26 #include <linux/interrupt.h>
27 #include <linux/notifier.h>
28 #include <linux/rcupdate.h>
29 #include <linux/kernel.h>
30 #include <linux/export.h>
31 #include <linux/mutex.h>
32 #include <linux/sched.h>
33 #include <linux/types.h>
34 #include <linux/init.h>
35 #include <linux/time.h>
36 #include <linux/cpu.h>
37 #include <linux/prefetch.h>
38
39 #ifdef CONFIG_RCU_TRACE
40 #include <trace/events/rcu.h>
41 #endif /* #else #ifdef CONFIG_RCU_TRACE */
42
43 #include "rcu.h"
44
45 /* Forward declarations for rcutiny_plugin.h. */
46 struct rcu_ctrlblk;
47 static void invoke_rcu_callbacks(void);
48 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
49 static void rcu_process_callbacks(struct softirq_action *unused);
50 static void __call_rcu(struct rcu_head *head,
51                        void (*func)(struct rcu_head *rcu),
52                        struct rcu_ctrlblk *rcp);
53
54 static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
55
56 #include "rcutiny_plugin.h"
57
58 /* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
59 static void rcu_idle_enter_common(long long newval)
60 {
61         if (newval) {
62                 RCU_TRACE(trace_rcu_dyntick("--=",
63                                             rcu_dynticks_nesting, newval));
64                 rcu_dynticks_nesting = newval;
65                 return;
66         }
67         RCU_TRACE(trace_rcu_dyntick("Start", rcu_dynticks_nesting, newval));
68         if (!is_idle_task(current)) {
69                 struct task_struct *idle = idle_task(smp_processor_id());
70
71                 RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
72                                             rcu_dynticks_nesting, newval));
73                 ftrace_dump(DUMP_ALL);
74                 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
75                           current->pid, current->comm,
76                           idle->pid, idle->comm); /* must be idle task! */
77         }
78         rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
79         barrier();
80         rcu_dynticks_nesting = newval;
81 }
82
83 /*
84  * Enter idle, which is an extended quiescent state if we have fully
85  * entered that mode (i.e., if the new value of dynticks_nesting is zero).
86  */
87 void rcu_idle_enter(void)
88 {
89         unsigned long flags;
90         long long newval;
91
92         local_irq_save(flags);
93         WARN_ON_ONCE((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) == 0);
94         if ((rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK) ==
95             DYNTICK_TASK_NEST_VALUE)
96                 newval = 0;
97         else
98                 newval = rcu_dynticks_nesting - DYNTICK_TASK_NEST_VALUE;
99         rcu_idle_enter_common(newval);
100         local_irq_restore(flags);
101 }
102 EXPORT_SYMBOL_GPL(rcu_idle_enter);
103
104 /*
105  * Exit an interrupt handler towards idle.
106  */
107 void rcu_irq_exit(void)
108 {
109         unsigned long flags;
110         long long newval;
111
112         local_irq_save(flags);
113         newval = rcu_dynticks_nesting - 1;
114         WARN_ON_ONCE(newval < 0);
115         rcu_idle_enter_common(newval);
116         local_irq_restore(flags);
117 }
118 EXPORT_SYMBOL_GPL(rcu_irq_exit);
119
120 /* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
121 static void rcu_idle_exit_common(long long oldval)
122 {
123         if (oldval) {
124                 RCU_TRACE(trace_rcu_dyntick("++=",
125                                             oldval, rcu_dynticks_nesting));
126                 return;
127         }
128         RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
129         if (!is_idle_task(current)) {
130                 struct task_struct *idle = idle_task(smp_processor_id());
131
132                 RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
133                           oldval, rcu_dynticks_nesting));
134                 ftrace_dump(DUMP_ALL);
135                 WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
136                           current->pid, current->comm,
137                           idle->pid, idle->comm); /* must be idle task! */
138         }
139 }
140
141 /*
142  * Exit idle, so that we are no longer in an extended quiescent state.
143  */
144 void rcu_idle_exit(void)
145 {
146         unsigned long flags;
147         long long oldval;
148
149         local_irq_save(flags);
150         oldval = rcu_dynticks_nesting;
151         WARN_ON_ONCE(rcu_dynticks_nesting < 0);
152         if (rcu_dynticks_nesting & DYNTICK_TASK_NEST_MASK)
153                 rcu_dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
154         else
155                 rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
156         rcu_idle_exit_common(oldval);
157         local_irq_restore(flags);
158 }
159 EXPORT_SYMBOL_GPL(rcu_idle_exit);
160
161 /*
162  * Enter an interrupt handler, moving away from idle.
163  */
164 void rcu_irq_enter(void)
165 {
166         unsigned long flags;
167         long long oldval;
168
169         local_irq_save(flags);
170         oldval = rcu_dynticks_nesting;
171         rcu_dynticks_nesting++;
172         WARN_ON_ONCE(rcu_dynticks_nesting == 0);
173         rcu_idle_exit_common(oldval);
174         local_irq_restore(flags);
175 }
176 EXPORT_SYMBOL_GPL(rcu_irq_enter);
177
178 #ifdef CONFIG_DEBUG_LOCK_ALLOC
179
180 /*
181  * Test whether RCU thinks that the current CPU is idle.
182  */
183 int rcu_is_cpu_idle(void)
184 {
185         return !rcu_dynticks_nesting;
186 }
187 EXPORT_SYMBOL(rcu_is_cpu_idle);
188
189 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
190
191 /*
192  * Test whether the current CPU was interrupted from idle.  Nested
193  * interrupts don't count, we must be running at the first interrupt
194  * level.
195  */
196 static int rcu_is_cpu_rrupt_from_idle(void)
197 {
198         return rcu_dynticks_nesting <= 1;
199 }
200
201 /*
202  * Helper function for rcu_sched_qs() and rcu_bh_qs().
203  * Also irqs are disabled to avoid confusion due to interrupt handlers
204  * invoking call_rcu().
205  */
206 static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
207 {
208         reset_cpu_stall_ticks(rcp);
209         if (rcp->rcucblist != NULL &&
210             rcp->donetail != rcp->curtail) {
211                 rcp->donetail = rcp->curtail;
212                 return 1;
213         }
214
215         return 0;
216 }
217
218 /*
219  * Record an rcu quiescent state.  And an rcu_bh quiescent state while we
220  * are at it, given that any rcu quiescent state is also an rcu_bh
221  * quiescent state.  Use "+" instead of "||" to defeat short circuiting.
222  */
223 void rcu_sched_qs(int cpu)
224 {
225         unsigned long flags;
226
227         local_irq_save(flags);
228         if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
229             rcu_qsctr_help(&rcu_bh_ctrlblk))
230                 invoke_rcu_callbacks();
231         local_irq_restore(flags);
232 }
233
234 /*
235  * Record an rcu_bh quiescent state.
236  */
237 void rcu_bh_qs(int cpu)
238 {
239         unsigned long flags;
240
241         local_irq_save(flags);
242         if (rcu_qsctr_help(&rcu_bh_ctrlblk))
243                 invoke_rcu_callbacks();
244         local_irq_restore(flags);
245 }
246
247 /*
248  * Check to see if the scheduling-clock interrupt came from an extended
249  * quiescent state, and, if so, tell RCU about it.  This function must
250  * be called from hardirq context.  It is normally called from the
251  * scheduling-clock interrupt.
252  */
253 void rcu_check_callbacks(int cpu, int user)
254 {
255         check_cpu_stalls();
256         if (user || rcu_is_cpu_rrupt_from_idle())
257                 rcu_sched_qs(cpu);
258         else if (!in_softirq())
259                 rcu_bh_qs(cpu);
260         rcu_preempt_check_callbacks();
261 }
262
263 /*
264  * Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
265  * whose grace period has elapsed.
266  */
267 static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
268 {
269         char *rn = NULL;
270         struct rcu_head *next, *list;
271         unsigned long flags;
272         RCU_TRACE(int cb_count = 0);
273
274         /* If no RCU callbacks ready to invoke, just return. */
275         if (&rcp->rcucblist == rcp->donetail) {
276                 RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1));
277                 RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
278                                               ACCESS_ONCE(rcp->rcucblist),
279                                               need_resched(),
280                                               is_idle_task(current),
281                                               rcu_is_callbacks_kthread()));
282                 return;
283         }
284
285         /* Move the ready-to-invoke callbacks to a local list. */
286         local_irq_save(flags);
287         RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1));
288         list = rcp->rcucblist;
289         rcp->rcucblist = *rcp->donetail;
290         *rcp->donetail = NULL;
291         if (rcp->curtail == rcp->donetail)
292                 rcp->curtail = &rcp->rcucblist;
293         rcu_preempt_remove_callbacks(rcp);
294         rcp->donetail = &rcp->rcucblist;
295         local_irq_restore(flags);
296
297         /* Invoke the callbacks on the local list. */
298         RCU_TRACE(rn = rcp->name);
299         while (list) {
300                 next = list->next;
301                 prefetch(next);
302                 debug_rcu_head_unqueue(list);
303                 local_bh_disable();
304                 __rcu_reclaim(rn, list);
305                 local_bh_enable();
306                 list = next;
307                 RCU_TRACE(cb_count++);
308         }
309         RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
310         RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(),
311                                       is_idle_task(current),
312                                       rcu_is_callbacks_kthread()));
313 }
314
315 static void rcu_process_callbacks(struct softirq_action *unused)
316 {
317         __rcu_process_callbacks(&rcu_sched_ctrlblk);
318         __rcu_process_callbacks(&rcu_bh_ctrlblk);
319         rcu_preempt_process_callbacks();
320 }
321
322 /*
323  * Wait for a grace period to elapse.  But it is illegal to invoke
324  * synchronize_sched() from within an RCU read-side critical section.
325  * Therefore, any legal call to synchronize_sched() is a quiescent
326  * state, and so on a UP system, synchronize_sched() need do nothing.
327  * Ditto for synchronize_rcu_bh().  (But Lai Jiangshan points out the
328  * benefits of doing might_sleep() to reduce latency.)
329  *
330  * Cool, huh?  (Due to Josh Triplett.)
331  *
332  * But we want to make this a static inline later.  The cond_resched()
333  * currently makes this problematic.
334  */
335 void synchronize_sched(void)
336 {
337         rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
338                            !lock_is_held(&rcu_lock_map) &&
339                            !lock_is_held(&rcu_sched_lock_map),
340                            "Illegal synchronize_sched() in RCU read-side critical section");
341         cond_resched();
342 }
343 EXPORT_SYMBOL_GPL(synchronize_sched);
344
345 /*
346  * Helper function for call_rcu() and call_rcu_bh().
347  */
348 static void __call_rcu(struct rcu_head *head,
349                        void (*func)(struct rcu_head *rcu),
350                        struct rcu_ctrlblk *rcp)
351 {
352         unsigned long flags;
353
354         debug_rcu_head_queue(head);
355         head->func = func;
356         head->next = NULL;
357
358         local_irq_save(flags);
359         *rcp->curtail = head;
360         rcp->curtail = &head->next;
361         RCU_TRACE(rcp->qlen++);
362         local_irq_restore(flags);
363 }
364
365 /*
366  * Post an RCU callback to be invoked after the end of an RCU-sched grace
367  * period.  But since we have but one CPU, that would be after any
368  * quiescent state.
369  */
370 void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
371 {
372         __call_rcu(head, func, &rcu_sched_ctrlblk);
373 }
374 EXPORT_SYMBOL_GPL(call_rcu_sched);
375
376 /*
377  * Post an RCU bottom-half callback to be invoked after any subsequent
378  * quiescent state.
379  */
380 void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
381 {
382         __call_rcu(head, func, &rcu_bh_ctrlblk);
383 }
384 EXPORT_SYMBOL_GPL(call_rcu_bh);