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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
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 * 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>
44#include <linux/percpu.h>
45#include <linux/notifier.h>
46#include <linux/cpu.h>
47#include <linux/mutex.h>
48#include <linux/time.h>
Paul E. McKenneybbad9372010-04-02 16:17:17 -070049#include <linux/kernel_stat.h>
Paul E. McKenneya26ac242011-01-12 14:10:23 -080050#include <linux/wait.h>
51#include <linux/kthread.h>
Linus Torvalds268bb0c2011-05-20 12:50:29 -070052#include <linux/prefetch.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010053
Paul E. McKenney9f77da92009-08-22 13:56:45 -070054#include "rcutree.h"
Paul E. McKenney29c00b42011-06-17 15:53:19 -070055#include <trace/events/rcu.h>
56
57#include "rcu.h"
Paul E. McKenney9f77da92009-08-22 13:56:45 -070058
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010059/* Data structures. */
60
Paul E. McKenneyb668c9c2009-11-22 08:53:48 -080061static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
Peter Zijlstra88b91c72009-10-26 10:24:31 -070062
Paul E. McKenney4300aa62010-04-13 16:18:22 -070063#define RCU_STATE_INITIALIZER(structname) { \
Paul E. McKenneye99033c2011-06-21 00:13:44 -070064 .level = { &structname##_state.node[0] }, \
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010065 .levelcnt = { \
66 NUM_RCU_LVL_0, /* root of hierarchy. */ \
67 NUM_RCU_LVL_1, \
68 NUM_RCU_LVL_2, \
Paul E. McKenneycf244dc2009-12-02 12:10:14 -080069 NUM_RCU_LVL_3, \
70 NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010071 }, \
Paul E. McKenney83f5b012009-10-28 08:14:49 -070072 .signaled = RCU_GP_IDLE, \
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010073 .gpnum = -300, \
74 .completed = -300, \
Paul E. McKenneye99033c2011-06-21 00:13:44 -070075 .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \
76 .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.fqslock), \
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010077 .n_force_qs = 0, \
78 .n_force_qs_ngp = 0, \
Paul E. McKenney4300aa62010-04-13 16:18:22 -070079 .name = #structname, \
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010080}
81
Paul E. McKenneye99033c2011-06-21 00:13:44 -070082struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched);
Paul E. McKenneyd6714c22009-08-22 13:56:46 -070083DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010084
Paul E. McKenneye99033c2011-06-21 00:13:44 -070085struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh);
Ingo Molnar6258c4f2009-03-25 16:42:24 +010086DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
Ingo Molnarb1f77b02009-03-13 03:20:49 +010087
Paul E. McKenney27f4d282011-02-07 12:47:15 -080088static struct rcu_state *rcu_state;
89
Paul E. McKenneyb0d30412011-07-10 15:57:35 -070090/*
91 * The rcu_scheduler_active variable transitions from zero to one just
92 * before the first task is spawned. So when this variable is zero, RCU
93 * can assume that there is but one task, allowing RCU to (for example)
94 * optimized synchronize_sched() to a simple barrier(). When this variable
95 * is one, RCU must actually do all the hard work required to detect real
96 * grace periods. This variable is also used to suppress boot-time false
97 * positives from lockdep-RCU error checking.
98 */
Paul E. McKenneybbad9372010-04-02 16:17:17 -070099int rcu_scheduler_active __read_mostly;
100EXPORT_SYMBOL_GPL(rcu_scheduler_active);
101
Paul E. McKenneyb0d30412011-07-10 15:57:35 -0700102/*
103 * The rcu_scheduler_fully_active variable transitions from zero to one
104 * during the early_initcall() processing, which is after the scheduler
105 * is capable of creating new tasks. So RCU processing (for example,
106 * creating tasks for RCU priority boosting) must be delayed until after
107 * rcu_scheduler_fully_active transitions from zero to one. We also
108 * currently delay invocation of any RCU callbacks until after this point.
109 *
110 * It might later prove better for people registering RCU callbacks during
111 * early boot to take responsibility for these callbacks, but one step at
112 * a time.
113 */
114static int rcu_scheduler_fully_active __read_mostly;
115
Paul E. McKenneya46e0892011-06-15 15:47:09 -0700116#ifdef CONFIG_RCU_BOOST
117
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100118/*
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800119 * Control variables for per-CPU and per-rcu_node kthreads. These
120 * handle all flavors of RCU.
121 */
122static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
Paul E. McKenneyd71df902011-03-29 17:48:28 -0700123DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
Paul E. McKenney15ba0ba2011-04-06 16:01:16 -0700124DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
Paul E. McKenney5ece5ba2011-04-22 18:08:51 -0700125DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
Paul E. McKenneyd71df902011-03-29 17:48:28 -0700126DEFINE_PER_CPU(char, rcu_cpu_has_work);
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800127
Paul E. McKenneya46e0892011-06-15 15:47:09 -0700128#endif /* #ifdef CONFIG_RCU_BOOST */
129
Paul E. McKenney0f962a52011-04-14 12:13:53 -0700130static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
Paul E. McKenneya46e0892011-06-15 15:47:09 -0700131static void invoke_rcu_core(void);
132static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800133
Paul E. McKenneya26ac242011-01-12 14:10:23 -0800134/*
Paul E. McKenney4a298652011-04-03 21:33:51 -0700135 * Track the rcutorture test sequence number and the update version
136 * number within a given test. The rcutorture_testseq is incremented
137 * on every rcutorture module load and unload, so has an odd value
138 * when a test is running. The rcutorture_vernum is set to zero
139 * when rcutorture starts and is incremented on each rcutorture update.
140 * These variables enable correlating rcutorture output with the
141 * RCU tracing information.
142 */
143unsigned long rcutorture_testseq;
144unsigned long rcutorture_vernum;
145
146/*
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700147 * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
148 * permit this function to be invoked without holding the root rcu_node
149 * structure's ->lock, but of course results can be subject to change.
150 */
151static int rcu_gp_in_progress(struct rcu_state *rsp)
152{
153 return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
154}
155
156/*
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700157 * Note a quiescent state. Because we do not need to know
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100158 * how many quiescent states passed, just if there was at least
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700159 * one since the start of the grace period, this just sets a flag.
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700160 * The caller must have disabled preemption.
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100161 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700162void rcu_sched_qs(int cpu)
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100163{
Paul E. McKenney25502a62010-04-01 17:37:01 -0700164 struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700165
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700166 rdp->passed_quiesce_gpnum = rdp->gpnum;
Paul E. McKenneyc3422be2009-09-13 09:15:10 -0700167 barrier();
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700168 if (rdp->passed_quiesce == 0)
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700169 trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700170 rdp->passed_quiesce = 1;
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100171}
172
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700173void rcu_bh_qs(int cpu)
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100174{
Paul E. McKenney25502a62010-04-01 17:37:01 -0700175 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700176
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700177 rdp->passed_quiesce_gpnum = rdp->gpnum;
Paul E. McKenneyc3422be2009-09-13 09:15:10 -0700178 barrier();
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700179 if (rdp->passed_quiesce == 0)
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700180 trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700181 rdp->passed_quiesce = 1;
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100182}
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100183
Paul E. McKenney25502a62010-04-01 17:37:01 -0700184/*
185 * Note a context switch. This is a quiescent state for RCU-sched,
186 * and requires special handling for preemptible RCU.
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700187 * The caller must have disabled preemption.
Paul E. McKenney25502a62010-04-01 17:37:01 -0700188 */
189void rcu_note_context_switch(int cpu)
190{
Paul E. McKenney300df912011-06-18 22:26:31 -0700191 trace_rcu_utilization("Start context switch");
Paul E. McKenney25502a62010-04-01 17:37:01 -0700192 rcu_sched_qs(cpu);
193 rcu_preempt_note_context_switch(cpu);
Paul E. McKenney300df912011-06-18 22:26:31 -0700194 trace_rcu_utilization("End context switch");
Paul E. McKenney25502a62010-04-01 17:37:01 -0700195}
Gleb Natapov29ce8312011-05-04 16:31:03 +0300196EXPORT_SYMBOL_GPL(rcu_note_context_switch);
Paul E. McKenney25502a62010-04-01 17:37:01 -0700197
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100198#ifdef CONFIG_NO_HZ
Paul E. McKenney90a4d2c2009-01-04 11:41:11 -0800199DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
200 .dynticks_nesting = 1,
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700201 .dynticks = ATOMIC_INIT(1),
Paul E. McKenney90a4d2c2009-01-04 11:41:11 -0800202};
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100203#endif /* #ifdef CONFIG_NO_HZ */
204
Paul E. McKenneye0f23062011-06-21 01:29:39 -0700205static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100206static int qhimark = 10000; /* If this many pending, ignore blimit. */
207static int qlowmark = 100; /* Once only this many pending, use blimit. */
208
Paul E. McKenney3d76c082009-09-28 07:46:32 -0700209module_param(blimit, int, 0);
210module_param(qhimark, int, 0);
211module_param(qlowmark, int, 0);
212
Paul E. McKenneya00e0d712011-02-08 17:14:39 -0800213int rcu_cpu_stall_suppress __read_mostly;
Paul E. McKenneyf2e0dd72010-07-14 14:38:30 -0700214module_param(rcu_cpu_stall_suppress, int, 0644);
Paul E. McKenney742734e2010-06-30 11:43:52 -0700215
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100216static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
Paul E. McKenneya1572292009-08-22 13:56:51 -0700217static int rcu_pending(int cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100218
219/*
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700220 * Return the number of RCU-sched batches processed thus far for debug & stats.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100221 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700222long rcu_batches_completed_sched(void)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100223{
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700224 return rcu_sched_state.completed;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100225}
Paul E. McKenneyd6714c22009-08-22 13:56:46 -0700226EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100227
228/*
229 * Return the number of RCU BH batches processed thus far for debug & stats.
230 */
231long rcu_batches_completed_bh(void)
232{
233 return rcu_bh_state.completed;
234}
235EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
236
237/*
Paul E. McKenneybf66f182010-01-04 15:09:10 -0800238 * Force a quiescent state for RCU BH.
239 */
240void rcu_bh_force_quiescent_state(void)
241{
242 force_quiescent_state(&rcu_bh_state, 0);
243}
244EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
245
246/*
Paul E. McKenney4a298652011-04-03 21:33:51 -0700247 * Record the number of times rcutorture tests have been initiated and
248 * terminated. This information allows the debugfs tracing stats to be
249 * correlated to the rcutorture messages, even when the rcutorture module
250 * is being repeatedly loaded and unloaded. In other words, we cannot
251 * store this state in rcutorture itself.
252 */
253void rcutorture_record_test_transition(void)
254{
255 rcutorture_testseq++;
256 rcutorture_vernum = 0;
257}
258EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
259
260/*
261 * Record the number of writer passes through the current rcutorture test.
262 * This is also used to correlate debugfs tracing stats with the rcutorture
263 * messages.
264 */
265void rcutorture_record_progress(unsigned long vernum)
266{
267 rcutorture_vernum++;
268}
269EXPORT_SYMBOL_GPL(rcutorture_record_progress);
270
271/*
Paul E. McKenneybf66f182010-01-04 15:09:10 -0800272 * Force a quiescent state for RCU-sched.
273 */
274void rcu_sched_force_quiescent_state(void)
275{
276 force_quiescent_state(&rcu_sched_state, 0);
277}
278EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
279
280/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100281 * Does the CPU have callbacks ready to be invoked?
282 */
283static int
284cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
285{
286 return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL];
287}
288
289/*
290 * Does the current CPU require a yet-as-unscheduled grace period?
291 */
292static int
293cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
294{
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700295 return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100296}
297
298/*
299 * Return the root node of the specified rcu_state structure.
300 */
301static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
302{
303 return &rsp->node[0];
304}
305
306#ifdef CONFIG_SMP
307
308/*
309 * If the specified CPU is offline, tell the caller that it is in
310 * a quiescent state. Otherwise, whack it with a reschedule IPI.
311 * Grace periods can end up waiting on an offline CPU when that
312 * CPU is in the process of coming online -- it will be added to the
313 * rcu_node bitmasks before it actually makes it online. The same thing
314 * can happen while a CPU is in the process of coming online. Because this
315 * race is quite rare, we check for it after detecting that the grace
316 * period has been delayed rather than checking each and every CPU
317 * each and every time we start a new grace period.
318 */
319static int rcu_implicit_offline_qs(struct rcu_data *rdp)
320{
321 /*
322 * If the CPU is offline, it is in a quiescent state. We can
323 * trust its state not to change because interrupts are disabled.
324 */
325 if (cpu_is_offline(rdp->cpu)) {
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700326 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100327 rdp->offline_fqs++;
328 return 1;
329 }
330
Paul E. McKenney6cc68792011-03-02 13:15:15 -0800331 /* If preemptible RCU, no point in sending reschedule IPI. */
332 if (rdp->preemptible)
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700333 return 0;
334
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100335 /* The CPU is online, so send it a reschedule IPI. */
336 if (rdp->cpu != smp_processor_id())
337 smp_send_reschedule(rdp->cpu);
338 else
339 set_need_resched();
340 rdp->resched_ipi++;
341 return 0;
342}
343
344#endif /* #ifdef CONFIG_SMP */
345
346#ifdef CONFIG_NO_HZ
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100347
348/**
349 * rcu_enter_nohz - inform RCU that current CPU is entering nohz
350 *
351 * Enter nohz mode, in other words, -leave- the mode in which RCU
352 * read-side critical sections can occur. (Though RCU read-side
353 * critical sections can occur in irq handlers in nohz mode, a possibility
354 * handled by rcu_irq_enter() and rcu_irq_exit()).
355 */
356void rcu_enter_nohz(void)
357{
358 unsigned long flags;
359 struct rcu_dynticks *rdtp;
360
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100361 local_irq_save(flags);
362 rdtp = &__get_cpu_var(rcu_dynticks);
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700363 if (--rdtp->dynticks_nesting) {
364 local_irq_restore(flags);
365 return;
366 }
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700367 trace_rcu_dyntick("Start");
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700368 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
369 smp_mb__before_atomic_inc(); /* See above. */
370 atomic_inc(&rdtp->dynticks);
371 smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
372 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100373 local_irq_restore(flags);
374}
375
376/*
377 * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
378 *
379 * Exit nohz mode, in other words, -enter- the mode in which RCU
380 * read-side critical sections normally occur.
381 */
382void rcu_exit_nohz(void)
383{
384 unsigned long flags;
385 struct rcu_dynticks *rdtp;
386
387 local_irq_save(flags);
388 rdtp = &__get_cpu_var(rcu_dynticks);
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700389 if (rdtp->dynticks_nesting++) {
390 local_irq_restore(flags);
391 return;
392 }
393 smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
394 atomic_inc(&rdtp->dynticks);
395 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
396 smp_mb__after_atomic_inc(); /* See above. */
397 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700398 trace_rcu_dyntick("End");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100399 local_irq_restore(flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100400}
401
402/**
403 * rcu_nmi_enter - inform RCU of entry to NMI context
404 *
405 * If the CPU was idle with dynamic ticks active, and there is no
406 * irq handler running, this updates rdtp->dynticks_nmi to let the
407 * RCU grace-period handling know that the CPU is active.
408 */
409void rcu_nmi_enter(void)
410{
411 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
412
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700413 if (rdtp->dynticks_nmi_nesting == 0 &&
414 (atomic_read(&rdtp->dynticks) & 0x1))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100415 return;
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700416 rdtp->dynticks_nmi_nesting++;
417 smp_mb__before_atomic_inc(); /* Force delay from prior write. */
418 atomic_inc(&rdtp->dynticks);
419 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
420 smp_mb__after_atomic_inc(); /* See above. */
421 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100422}
423
424/**
425 * rcu_nmi_exit - inform RCU of exit from NMI context
426 *
427 * If the CPU was idle with dynamic ticks active, and there is no
428 * irq handler running, this updates rdtp->dynticks_nmi to let the
429 * RCU grace-period handling know that the CPU is no longer active.
430 */
431void rcu_nmi_exit(void)
432{
433 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
434
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700435 if (rdtp->dynticks_nmi_nesting == 0 ||
436 --rdtp->dynticks_nmi_nesting != 0)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100437 return;
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700438 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
439 smp_mb__before_atomic_inc(); /* See above. */
440 atomic_inc(&rdtp->dynticks);
441 smp_mb__after_atomic_inc(); /* Force delay to next write. */
442 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100443}
444
445/**
446 * rcu_irq_enter - inform RCU of entry to hard irq context
447 *
448 * If the CPU was idle with dynamic ticks active, this updates the
449 * rdtp->dynticks to let the RCU handling know that the CPU is active.
450 */
451void rcu_irq_enter(void)
452{
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700453 rcu_exit_nohz();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100454}
455
456/**
457 * rcu_irq_exit - inform RCU of exit from hard irq context
458 *
459 * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
460 * to put let the RCU handling be aware that the CPU is going back to idle
461 * with no ticks.
462 */
463void rcu_irq_exit(void)
464{
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700465 rcu_enter_nohz();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100466}
467
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100468#ifdef CONFIG_SMP
469
470/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100471 * Snapshot the specified CPU's dynticks counter so that we can later
472 * credit them with an implicit quiescent state. Return 1 if this CPU
Paul E. McKenney1eba8f82009-09-23 09:50:42 -0700473 * is in dynticks idle mode, which is an extended quiescent state.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100474 */
475static int dyntick_save_progress_counter(struct rcu_data *rdp)
476{
Paul E. McKenney23b5c8f2010-09-07 10:38:22 -0700477 rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
478 return 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100479}
480
481/*
482 * Return true if the specified CPU has passed through a quiescent
483 * state by virtue of being in or having passed through an dynticks
484 * idle state since the last call to dyntick_save_progress_counter()
485 * for this same CPU.
486 */
487static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
488{
Paul E. McKenney7eb4f452011-07-30 07:32:48 -0700489 unsigned int curr;
490 unsigned int snap;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100491
Paul E. McKenney7eb4f452011-07-30 07:32:48 -0700492 curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
493 snap = (unsigned int)rdp->dynticks_snap;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100494
495 /*
496 * If the CPU passed through or entered a dynticks idle phase with
497 * no active irq/NMI handlers, then we can safely pretend that the CPU
498 * already acknowledged the request to pass through a quiescent
499 * state. Either way, that CPU cannot possibly be in an RCU
500 * read-side critical section that started before the beginning
501 * of the current RCU grace period.
502 */
Paul E. McKenney7eb4f452011-07-30 07:32:48 -0700503 if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700504 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100505 rdp->dynticks_fqs++;
506 return 1;
507 }
508
509 /* Go check for the CPU being offline. */
510 return rcu_implicit_offline_qs(rdp);
511}
512
513#endif /* #ifdef CONFIG_SMP */
514
515#else /* #ifdef CONFIG_NO_HZ */
516
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100517#ifdef CONFIG_SMP
518
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100519static int dyntick_save_progress_counter(struct rcu_data *rdp)
520{
521 return 0;
522}
523
524static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
525{
526 return rcu_implicit_offline_qs(rdp);
527}
528
529#endif /* #ifdef CONFIG_SMP */
530
531#endif /* #else #ifdef CONFIG_NO_HZ */
532
Paul E. McKenney742734e2010-06-30 11:43:52 -0700533int rcu_cpu_stall_suppress __read_mostly;
Paul E. McKenneyc68de202010-04-15 10:12:40 -0700534
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100535static void record_gp_stall_check_time(struct rcu_state *rsp)
536{
537 rsp->gp_start = jiffies;
538 rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
539}
540
541static void print_other_cpu_stall(struct rcu_state *rsp)
542{
543 int cpu;
544 long delta;
545 unsigned long flags;
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700546 int ndetected;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100547 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100548
549 /* Only let one CPU complain about others per time interval. */
550
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800551 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100552 delta = jiffies - rsp->jiffies_stall;
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700553 if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800554 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100555 return;
556 }
557 rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700558
559 /*
560 * Now rat on any tasks that got kicked up to the root rcu_node
561 * due to CPU offlining.
562 */
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700563 ndetected = rcu_print_task_stall(rnp);
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800564 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100565
Paul E. McKenney8cdd32a2010-08-09 14:23:03 -0700566 /*
567 * OK, time to rat on our buddy...
568 * See Documentation/RCU/stallwarn.txt for info on how to debug
569 * RCU CPU stall warnings.
570 */
Paul E. McKenney4300aa62010-04-13 16:18:22 -0700571 printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {",
572 rsp->name);
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700573 rcu_for_each_leaf_node(rsp, rnp) {
Paul E. McKenney3acd9eb2010-02-22 17:05:03 -0800574 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700575 ndetected += rcu_print_task_stall(rnp);
Paul E. McKenney3acd9eb2010-02-22 17:05:03 -0800576 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700577 if (rnp->qsmask == 0)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100578 continue;
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700579 for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700580 if (rnp->qsmask & (1UL << cpu)) {
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700581 printk(" %d", rnp->grplo + cpu);
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700582 ndetected++;
583 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100584 }
Paul E. McKenney4300aa62010-04-13 16:18:22 -0700585 printk("} (detected by %d, t=%ld jiffies)\n",
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100586 smp_processor_id(), (long)(jiffies - rsp->gp_start));
Paul E. McKenney9bc8b552011-08-13 13:31:47 -0700587 if (ndetected == 0)
588 printk(KERN_ERR "INFO: Stall ended before state dump start\n");
589 else if (!trigger_all_cpu_backtrace())
Paul E. McKenney4627e242011-08-03 03:34:24 -0700590 dump_stack();
Ingo Molnarc1dc0b92009-08-02 11:28:21 +0200591
Paul E. McKenney1ed509a2010-02-22 17:05:05 -0800592 /* If so configured, complain about tasks blocking the grace period. */
593
594 rcu_print_detail_task_stall(rsp);
595
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100596 force_quiescent_state(rsp, 0); /* Kick them all. */
597}
598
599static void print_cpu_stall(struct rcu_state *rsp)
600{
601 unsigned long flags;
602 struct rcu_node *rnp = rcu_get_root(rsp);
603
Paul E. McKenney8cdd32a2010-08-09 14:23:03 -0700604 /*
605 * OK, time to rat on ourselves...
606 * See Documentation/RCU/stallwarn.txt for info on how to debug
607 * RCU CPU stall warnings.
608 */
Paul E. McKenney4300aa62010-04-13 16:18:22 -0700609 printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n",
610 rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
Paul E. McKenney4627e242011-08-03 03:34:24 -0700611 if (!trigger_all_cpu_backtrace())
612 dump_stack();
Ingo Molnarc1dc0b92009-08-02 11:28:21 +0200613
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800614 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney20133cf2010-02-22 17:05:01 -0800615 if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100616 rsp->jiffies_stall =
617 jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800618 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Ingo Molnarc1dc0b92009-08-02 11:28:21 +0200619
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100620 set_need_resched(); /* kick ourselves to get things going. */
621}
622
623static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
624{
Paul E. McKenneybad6e132011-05-02 23:40:04 -0700625 unsigned long j;
626 unsigned long js;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100627 struct rcu_node *rnp;
628
Paul E. McKenney742734e2010-06-30 11:43:52 -0700629 if (rcu_cpu_stall_suppress)
Paul E. McKenneyc68de202010-04-15 10:12:40 -0700630 return;
Paul E. McKenneybad6e132011-05-02 23:40:04 -0700631 j = ACCESS_ONCE(jiffies);
632 js = ACCESS_ONCE(rsp->jiffies_stall);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100633 rnp = rdp->mynode;
Paul E. McKenneybad6e132011-05-02 23:40:04 -0700634 if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100635
636 /* We haven't checked in, so go dump stack. */
637 print_cpu_stall(rsp);
638
Paul E. McKenneybad6e132011-05-02 23:40:04 -0700639 } else if (rcu_gp_in_progress(rsp) &&
640 ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100641
Paul E. McKenneybad6e132011-05-02 23:40:04 -0700642 /* They had a few time units to dump stack, so complain. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100643 print_other_cpu_stall(rsp);
644 }
645}
646
Paul E. McKenneyc68de202010-04-15 10:12:40 -0700647static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
648{
Paul E. McKenney742734e2010-06-30 11:43:52 -0700649 rcu_cpu_stall_suppress = 1;
Paul E. McKenneyc68de202010-04-15 10:12:40 -0700650 return NOTIFY_DONE;
651}
652
Paul E. McKenney53d84e02010-08-10 14:28:53 -0700653/**
654 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
655 *
656 * Set the stall-warning timeout way off into the future, thus preventing
657 * any RCU CPU stall-warning messages from appearing in the current set of
658 * RCU grace periods.
659 *
660 * The caller must disable hard irqs.
661 */
662void rcu_cpu_stall_reset(void)
663{
664 rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
665 rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
666 rcu_preempt_stall_reset();
667}
668
Paul E. McKenneyc68de202010-04-15 10:12:40 -0700669static struct notifier_block rcu_panic_block = {
670 .notifier_call = rcu_panic,
671};
672
673static void __init check_cpu_stall_init(void)
674{
675 atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
676}
677
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100678/*
679 * Update CPU-local rcu_data state to record the newly noticed grace period.
680 * This is used both when we started the grace period and when we notice
Paul E. McKenney91603062009-11-02 13:52:29 -0800681 * that someone else started the grace period. The caller must hold the
682 * ->lock of the leaf rcu_node structure corresponding to the current CPU,
683 * and must have irqs disabled.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100684 */
Paul E. McKenney91603062009-11-02 13:52:29 -0800685static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
686{
687 if (rdp->gpnum != rnp->gpnum) {
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800688 /*
689 * If the current grace period is waiting for this CPU,
690 * set up to detect a quiescent state, otherwise don't
691 * go looking for one.
692 */
Paul E. McKenney91603062009-11-02 13:52:29 -0800693 rdp->gpnum = rnp->gpnum;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700694 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800695 if (rnp->qsmask & rdp->grpmask) {
696 rdp->qs_pending = 1;
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -0700697 rdp->passed_quiesce = 0;
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800698 } else
699 rdp->qs_pending = 0;
Paul E. McKenney91603062009-11-02 13:52:29 -0800700 }
701}
702
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100703static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
704{
Paul E. McKenney91603062009-11-02 13:52:29 -0800705 unsigned long flags;
706 struct rcu_node *rnp;
707
708 local_irq_save(flags);
709 rnp = rdp->mynode;
710 if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800711 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
Paul E. McKenney91603062009-11-02 13:52:29 -0800712 local_irq_restore(flags);
713 return;
714 }
715 __note_new_gpnum(rsp, rnp, rdp);
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800716 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100717}
718
719/*
720 * Did someone else start a new RCU grace period start since we last
721 * checked? Update local state appropriately if so. Must be called
722 * on the CPU corresponding to rdp.
723 */
724static int
725check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
726{
727 unsigned long flags;
728 int ret = 0;
729
730 local_irq_save(flags);
731 if (rdp->gpnum != rsp->gpnum) {
732 note_new_gpnum(rsp, rdp);
733 ret = 1;
734 }
735 local_irq_restore(flags);
736 return ret;
737}
738
739/*
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800740 * Advance this CPU's callbacks, but only if the current grace period
741 * has ended. This may be called only from the CPU to whom the rdp
742 * belongs. In addition, the corresponding leaf rcu_node structure's
743 * ->lock must be held by the caller, with irqs disabled.
744 */
745static void
746__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
747{
748 /* Did another grace period end? */
749 if (rdp->completed != rnp->completed) {
750
751 /* Advance callbacks. No harm if list empty. */
752 rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
753 rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
754 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
755
756 /* Remember that we saw this grace-period completion. */
757 rdp->completed = rnp->completed;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700758 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
Frederic Weisbecker20377f32010-12-10 22:11:10 +0100759
760 /*
Frederic Weisbecker5ff8e6f2010-12-10 22:11:11 +0100761 * If we were in an extended quiescent state, we may have
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800762 * missed some grace periods that others CPUs handled on
Frederic Weisbecker5ff8e6f2010-12-10 22:11:11 +0100763 * our behalf. Catch up with this state to avoid noting
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800764 * spurious new grace periods. If another grace period
765 * has started, then rnp->gpnum will have advanced, so
766 * we will detect this later on.
Frederic Weisbecker5ff8e6f2010-12-10 22:11:11 +0100767 */
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800768 if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
Frederic Weisbecker5ff8e6f2010-12-10 22:11:11 +0100769 rdp->gpnum = rdp->completed;
770
771 /*
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800772 * If RCU does not need a quiescent state from this CPU,
773 * then make sure that this CPU doesn't go looking for one.
Frederic Weisbecker20377f32010-12-10 22:11:10 +0100774 */
Paul E. McKenney121dfc42010-12-10 15:02:47 -0800775 if ((rnp->qsmask & rdp->grpmask) == 0)
Frederic Weisbecker20377f32010-12-10 22:11:10 +0100776 rdp->qs_pending = 0;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800777 }
778}
779
780/*
781 * Advance this CPU's callbacks, but only if the current grace period
782 * has ended. This may be called only from the CPU to whom the rdp
783 * belongs.
784 */
785static void
786rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
787{
788 unsigned long flags;
789 struct rcu_node *rnp;
790
791 local_irq_save(flags);
792 rnp = rdp->mynode;
793 if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800794 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800795 local_irq_restore(flags);
796 return;
797 }
798 __rcu_process_gp_end(rsp, rnp, rdp);
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800799 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800800}
801
802/*
803 * Do per-CPU grace-period initialization for running CPU. The caller
804 * must hold the lock of the leaf rcu_node structure corresponding to
805 * this CPU.
806 */
807static void
808rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
809{
810 /* Prior grace period ended, so advance callbacks for current CPU. */
811 __rcu_process_gp_end(rsp, rnp, rdp);
812
813 /*
814 * Because this CPU just now started the new grace period, we know
815 * that all of its callbacks will be covered by this upcoming grace
816 * period, even the ones that were registered arbitrarily recently.
817 * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
818 *
819 * Other CPUs cannot be sure exactly when the grace period started.
820 * Therefore, their recently registered callbacks must pass through
821 * an additional RCU_NEXT_READY stage, so that they will be handled
822 * by the next RCU grace period.
823 */
824 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
825 rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
Paul E. McKenney91603062009-11-02 13:52:29 -0800826
827 /* Set state so that this CPU will detect the next quiescent state. */
828 __note_new_gpnum(rsp, rnp, rdp);
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800829}
830
831/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100832 * Start a new RCU grace period if warranted, re-initializing the hierarchy
833 * in preparation for detecting the next grace period. The caller must hold
834 * the root node's ->lock, which is released before return. Hard irqs must
835 * be disabled.
836 */
837static void
838rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
839 __releases(rcu_get_root(rsp)->lock)
840{
Lai Jiangshan394f99a2010-06-28 16:25:04 +0800841 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100842 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100843
Paul E. McKenney037067a2011-08-07 20:26:31 -0700844 if (!rcu_scheduler_fully_active ||
Paul E. McKenneyafe24b12011-08-24 16:52:09 -0700845 !cpu_needs_another_gp(rsp, rdp)) {
Paul E. McKenneyb32e9eb2009-11-12 22:35:03 -0800846 /*
Paul E. McKenneyafe24b12011-08-24 16:52:09 -0700847 * Either the scheduler hasn't yet spawned the first
848 * non-idle task or this CPU does not need another
849 * grace period. Either way, don't start a new grace
850 * period.
Paul E. McKenneyb32e9eb2009-11-12 22:35:03 -0800851 */
Paul E. McKenneyafe24b12011-08-24 16:52:09 -0700852 raw_spin_unlock_irqrestore(&rnp->lock, flags);
853 return;
854 }
855
856 if (rsp->fqs_active) {
857 /*
858 * This CPU needs a grace period, but force_quiescent_state()
859 * is running. Tell it to start one on this CPU's behalf.
860 */
861 rsp->fqs_need_gp = 1;
862 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100863 return;
864 }
865
866 /* Advance to a new grace period and initialize state. */
867 rsp->gpnum++;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700868 trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
Paul E. McKenneyc3422be2009-09-13 09:15:10 -0700869 WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100870 rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
871 rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100872 record_gp_stall_check_time(rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100873
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100874 /* Special-case the common single-level case. */
875 if (NUM_RCU_NODES == 1) {
Paul E. McKenneyb0e165c2009-09-13 09:15:09 -0700876 rcu_preempt_check_blocked_tasks(rnp);
Paul E. McKenney28ecd582009-09-18 09:50:17 -0700877 rnp->qsmask = rnp->qsmaskinit;
Paul E. McKenneyde078d82009-09-08 15:54:36 -0700878 rnp->gpnum = rsp->gpnum;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800879 rnp->completed = rsp->completed;
Paul E. McKenneyc12172c2009-01-04 20:30:06 -0800880 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800881 rcu_start_gp_per_cpu(rsp, rnp, rdp);
Paul E. McKenney27f4d282011-02-07 12:47:15 -0800882 rcu_preempt_boost_start_gp(rnp);
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700883 trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
884 rnp->level, rnp->grplo,
885 rnp->grphi, rnp->qsmask);
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800886 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100887 return;
888 }
889
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800890 raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100891
892
893 /* Exclude any concurrent CPU-hotplug operations. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800894 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100895
896 /*
Paul E. McKenneyb835db12009-09-08 15:54:37 -0700897 * Set the quiescent-state-needed bits in all the rcu_node
898 * structures for all currently online CPUs in breadth-first
899 * order, starting from the root rcu_node structure. This
900 * operation relies on the layout of the hierarchy within the
901 * rsp->node[] array. Note that other CPUs will access only
902 * the leaves of the hierarchy, which still indicate that no
903 * grace period is in progress, at least until the corresponding
904 * leaf node has been initialized. In addition, we have excluded
905 * CPU-hotplug operations.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100906 *
907 * Note that the grace period cannot complete until we finish
908 * the initialization process, as there will be at least one
909 * qsmask bit set in the root node until that time, namely the
Paul E. McKenneyb835db12009-09-08 15:54:37 -0700910 * one corresponding to this CPU, due to the fact that we have
911 * irqs disabled.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100912 */
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -0700913 rcu_for_each_node_breadth_first(rsp, rnp) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800914 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenneyb0e165c2009-09-13 09:15:09 -0700915 rcu_preempt_check_blocked_tasks(rnp);
Paul E. McKenney49e29122009-09-18 09:50:19 -0700916 rnp->qsmask = rnp->qsmaskinit;
Paul E. McKenneyde078d82009-09-08 15:54:36 -0700917 rnp->gpnum = rsp->gpnum;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -0800918 rnp->completed = rsp->completed;
919 if (rnp == rdp->mynode)
920 rcu_start_gp_per_cpu(rsp, rnp, rdp);
Paul E. McKenney27f4d282011-02-07 12:47:15 -0800921 rcu_preempt_boost_start_gp(rnp);
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700922 trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
923 rnp->level, rnp->grplo,
924 rnp->grphi, rnp->qsmask);
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800925 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100926 }
927
Paul E. McKenney83f5b012009-10-28 08:14:49 -0700928 rnp = rcu_get_root(rsp);
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800929 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100930 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -0800931 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
932 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100933}
934
935/*
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -0800936 * Report a full set of quiescent states to the specified rcu_state
937 * data structure. This involves cleaning up after the prior grace
938 * period and letting rcu_start_gp() start up the next grace period
939 * if one is needed. Note that the caller must hold rnp->lock, as
940 * required by rcu_start_gp(), which will release it.
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700941 */
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -0800942static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700943 __releases(rcu_get_root(rsp)->lock)
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700944{
Paul E. McKenney15ba0ba2011-04-06 16:01:16 -0700945 unsigned long gp_duration;
Paul E. McKenneyafe24b12011-08-24 16:52:09 -0700946 struct rcu_node *rnp = rcu_get_root(rsp);
947 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
Paul E. McKenney15ba0ba2011-04-06 16:01:16 -0700948
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -0700949 WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
Paul E. McKenney0bbcc522011-05-16 02:24:04 -0700950
951 /*
952 * Ensure that all grace-period and pre-grace-period activity
953 * is seen before the assignment to rsp->completed.
954 */
955 smp_mb(); /* See above block comment. */
Paul E. McKenney15ba0ba2011-04-06 16:01:16 -0700956 gp_duration = jiffies - rsp->gp_start;
957 if (gp_duration > rsp->gp_max)
958 rsp->gp_max = gp_duration;
Paul E. McKenneyafe24b12011-08-24 16:52:09 -0700959
960 /*
961 * We know the grace period is complete, but to everyone else
962 * it appears to still be ongoing. But it is also the case
963 * that to everyone else it looks like there is nothing that
964 * they can do to advance the grace period. It is therefore
965 * safe for us to drop the lock in order to mark the grace
966 * period as completed in all of the rcu_node structures.
967 *
968 * But if this CPU needs another grace period, it will take
969 * care of this while initializing the next grace period.
970 * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL
971 * because the callbacks have not yet been advanced: Those
972 * callbacks are waiting on the grace period that just now
973 * completed.
974 */
975 if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {
976 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
977
978 /*
979 * Propagate new ->completed value to rcu_node structures
980 * so that other CPUs don't have to wait until the start
981 * of the next grace period to process their callbacks.
982 */
983 rcu_for_each_node_breadth_first(rsp, rnp) {
984 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
985 rnp->completed = rsp->gpnum;
986 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
987 }
988 rnp = rcu_get_root(rsp);
989 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
990 }
991
992 rsp->completed = rsp->gpnum; /* Declare the grace period complete. */
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -0700993 trace_rcu_grace_period(rsp->name, rsp->completed, "end");
Paul E. McKenney83f5b012009-10-28 08:14:49 -0700994 rsp->signaled = RCU_GP_IDLE;
Paul E. McKenneyf41d9112009-08-22 13:56:52 -0700995 rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
996}
997
998/*
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -0800999 * Similar to rcu_report_qs_rdp(), for which it is a helper function.
1000 * Allows quiescent states for a group of CPUs to be reported at one go
1001 * to the specified rcu_node structure, though all the CPUs in the group
1002 * must be represented by the same rcu_node structure (which need not be
1003 * a leaf rcu_node structure, though it often will be). That structure's
1004 * lock must be held upon entry, and it is released before return.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001005 */
1006static void
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001007rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
1008 struct rcu_node *rnp, unsigned long flags)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001009 __releases(rnp->lock)
1010{
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001011 struct rcu_node *rnp_c;
1012
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001013 /* Walk up the rcu_node hierarchy. */
1014 for (;;) {
1015 if (!(rnp->qsmask & mask)) {
1016
1017 /* Our bit has already been cleared, so done. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001018 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001019 return;
1020 }
1021 rnp->qsmask &= ~mask;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001022 trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
1023 mask, rnp->qsmask, rnp->level,
1024 rnp->grplo, rnp->grphi,
1025 !!rnp->gp_tasks);
Paul E. McKenney27f4d282011-02-07 12:47:15 -08001026 if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001027
1028 /* Other bits still set at this level, so done. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001029 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001030 return;
1031 }
1032 mask = rnp->grpmask;
1033 if (rnp->parent == NULL) {
1034
1035 /* No more levels. Exit loop holding root lock. */
1036
1037 break;
1038 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001039 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001040 rnp_c = rnp;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001041 rnp = rnp->parent;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001042 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001043 WARN_ON_ONCE(rnp_c->qsmask);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001044 }
1045
1046 /*
1047 * Get here if we are the last CPU to pass through a quiescent
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001048 * state for this grace period. Invoke rcu_report_qs_rsp()
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001049 * to clean up and start the next grace period if one is needed.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001050 */
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001051 rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001052}
1053
1054/*
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001055 * Record a quiescent state for the specified CPU to that CPU's rcu_data
1056 * structure. This must be either called from the specified CPU, or
1057 * called when the specified CPU is known to be offline (and when it is
1058 * also known that no other CPU is concurrently trying to help the offline
1059 * CPU). The lastcomp argument is used to make sure we are still in the
1060 * grace period of interest. We don't want to end the current grace period
1061 * based on quiescent states detected in an earlier grace period!
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001062 */
1063static void
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001064rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001065{
1066 unsigned long flags;
1067 unsigned long mask;
1068 struct rcu_node *rnp;
1069
1070 rnp = rdp->mynode;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001071 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001072 if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001073
1074 /*
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001075 * The grace period in which this quiescent state was
1076 * recorded has ended, so don't report it upwards.
1077 * We will instead need a new quiescent state that lies
1078 * within the current grace period.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001079 */
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001080 rdp->passed_quiesce = 0; /* need qs for new gp. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001081 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001082 return;
1083 }
1084 mask = rdp->grpmask;
1085 if ((rnp->qsmask & mask) == 0) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001086 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001087 } else {
1088 rdp->qs_pending = 0;
1089
1090 /*
1091 * This GP can't end until cpu checks in, so all of our
1092 * callbacks can be processed during the next GP.
1093 */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001094 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
1095
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001096 rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001097 }
1098}
1099
1100/*
1101 * Check to see if there is a new grace period of which this CPU
1102 * is not yet aware, and if so, set up local rcu_data state for it.
1103 * Otherwise, see if this CPU has just passed through its first
1104 * quiescent state for this grace period, and record that fact if so.
1105 */
1106static void
1107rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
1108{
1109 /* If there is now a new grace period, record and return. */
1110 if (check_for_new_grace_period(rsp, rdp))
1111 return;
1112
1113 /*
1114 * Does this CPU still need to do its part for current grace period?
1115 * If no, return and let the other CPUs do their part as well.
1116 */
1117 if (!rdp->qs_pending)
1118 return;
1119
1120 /*
1121 * Was there a quiescent state since the beginning of the grace
1122 * period? If no, then exit and wait for the next call.
1123 */
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001124 if (!rdp->passed_quiesce)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001125 return;
1126
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001127 /*
1128 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
1129 * judge of that).
1130 */
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001131 rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001132}
1133
1134#ifdef CONFIG_HOTPLUG_CPU
1135
1136/*
Lai Jiangshan29494be2010-10-20 14:13:06 +08001137 * Move a dying CPU's RCU callbacks to online CPU's callback list.
1138 * Synchronization is not required because this function executes
1139 * in stop_machine() context.
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001140 */
Lai Jiangshan29494be2010-10-20 14:13:06 +08001141static void rcu_send_cbs_to_online(struct rcu_state *rsp)
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001142{
1143 int i;
Lai Jiangshan29494be2010-10-20 14:13:06 +08001144 /* current DYING CPU is cleared in the cpu_online_mask */
1145 int receive_cpu = cpumask_any(cpu_online_mask);
Lai Jiangshan394f99a2010-06-28 16:25:04 +08001146 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
Lai Jiangshan29494be2010-10-20 14:13:06 +08001147 struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu);
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001148
1149 if (rdp->nxtlist == NULL)
1150 return; /* irqs disabled, so comparison is stable. */
Lai Jiangshan29494be2010-10-20 14:13:06 +08001151
1152 *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
1153 receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
1154 receive_rdp->qlen += rdp->qlen;
1155 receive_rdp->n_cbs_adopted += rdp->qlen;
1156 rdp->n_cbs_orphaned += rdp->qlen;
1157
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001158 rdp->nxtlist = NULL;
1159 for (i = 0; i < RCU_NEXT_SIZE; i++)
1160 rdp->nxttail[i] = &rdp->nxtlist;
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001161 rdp->qlen = 0;
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001162}
1163
1164/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001165 * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
1166 * and move all callbacks from the outgoing CPU to the current one.
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001167 * There can only be one CPU hotplug operation at a time, so no other
1168 * CPU can be attempting to update rcu_cpu_kthread_task.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001169 */
1170static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
1171{
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001172 unsigned long flags;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001173 unsigned long mask;
Paul E. McKenneyd9a3da02009-12-02 12:10:15 -08001174 int need_report = 0;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08001175 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001176 struct rcu_node *rnp;
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001177
Paul E. McKenneyf8b7fc62011-06-16 08:26:32 -07001178 rcu_stop_cpu_kthread(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001179
1180 /* Exclude any attempts to start a new grace period. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001181 raw_spin_lock_irqsave(&rsp->onofflock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001182
1183 /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
Paul E. McKenney28ecd582009-09-18 09:50:17 -07001184 rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001185 mask = rdp->grpmask; /* rnp->grplo is constant. */
1186 do {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001187 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001188 rnp->qsmaskinit &= ~mask;
1189 if (rnp->qsmaskinit != 0) {
Paul E. McKenneyb668c9c2009-11-22 08:53:48 -08001190 if (rnp != rdp->mynode)
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001191 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001192 else
1193 trace_rcu_grace_period(rsp->name,
1194 rnp->gpnum + 1 -
1195 !!(rnp->qsmask & mask),
1196 "cpuofl");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001197 break;
1198 }
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001199 if (rnp == rdp->mynode) {
1200 trace_rcu_grace_period(rsp->name,
1201 rnp->gpnum + 1 -
1202 !!(rnp->qsmask & mask),
1203 "cpuofl");
Paul E. McKenneyd9a3da02009-12-02 12:10:15 -08001204 need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001205 } else
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001206 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001207 mask = rnp->grpmask;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001208 rnp = rnp->parent;
1209 } while (rnp != NULL);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001210
Paul E. McKenneyb668c9c2009-11-22 08:53:48 -08001211 /*
1212 * We still hold the leaf rcu_node structure lock here, and
1213 * irqs are still disabled. The reason for this subterfuge is
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001214 * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
1215 * held leads to deadlock.
Paul E. McKenneyb668c9c2009-11-22 08:53:48 -08001216 */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001217 raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
Paul E. McKenneyb668c9c2009-11-22 08:53:48 -08001218 rnp = rdp->mynode;
Paul E. McKenneyd9a3da02009-12-02 12:10:15 -08001219 if (need_report & RCU_OFL_TASKS_NORM_GP)
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001220 rcu_report_unblock_qs_rnp(rnp, flags);
Paul E. McKenneyb668c9c2009-11-22 08:53:48 -08001221 else
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001222 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenneyd9a3da02009-12-02 12:10:15 -08001223 if (need_report & RCU_OFL_TASKS_EXP_GP)
1224 rcu_report_exp_rnp(rsp, rnp);
Paul E. McKenney1217ed12011-05-04 21:43:49 -07001225 rcu_node_kthread_setaffinity(rnp, -1);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001226}
1227
1228/*
1229 * Remove the specified CPU from the RCU hierarchy and move any pending
1230 * callbacks that it might have to the current CPU. This code assumes
1231 * that at least one CPU in the system will remain running at all times.
1232 * Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
1233 */
1234static void rcu_offline_cpu(int cpu)
1235{
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001236 __rcu_offline_cpu(cpu, &rcu_sched_state);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001237 __rcu_offline_cpu(cpu, &rcu_bh_state);
Paul E. McKenney33f76142009-08-24 09:42:01 -07001238 rcu_preempt_offline_cpu(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001239}
1240
1241#else /* #ifdef CONFIG_HOTPLUG_CPU */
1242
Lai Jiangshan29494be2010-10-20 14:13:06 +08001243static void rcu_send_cbs_to_online(struct rcu_state *rsp)
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001244{
1245}
1246
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001247static void rcu_offline_cpu(int cpu)
1248{
1249}
1250
1251#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
1252
1253/*
1254 * Invoke any RCU callbacks that have made it to the end of their grace
1255 * period. Thottle as specified by rdp->blimit.
1256 */
Paul E. McKenney37c72e52009-10-14 10:15:55 -07001257static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001258{
1259 unsigned long flags;
1260 struct rcu_head *next, *list, **tail;
Paul E. McKenney29c00b42011-06-17 15:53:19 -07001261 int bl, count;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001262
1263 /* If no callbacks are ready, just return.*/
Paul E. McKenney29c00b42011-06-17 15:53:19 -07001264 if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
Paul E. McKenney72fe7012011-06-21 01:14:54 -07001265 trace_rcu_batch_start(rsp->name, 0, 0);
1266 trace_rcu_batch_end(rsp->name, 0);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001267 return;
Paul E. McKenney29c00b42011-06-17 15:53:19 -07001268 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001269
1270 /*
1271 * Extract the list of ready callbacks, disabling to prevent
1272 * races with call_rcu() from interrupt handlers.
1273 */
1274 local_irq_save(flags);
Paul E. McKenney29c00b42011-06-17 15:53:19 -07001275 bl = rdp->blimit;
Paul E. McKenney72fe7012011-06-21 01:14:54 -07001276 trace_rcu_batch_start(rsp->name, rdp->qlen, bl);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001277 list = rdp->nxtlist;
1278 rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
1279 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
1280 tail = rdp->nxttail[RCU_DONE_TAIL];
1281 for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
1282 if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
1283 rdp->nxttail[count] = &rdp->nxtlist;
1284 local_irq_restore(flags);
1285
1286 /* Invoke callbacks. */
1287 count = 0;
1288 while (list) {
1289 next = list->next;
1290 prefetch(next);
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -04001291 debug_rcu_head_unqueue(list);
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001292 __rcu_reclaim(rsp->name, list);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001293 list = next;
Paul E. McKenney29c00b42011-06-17 15:53:19 -07001294 if (++count >= bl)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001295 break;
1296 }
1297
1298 local_irq_save(flags);
Paul E. McKenney72fe7012011-06-21 01:14:54 -07001299 trace_rcu_batch_end(rsp->name, count);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001300
1301 /* Update count, and requeue any remaining callbacks. */
1302 rdp->qlen -= count;
Paul E. McKenney269dcc12010-09-07 14:23:09 -07001303 rdp->n_cbs_invoked += count;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001304 if (list != NULL) {
1305 *tail = rdp->nxtlist;
1306 rdp->nxtlist = list;
1307 for (count = 0; count < RCU_NEXT_SIZE; count++)
1308 if (&rdp->nxtlist == rdp->nxttail[count])
1309 rdp->nxttail[count] = tail;
1310 else
1311 break;
1312 }
1313
1314 /* Reinstate batch limit if we have worked down the excess. */
1315 if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
1316 rdp->blimit = blimit;
1317
Paul E. McKenney37c72e52009-10-14 10:15:55 -07001318 /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
1319 if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
1320 rdp->qlen_last_fqs_check = 0;
1321 rdp->n_force_qs_snap = rsp->n_force_qs;
1322 } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
1323 rdp->qlen_last_fqs_check = rdp->qlen;
1324
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001325 local_irq_restore(flags);
1326
Paul E. McKenneye0f23062011-06-21 01:29:39 -07001327 /* Re-invoke RCU core processing if there are callbacks remaining. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001328 if (cpu_has_callbacks_ready_to_invoke(rdp))
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001329 invoke_rcu_core();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001330}
1331
1332/*
1333 * Check to see if this CPU is in a non-context-switch quiescent state
1334 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
Paul E. McKenneye0f23062011-06-21 01:29:39 -07001335 * Also schedule RCU core processing.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001336 *
1337 * This function must be called with hardirqs disabled. It is normally
1338 * invoked from the scheduling-clock interrupt. If rcu_pending returns
1339 * false, there is no point in invoking rcu_check_callbacks().
1340 */
1341void rcu_check_callbacks(int cpu, int user)
1342{
Paul E. McKenney300df912011-06-18 22:26:31 -07001343 trace_rcu_utilization("Start scheduler-tick");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001344 if (user ||
Paul E. McKenneya6826042009-02-25 18:03:42 -08001345 (idle_cpu(cpu) && rcu_scheduler_active &&
1346 !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001347
1348 /*
1349 * Get here if this CPU took its interrupt from user
1350 * mode or from the idle loop, and if this is not a
1351 * nested interrupt. In this case, the CPU is in
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001352 * a quiescent state, so note it.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001353 *
1354 * No memory barrier is required here because both
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001355 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
1356 * variables that other CPUs neither access nor modify,
1357 * at least not while the corresponding CPU is online.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001358 */
1359
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001360 rcu_sched_qs(cpu);
1361 rcu_bh_qs(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001362
1363 } else if (!in_softirq()) {
1364
1365 /*
1366 * Get here if this CPU did not take its interrupt from
1367 * softirq, in other words, if it is not interrupting
1368 * a rcu_bh read-side critical section. This is an _bh
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001369 * critical section, so note it.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001370 */
1371
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001372 rcu_bh_qs(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001373 }
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001374 rcu_preempt_check_callbacks(cpu);
Paul E. McKenneyd21670a2010-04-14 17:39:26 -07001375 if (rcu_pending(cpu))
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001376 invoke_rcu_core();
Paul E. McKenney300df912011-06-18 22:26:31 -07001377 trace_rcu_utilization("End scheduler-tick");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001378}
1379
1380#ifdef CONFIG_SMP
1381
1382/*
1383 * Scan the leaf rcu_node structures, processing dyntick state for any that
1384 * have not yet encountered a quiescent state, using the function specified.
Paul E. McKenney27f4d282011-02-07 12:47:15 -08001385 * Also initiate boosting for any threads blocked on the root rcu_node.
1386 *
Paul E. McKenneyee47eb92010-01-04 15:09:07 -08001387 * The caller must have suppressed start of new grace periods.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001388 */
Paul E. McKenney45f014c52e2010-01-04 15:09:08 -08001389static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001390{
1391 unsigned long bit;
1392 int cpu;
1393 unsigned long flags;
1394 unsigned long mask;
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07001395 struct rcu_node *rnp;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001396
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07001397 rcu_for_each_leaf_node(rsp, rnp) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001398 mask = 0;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001399 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenneyee47eb92010-01-04 15:09:07 -08001400 if (!rcu_gp_in_progress(rsp)) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001401 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney0f10dc822010-01-04 15:09:06 -08001402 return;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001403 }
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07001404 if (rnp->qsmask == 0) {
Paul E. McKenney1217ed12011-05-04 21:43:49 -07001405 rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001406 continue;
1407 }
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07001408 cpu = rnp->grplo;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001409 bit = 1;
Paul E. McKenneya0b6c9a2009-09-28 07:46:33 -07001410 for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
Lai Jiangshan394f99a2010-06-28 16:25:04 +08001411 if ((rnp->qsmask & bit) != 0 &&
1412 f(per_cpu_ptr(rsp->rda, cpu)))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001413 mask |= bit;
1414 }
Paul E. McKenney45f014c52e2010-01-04 15:09:08 -08001415 if (mask != 0) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001416
Paul E. McKenneyd3f6bad2009-12-02 12:10:13 -08001417 /* rcu_report_qs_rnp() releases rnp->lock. */
1418 rcu_report_qs_rnp(mask, rsp, rnp, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001419 continue;
1420 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001421 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001422 }
Paul E. McKenney27f4d282011-02-07 12:47:15 -08001423 rnp = rcu_get_root(rsp);
Paul E. McKenney1217ed12011-05-04 21:43:49 -07001424 if (rnp->qsmask == 0) {
1425 raw_spin_lock_irqsave(&rnp->lock, flags);
1426 rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
1427 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001428}
1429
1430/*
1431 * Force quiescent states on reluctant CPUs, and also detect which
1432 * CPUs are in dyntick-idle mode.
1433 */
1434static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1435{
1436 unsigned long flags;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001437 struct rcu_node *rnp = rcu_get_root(rsp);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001438
Paul E. McKenney300df912011-06-18 22:26:31 -07001439 trace_rcu_utilization("Start fqs");
1440 if (!rcu_gp_in_progress(rsp)) {
1441 trace_rcu_utilization("End fqs");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001442 return; /* No grace period in progress, nothing to force. */
Paul E. McKenney300df912011-06-18 22:26:31 -07001443 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001444 if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001445 rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
Paul E. McKenney300df912011-06-18 22:26:31 -07001446 trace_rcu_utilization("End fqs");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001447 return; /* Someone else is already on the job. */
1448 }
Paul E. McKenney20133cf2010-02-22 17:05:01 -08001449 if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
Paul E. McKenneyf96e9232010-01-04 15:09:00 -08001450 goto unlock_fqs_ret; /* no emergency and done recently. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001451 rsp->n_force_qs++;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001452 raw_spin_lock(&rnp->lock); /* irqs already disabled */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001453 rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
Paul E. McKenney560d4bc2009-11-13 19:51:38 -08001454 if(!rcu_gp_in_progress(rsp)) {
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001455 rsp->n_force_qs_ngp++;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001456 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
Paul E. McKenneyf96e9232010-01-04 15:09:00 -08001457 goto unlock_fqs_ret; /* no GP in progress, time updated. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001458 }
Paul E. McKenney07079d52010-01-04 15:09:02 -08001459 rsp->fqs_active = 1;
Paul E. McKenneyf3a8b5c2010-01-04 15:09:03 -08001460 switch (rsp->signaled) {
Paul E. McKenney83f5b012009-10-28 08:14:49 -07001461 case RCU_GP_IDLE:
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001462 case RCU_GP_INIT:
1463
Paul E. McKenney83f5b012009-10-28 08:14:49 -07001464 break; /* grace period idle or initializing, ignore. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001465
1466 case RCU_SAVE_DYNTICK:
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001467 if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
1468 break; /* So gcc recognizes the dead code. */
1469
Lai Jiangshanf2614142010-03-28 11:15:20 +08001470 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
1471
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001472 /* Record dyntick-idle state. */
Paul E. McKenney45f014c52e2010-01-04 15:09:08 -08001473 force_qs_rnp(rsp, dyntick_save_progress_counter);
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001474 raw_spin_lock(&rnp->lock); /* irqs already disabled */
Paul E. McKenneyee47eb92010-01-04 15:09:07 -08001475 if (rcu_gp_in_progress(rsp))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001476 rsp->signaled = RCU_FORCE_QS;
Paul E. McKenneyee47eb92010-01-04 15:09:07 -08001477 break;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001478
1479 case RCU_FORCE_QS:
1480
1481 /* Check dyntick-idle state, send IPI to laggarts. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001482 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
Paul E. McKenney45f014c52e2010-01-04 15:09:08 -08001483 force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001484
1485 /* Leave state in case more forcing is required. */
1486
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001487 raw_spin_lock(&rnp->lock); /* irqs already disabled */
Paul E. McKenneyf96e9232010-01-04 15:09:00 -08001488 break;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001489 }
Paul E. McKenney07079d52010-01-04 15:09:02 -08001490 rsp->fqs_active = 0;
Paul E. McKenney46a1e342010-01-04 15:09:09 -08001491 if (rsp->fqs_need_gp) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001492 raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
Paul E. McKenney46a1e342010-01-04 15:09:09 -08001493 rsp->fqs_need_gp = 0;
1494 rcu_start_gp(rsp, flags); /* releases rnp->lock */
Paul E. McKenney300df912011-06-18 22:26:31 -07001495 trace_rcu_utilization("End fqs");
Paul E. McKenney46a1e342010-01-04 15:09:09 -08001496 return;
1497 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001498 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
Paul E. McKenneyf96e9232010-01-04 15:09:00 -08001499unlock_fqs_ret:
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001500 raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
Paul E. McKenney300df912011-06-18 22:26:31 -07001501 trace_rcu_utilization("End fqs");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001502}
1503
1504#else /* #ifdef CONFIG_SMP */
1505
1506static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1507{
1508 set_need_resched();
1509}
1510
1511#endif /* #else #ifdef CONFIG_SMP */
1512
1513/*
Paul E. McKenneye0f23062011-06-21 01:29:39 -07001514 * This does the RCU core processing work for the specified rcu_state
1515 * and rcu_data structures. This may be called only from the CPU to
1516 * whom the rdp belongs.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001517 */
1518static void
1519__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
1520{
1521 unsigned long flags;
1522
Paul E. McKenney2e597552009-08-15 09:53:48 -07001523 WARN_ON_ONCE(rdp->beenonline == 0);
1524
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001525 /*
1526 * If an RCU GP has gone long enough, go check for dyntick
1527 * idle CPUs and, if needed, send resched IPIs.
1528 */
Paul E. McKenney20133cf2010-02-22 17:05:01 -08001529 if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001530 force_quiescent_state(rsp, 1);
1531
1532 /*
1533 * Advance callbacks in response to end of earlier grace
1534 * period that some other CPU ended.
1535 */
1536 rcu_process_gp_end(rsp, rdp);
1537
1538 /* Update RCU state based on any recent quiescent states. */
1539 rcu_check_quiescent_state(rsp, rdp);
1540
1541 /* Does this CPU require a not-yet-started grace period? */
1542 if (cpu_needs_another_gp(rsp, rdp)) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001543 raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001544 rcu_start_gp(rsp, flags); /* releases above lock */
1545 }
1546
1547 /* If there are callbacks ready, invoke them. */
Shaohua Li09223372011-06-14 13:26:25 +08001548 if (cpu_has_callbacks_ready_to_invoke(rdp))
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001549 invoke_rcu_callbacks(rsp, rdp);
Shaohua Li09223372011-06-14 13:26:25 +08001550}
1551
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001552/*
Paul E. McKenneye0f23062011-06-21 01:29:39 -07001553 * Do RCU core processing for the current CPU.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001554 */
Shaohua Li09223372011-06-14 13:26:25 +08001555static void rcu_process_callbacks(struct softirq_action *unused)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001556{
Paul E. McKenney300df912011-06-18 22:26:31 -07001557 trace_rcu_utilization("Start RCU core");
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001558 __rcu_process_callbacks(&rcu_sched_state,
1559 &__get_cpu_var(rcu_sched_data));
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001560 __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001561 rcu_preempt_process_callbacks();
Paul E. McKenney300df912011-06-18 22:26:31 -07001562 trace_rcu_utilization("End RCU core");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001563}
1564
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001565/*
Paul E. McKenneye0f23062011-06-21 01:29:39 -07001566 * Schedule RCU callback invocation. If the specified type of RCU
1567 * does not support RCU priority boosting, just do a direct call,
1568 * otherwise wake up the per-CPU kernel kthread. Note that because we
1569 * are running on the current CPU with interrupts disabled, the
1570 * rcu_cpu_kthread_task cannot disappear out from under us.
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001571 */
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001572static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001573{
Paul E. McKenneyb0d30412011-07-10 15:57:35 -07001574 if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
1575 return;
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001576 if (likely(!rsp->boost)) {
1577 rcu_do_batch(rsp, rdp);
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001578 return;
1579 }
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001580 invoke_rcu_callbacks_kthread();
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001581}
1582
Paul E. McKenneya46e0892011-06-15 15:47:09 -07001583static void invoke_rcu_core(void)
Shaohua Li09223372011-06-14 13:26:25 +08001584{
1585 raise_softirq(RCU_SOFTIRQ);
1586}
1587
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001588static void
1589__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
1590 struct rcu_state *rsp)
1591{
1592 unsigned long flags;
1593 struct rcu_data *rdp;
1594
Mathieu Desnoyers551d55a2010-04-17 08:48:42 -04001595 debug_rcu_head_queue(head);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001596 head->func = func;
1597 head->next = NULL;
1598
1599 smp_mb(); /* Ensure RCU update seen before callback registry. */
1600
1601 /*
1602 * Opportunistically note grace-period endings and beginnings.
1603 * Note that we might see a beginning right after we see an
1604 * end, but never vice versa, since this CPU has to pass through
1605 * a quiescent state betweentimes.
1606 */
1607 local_irq_save(flags);
Lai Jiangshan394f99a2010-06-28 16:25:04 +08001608 rdp = this_cpu_ptr(rsp->rda);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001609
1610 /* Add the callback to our list. */
1611 *rdp->nxttail[RCU_NEXT_TAIL] = head;
1612 rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
Paul E. McKenney2655d572011-04-07 22:47:23 -07001613 rdp->qlen++;
1614
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001615 if (__is_kfree_rcu_offset((unsigned long)func))
1616 trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
1617 rdp->qlen);
1618 else
1619 trace_rcu_callback(rsp->name, head, rdp->qlen);
1620
Paul E. McKenney2655d572011-04-07 22:47:23 -07001621 /* If interrupts were disabled, don't dive into RCU core. */
1622 if (irqs_disabled_flags(flags)) {
1623 local_irq_restore(flags);
1624 return;
1625 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001626
Paul E. McKenney37c72e52009-10-14 10:15:55 -07001627 /*
1628 * Force the grace period if too many callbacks or too long waiting.
1629 * Enforce hysteresis, and don't invoke force_quiescent_state()
1630 * if some other CPU has recently done so. Also, don't bother
1631 * invoking force_quiescent_state() if the newly enqueued callback
1632 * is the only one waiting for a grace period to complete.
1633 */
Paul E. McKenney2655d572011-04-07 22:47:23 -07001634 if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
Paul E. McKenneyb52573d2010-12-14 17:36:02 -08001635
1636 /* Are we ignoring a completed grace period? */
1637 rcu_process_gp_end(rsp, rdp);
1638 check_for_new_grace_period(rsp, rdp);
1639
1640 /* Start a new grace period if one not already started. */
1641 if (!rcu_gp_in_progress(rsp)) {
1642 unsigned long nestflag;
1643 struct rcu_node *rnp_root = rcu_get_root(rsp);
1644
1645 raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
1646 rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */
1647 } else {
1648 /* Give the grace period a kick. */
1649 rdp->blimit = LONG_MAX;
1650 if (rsp->n_force_qs == rdp->n_force_qs_snap &&
1651 *rdp->nxttail[RCU_DONE_TAIL] != head)
1652 force_quiescent_state(rsp, 0);
1653 rdp->n_force_qs_snap = rsp->n_force_qs;
1654 rdp->qlen_last_fqs_check = rdp->qlen;
1655 }
Paul E. McKenney20133cf2010-02-22 17:05:01 -08001656 } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001657 force_quiescent_state(rsp, 1);
1658 local_irq_restore(flags);
1659}
1660
1661/*
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001662 * Queue an RCU-sched callback for invocation after a grace period.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001663 */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001664void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001665{
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001666 __call_rcu(head, func, &rcu_sched_state);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001667}
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001668EXPORT_SYMBOL_GPL(call_rcu_sched);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001669
1670/*
1671 * Queue an RCU for invocation after a quicker grace period.
1672 */
1673void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
1674{
1675 __call_rcu(head, func, &rcu_bh_state);
1676}
1677EXPORT_SYMBOL_GPL(call_rcu_bh);
1678
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08001679/**
1680 * synchronize_sched - wait until an rcu-sched grace period has elapsed.
1681 *
1682 * Control will return to the caller some time after a full rcu-sched
1683 * grace period has elapsed, in other words after all currently executing
1684 * rcu-sched read-side critical sections have completed. These read-side
1685 * critical sections are delimited by rcu_read_lock_sched() and
1686 * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
1687 * local_irq_disable(), and so on may be used in place of
1688 * rcu_read_lock_sched().
1689 *
1690 * This means that all preempt_disable code sequences, including NMI and
1691 * hardware-interrupt handlers, in progress on entry will have completed
1692 * before this primitive returns. However, this does not guarantee that
1693 * softirq handlers will have completed, since in some kernels, these
1694 * handlers can run in process context, and can block.
1695 *
1696 * This primitive provides the guarantees made by the (now removed)
1697 * synchronize_kernel() API. In contrast, synchronize_rcu() only
1698 * guarantees that rcu_read_lock() sections will have completed.
1699 * In "classic RCU", these two guarantees happen to be one and
1700 * the same, but can differ in realtime RCU implementations.
1701 */
1702void synchronize_sched(void)
1703{
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08001704 if (rcu_blocking_is_gp())
1705 return;
Paul E. McKenney2c428182011-05-26 22:14:36 -07001706 wait_rcu_gp(call_rcu_sched);
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08001707}
1708EXPORT_SYMBOL_GPL(synchronize_sched);
1709
1710/**
1711 * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
1712 *
1713 * Control will return to the caller some time after a full rcu_bh grace
1714 * period has elapsed, in other words after all currently executing rcu_bh
1715 * read-side critical sections have completed. RCU read-side critical
1716 * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
1717 * and may be nested.
1718 */
1719void synchronize_rcu_bh(void)
1720{
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08001721 if (rcu_blocking_is_gp())
1722 return;
Paul E. McKenney2c428182011-05-26 22:14:36 -07001723 wait_rcu_gp(call_rcu_bh);
Paul E. McKenney6ebb2372009-11-22 08:53:50 -08001724}
1725EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
1726
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001727/*
1728 * Check to see if there is any immediate RCU-related work to be done
1729 * by the current CPU, for the specified type of RCU, returning 1 if so.
1730 * The checks are in order of increasing expense: checks that can be
1731 * carried out against CPU-local state are performed first. However,
1732 * we must check for CPU stalls first, else we might not get a chance.
1733 */
1734static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
1735{
Paul E. McKenney2f51f982009-11-13 19:51:39 -08001736 struct rcu_node *rnp = rdp->mynode;
1737
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001738 rdp->n_rcu_pending++;
1739
1740 /* Check for CPU stalls, if enabled. */
1741 check_cpu_stall(rsp, rdp);
1742
1743 /* Is the RCU core waiting for a quiescent state from this CPU? */
Paul E. McKenney5c51dd72011-08-04 06:59:03 -07001744 if (rcu_scheduler_fully_active &&
1745 rdp->qs_pending && !rdp->passed_quiesce) {
Paul E. McKenneyd25eb942010-03-18 21:36:51 -07001746
1747 /*
1748 * If force_quiescent_state() coming soon and this CPU
1749 * needs a quiescent state, and this is either RCU-sched
1750 * or RCU-bh, force a local reschedule.
1751 */
Paul E. McKenneyd21670a2010-04-14 17:39:26 -07001752 rdp->n_rp_qs_pending++;
Paul E. McKenney6cc68792011-03-02 13:15:15 -08001753 if (!rdp->preemptible &&
Paul E. McKenneyd25eb942010-03-18 21:36:51 -07001754 ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
1755 jiffies))
1756 set_need_resched();
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001757 } else if (rdp->qs_pending && rdp->passed_quiesce) {
Paul E. McKenneyd21670a2010-04-14 17:39:26 -07001758 rdp->n_rp_report_qs++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001759 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001760 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001761
1762 /* Does this CPU have callbacks ready to invoke? */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001763 if (cpu_has_callbacks_ready_to_invoke(rdp)) {
1764 rdp->n_rp_cb_ready++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001765 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001766 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001767
1768 /* Has RCU gone idle with this CPU needing another grace period? */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001769 if (cpu_needs_another_gp(rsp, rdp)) {
1770 rdp->n_rp_cpu_needs_gp++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001771 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001772 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001773
1774 /* Has another RCU grace period completed? */
Paul E. McKenney2f51f982009-11-13 19:51:39 -08001775 if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001776 rdp->n_rp_gp_completed++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001777 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001778 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001779
1780 /* Has a new RCU grace period started? */
Paul E. McKenney2f51f982009-11-13 19:51:39 -08001781 if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001782 rdp->n_rp_gp_started++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001783 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001784 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001785
1786 /* Has an RCU GP gone long enough to send resched IPIs &c? */
Paul E. McKenneyfc2219d2009-09-23 09:50:41 -07001787 if (rcu_gp_in_progress(rsp) &&
Paul E. McKenney20133cf2010-02-22 17:05:01 -08001788 ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001789 rdp->n_rp_need_fqs++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001790 return 1;
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001791 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001792
1793 /* nothing to do */
Paul E. McKenney7ba5c842009-04-13 21:31:17 -07001794 rdp->n_rp_need_nothing++;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001795 return 0;
1796}
1797
1798/*
1799 * Check to see if there is any immediate RCU-related work to be done
1800 * by the current CPU, returning 1 if so. This function is part of the
1801 * RCU implementation; it is -not- an exported member of the RCU API.
1802 */
Paul E. McKenneya1572292009-08-22 13:56:51 -07001803static int rcu_pending(int cpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001804{
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001805 return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001806 __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
1807 rcu_preempt_pending(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001808}
1809
1810/*
1811 * Check to see if any future RCU-related work will need to be done
1812 * by the current CPU, even if none need be done immediately, returning
Paul E. McKenney8bd93a22010-02-22 17:04:59 -08001813 * 1 if so.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001814 */
Paul E. McKenney8bd93a22010-02-22 17:04:59 -08001815static int rcu_needs_cpu_quick_check(int cpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001816{
1817 /* RCU callbacks either ready or pending? */
Paul E. McKenneyd6714c22009-08-22 13:56:46 -07001818 return per_cpu(rcu_sched_data, cpu).nxtlist ||
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001819 per_cpu(rcu_bh_data, cpu).nxtlist ||
1820 rcu_preempt_needs_cpu(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001821}
1822
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001823static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
1824static atomic_t rcu_barrier_cpu_count;
1825static DEFINE_MUTEX(rcu_barrier_mutex);
1826static struct completion rcu_barrier_completion;
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001827
1828static void rcu_barrier_callback(struct rcu_head *notused)
1829{
1830 if (atomic_dec_and_test(&rcu_barrier_cpu_count))
1831 complete(&rcu_barrier_completion);
1832}
1833
1834/*
1835 * Called with preemption disabled, and from cross-cpu IRQ context.
1836 */
1837static void rcu_barrier_func(void *type)
1838{
1839 int cpu = smp_processor_id();
1840 struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
1841 void (*call_rcu_func)(struct rcu_head *head,
1842 void (*func)(struct rcu_head *head));
1843
1844 atomic_inc(&rcu_barrier_cpu_count);
1845 call_rcu_func = type;
1846 call_rcu_func(head, rcu_barrier_callback);
1847}
1848
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001849/*
1850 * Orchestrate the specified type of RCU barrier, waiting for all
1851 * RCU callbacks of the specified type to complete.
1852 */
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001853static void _rcu_barrier(struct rcu_state *rsp,
1854 void (*call_rcu_func)(struct rcu_head *head,
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001855 void (*func)(struct rcu_head *head)))
1856{
1857 BUG_ON(in_interrupt());
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001858 /* Take mutex to serialize concurrent rcu_barrier() requests. */
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001859 mutex_lock(&rcu_barrier_mutex);
1860 init_completion(&rcu_barrier_completion);
1861 /*
1862 * Initialize rcu_barrier_cpu_count to 1, then invoke
1863 * rcu_barrier_func() on each CPU, so that each CPU also has
1864 * incremented rcu_barrier_cpu_count. Only then is it safe to
1865 * decrement rcu_barrier_cpu_count -- otherwise the first CPU
1866 * might complete its grace period before all of the other CPUs
1867 * did their increment, causing this function to return too
Paul E. McKenney2d999e02010-10-20 12:06:18 -07001868 * early. Note that on_each_cpu() disables irqs, which prevents
1869 * any CPUs from coming online or going offline until each online
1870 * CPU has queued its RCU-barrier callback.
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001871 */
1872 atomic_set(&rcu_barrier_cpu_count, 1);
1873 on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
1874 if (atomic_dec_and_test(&rcu_barrier_cpu_count))
1875 complete(&rcu_barrier_completion);
1876 wait_for_completion(&rcu_barrier_completion);
1877 mutex_unlock(&rcu_barrier_mutex);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001878}
1879
1880/**
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001881 * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
1882 */
1883void rcu_barrier_bh(void)
1884{
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001885 _rcu_barrier(&rcu_bh_state, call_rcu_bh);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001886}
1887EXPORT_SYMBOL_GPL(rcu_barrier_bh);
1888
1889/**
1890 * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
1891 */
1892void rcu_barrier_sched(void)
1893{
Paul E. McKenneye74f4c42009-10-06 21:48:17 -07001894 _rcu_barrier(&rcu_sched_state, call_rcu_sched);
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07001895}
1896EXPORT_SYMBOL_GPL(rcu_barrier_sched);
1897
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001898/*
Paul E. McKenney27569622009-08-15 09:53:46 -07001899 * Do boot-time initialization of a CPU's per-CPU RCU data.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001900 */
Paul E. McKenney27569622009-08-15 09:53:46 -07001901static void __init
1902rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001903{
1904 unsigned long flags;
1905 int i;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08001906 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney27569622009-08-15 09:53:46 -07001907 struct rcu_node *rnp = rcu_get_root(rsp);
1908
1909 /* Set up local state, ensuring consistent view of global state. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001910 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney27569622009-08-15 09:53:46 -07001911 rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
1912 rdp->nxtlist = NULL;
1913 for (i = 0; i < RCU_NEXT_SIZE; i++)
1914 rdp->nxttail[i] = &rdp->nxtlist;
1915 rdp->qlen = 0;
1916#ifdef CONFIG_NO_HZ
1917 rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
1918#endif /* #ifdef CONFIG_NO_HZ */
1919 rdp->cpu = cpu;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001920 rdp->rsp = rsp;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001921 raw_spin_unlock_irqrestore(&rnp->lock, flags);
Paul E. McKenney27569622009-08-15 09:53:46 -07001922}
1923
1924/*
1925 * Initialize a CPU's per-CPU RCU data. Note that only one online or
1926 * offline event can be happening at a given time. Note also that we
1927 * can accept some slop in the rsp->completed access due to the fact
1928 * that this CPU cannot possibly have any RCU callbacks in flight yet.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001929 */
1930static void __cpuinit
Paul E. McKenney6cc68792011-03-02 13:15:15 -08001931rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001932{
1933 unsigned long flags;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001934 unsigned long mask;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08001935 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001936 struct rcu_node *rnp = rcu_get_root(rsp);
1937
1938 /* Set up local state, ensuring consistent view of global state. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001939 raw_spin_lock_irqsave(&rnp->lock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001940 rdp->beenonline = 1; /* We have now been online. */
Paul E. McKenney6cc68792011-03-02 13:15:15 -08001941 rdp->preemptible = preemptible;
Paul E. McKenney37c72e52009-10-14 10:15:55 -07001942 rdp->qlen_last_fqs_check = 0;
1943 rdp->n_force_qs_snap = rsp->n_force_qs;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001944 rdp->blimit = blimit;
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001945 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001946
1947 /*
1948 * A new grace period might start here. If so, we won't be part
1949 * of it, but that is OK, as we are currently in a quiescent state.
1950 */
1951
1952 /* Exclude any attempts to start a new GP on large systems. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001953 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001954
1955 /* Add CPU to rcu_node bitmasks. */
1956 rnp = rdp->mynode;
1957 mask = rdp->grpmask;
1958 do {
1959 /* Exclude any attempts to start a new GP on small systems. */
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001960 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001961 rnp->qsmaskinit |= mask;
1962 mask = rnp->grpmask;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001963 if (rnp == rdp->mynode) {
Paul E. McKenney06ae115a2011-08-14 15:56:54 -07001964 /*
1965 * If there is a grace period in progress, we will
1966 * set up to wait for it next time we run the
1967 * RCU core code.
1968 */
1969 rdp->gpnum = rnp->completed;
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001970 rdp->completed = rnp->completed;
Paul E. McKenney06ae115a2011-08-14 15:56:54 -07001971 rdp->passed_quiesce = 0;
1972 rdp->qs_pending = 0;
Paul E. McKenneye4cc1f22011-06-27 00:17:43 -07001973 rdp->passed_quiesce_gpnum = rnp->gpnum - 1;
Paul E. McKenneyd4c08f22011-06-25 06:36:56 -07001974 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
Paul E. McKenneyd09b62d2009-11-02 13:52:28 -08001975 }
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001976 raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001977 rnp = rnp->parent;
1978 } while (rnp != NULL && !(rnp->qsmaskinit & mask));
1979
Paul E. McKenney1304afb2010-02-22 17:05:02 -08001980 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001981}
1982
Peter Zijlstrad72bce02011-05-30 13:34:51 +02001983static void __cpuinit rcu_prepare_cpu(int cpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001984{
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001985 rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
1986 rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
1987 rcu_preempt_init_percpu_data(cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001988}
1989
1990/*
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07001991 * Handle CPU online/offline notification events.
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001992 */
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08001993static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
1994 unsigned long action, void *hcpu)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001995{
1996 long cpu = (long)hcpu;
Paul E. McKenney27f4d282011-02-07 12:47:15 -08001997 struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
Paul E. McKenneya26ac242011-01-12 14:10:23 -08001998 struct rcu_node *rnp = rdp->mynode;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001999
Paul E. McKenney300df912011-06-18 22:26:31 -07002000 trace_rcu_utilization("Start CPU hotplug");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002001 switch (action) {
2002 case CPU_UP_PREPARE:
2003 case CPU_UP_PREPARE_FROZEN:
Peter Zijlstrad72bce02011-05-30 13:34:51 +02002004 rcu_prepare_cpu(cpu);
2005 rcu_prepare_kthreads(cpu);
Paul E. McKenneya26ac242011-01-12 14:10:23 -08002006 break;
2007 case CPU_ONLINE:
Paul E. McKenney0f962a52011-04-14 12:13:53 -07002008 case CPU_DOWN_FAILED:
2009 rcu_node_kthread_setaffinity(rnp, -1);
Paul E. McKenneye3995a22011-04-18 15:31:26 -07002010 rcu_cpu_kthread_setrt(cpu, 1);
Paul E. McKenney0f962a52011-04-14 12:13:53 -07002011 break;
2012 case CPU_DOWN_PREPARE:
2013 rcu_node_kthread_setaffinity(rnp, cpu);
Paul E. McKenneye3995a22011-04-18 15:31:26 -07002014 rcu_cpu_kthread_setrt(cpu, 0);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002015 break;
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07002016 case CPU_DYING:
2017 case CPU_DYING_FROZEN:
2018 /*
Paul E. McKenney2d999e02010-10-20 12:06:18 -07002019 * The whole machine is "stopped" except this CPU, so we can
2020 * touch any data without introducing corruption. We send the
2021 * dying CPU's callbacks to an arbitrarily chosen online CPU.
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07002022 */
Lai Jiangshan29494be2010-10-20 14:13:06 +08002023 rcu_send_cbs_to_online(&rcu_bh_state);
2024 rcu_send_cbs_to_online(&rcu_sched_state);
2025 rcu_preempt_send_cbs_to_online();
Paul E. McKenneyd0ec7742009-10-06 21:48:16 -07002026 break;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002027 case CPU_DEAD:
2028 case CPU_DEAD_FROZEN:
2029 case CPU_UP_CANCELED:
2030 case CPU_UP_CANCELED_FROZEN:
2031 rcu_offline_cpu(cpu);
2032 break;
2033 default:
2034 break;
2035 }
Paul E. McKenney300df912011-06-18 22:26:31 -07002036 trace_rcu_utilization("End CPU hotplug");
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002037 return NOTIFY_OK;
2038}
2039
2040/*
Paul E. McKenneybbad9372010-04-02 16:17:17 -07002041 * This function is invoked towards the end of the scheduler's initialization
2042 * process. Before this is called, the idle task might contain
2043 * RCU read-side critical sections (during which time, this idle
2044 * task is booting the system). After this function is called, the
2045 * idle tasks are prohibited from containing RCU read-side critical
2046 * sections. This function also enables RCU lockdep checking.
2047 */
2048void rcu_scheduler_starting(void)
2049{
2050 WARN_ON(num_online_cpus() != 1);
2051 WARN_ON(nr_context_switches() > 0);
2052 rcu_scheduler_active = 1;
2053}
2054
2055/*
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002056 * Compute the per-level fanout, either using the exact fanout specified
2057 * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
2058 */
2059#ifdef CONFIG_RCU_FANOUT_EXACT
2060static void __init rcu_init_levelspread(struct rcu_state *rsp)
2061{
2062 int i;
2063
Paul E. McKenney0209f642010-12-14 16:07:52 -08002064 for (i = NUM_RCU_LVLS - 1; i > 0; i--)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002065 rsp->levelspread[i] = CONFIG_RCU_FANOUT;
Paul E. McKenney0209f642010-12-14 16:07:52 -08002066 rsp->levelspread[0] = RCU_FANOUT_LEAF;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002067}
2068#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
2069static void __init rcu_init_levelspread(struct rcu_state *rsp)
2070{
2071 int ccur;
2072 int cprv;
2073 int i;
2074
2075 cprv = NR_CPUS;
2076 for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
2077 ccur = rsp->levelcnt[i];
2078 rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
2079 cprv = ccur;
2080 }
2081}
2082#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
2083
2084/*
2085 * Helper function for rcu_init() that initializes one rcu_state structure.
2086 */
Lai Jiangshan394f99a2010-06-28 16:25:04 +08002087static void __init rcu_init_one(struct rcu_state *rsp,
2088 struct rcu_data __percpu *rda)
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002089{
Paul E. McKenneyb6407e82010-01-04 16:04:02 -08002090 static char *buf[] = { "rcu_node_level_0",
2091 "rcu_node_level_1",
2092 "rcu_node_level_2",
2093 "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002094 int cpustride = 1;
2095 int i;
2096 int j;
2097 struct rcu_node *rnp;
2098
Paul E. McKenneyb6407e82010-01-04 16:04:02 -08002099 BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
2100
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002101 /* Initialize the level-tracking arrays. */
2102
2103 for (i = 1; i < NUM_RCU_LVLS; i++)
2104 rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
2105 rcu_init_levelspread(rsp);
2106
2107 /* Initialize the elements themselves, starting from the leaves. */
2108
2109 for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
2110 cpustride *= rsp->levelspread[i];
2111 rnp = rsp->level[i];
2112 for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
Paul E. McKenney1304afb2010-02-22 17:05:02 -08002113 raw_spin_lock_init(&rnp->lock);
Paul E. McKenneyb6407e82010-01-04 16:04:02 -08002114 lockdep_set_class_and_name(&rnp->lock,
2115 &rcu_node_class[i], buf[i]);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07002116 rnp->gpnum = 0;
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002117 rnp->qsmask = 0;
2118 rnp->qsmaskinit = 0;
2119 rnp->grplo = j * cpustride;
2120 rnp->grphi = (j + 1) * cpustride - 1;
2121 if (rnp->grphi >= NR_CPUS)
2122 rnp->grphi = NR_CPUS - 1;
2123 if (i == 0) {
2124 rnp->grpnum = 0;
2125 rnp->grpmask = 0;
2126 rnp->parent = NULL;
2127 } else {
2128 rnp->grpnum = j % rsp->levelspread[i - 1];
2129 rnp->grpmask = 1UL << rnp->grpnum;
2130 rnp->parent = rsp->level[i - 1] +
2131 j / rsp->levelspread[i - 1];
2132 }
2133 rnp->level = i;
Paul E. McKenney12f5f522010-11-29 21:56:39 -08002134 INIT_LIST_HEAD(&rnp->blkd_tasks);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002135 }
2136 }
Lai Jiangshan0c340292010-03-28 11:12:30 +08002137
Lai Jiangshan394f99a2010-06-28 16:25:04 +08002138 rsp->rda = rda;
Lai Jiangshan0c340292010-03-28 11:12:30 +08002139 rnp = rsp->level[NUM_RCU_LVLS - 1];
2140 for_each_possible_cpu(i) {
Paul E. McKenney4a90a062010-04-14 16:48:11 -07002141 while (i > rnp->grphi)
Lai Jiangshan0c340292010-03-28 11:12:30 +08002142 rnp++;
Lai Jiangshan394f99a2010-06-28 16:25:04 +08002143 per_cpu_ptr(rsp->rda, i)->mynode = rnp;
Lai Jiangshan0c340292010-03-28 11:12:30 +08002144 rcu_boot_init_percpu_data(i, rsp);
2145 }
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002146}
2147
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08002148void __init rcu_init(void)
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07002149{
Paul E. McKenney017c4262010-01-14 16:10:58 -08002150 int cpu;
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08002151
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07002152 rcu_bootup_announce();
Lai Jiangshan394f99a2010-06-28 16:25:04 +08002153 rcu_init_one(&rcu_sched_state, &rcu_sched_data);
2154 rcu_init_one(&rcu_bh_state, &rcu_bh_data);
Paul E. McKenneyf41d9112009-08-22 13:56:52 -07002155 __rcu_init_preempt();
Shaohua Li09223372011-06-14 13:26:25 +08002156 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
Paul E. McKenney9f680ab2009-11-22 08:53:49 -08002157
2158 /*
2159 * We don't need protection against CPU-hotplug here because
2160 * this is called early in boot, before either interrupts
2161 * or the scheduler are operational.
2162 */
2163 cpu_notifier(rcu_cpu_notify, 0);
Paul E. McKenney017c4262010-01-14 16:10:58 -08002164 for_each_online_cpu(cpu)
2165 rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
Paul E. McKenneyc68de202010-04-15 10:12:40 -07002166 check_cpu_stall_init();
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01002167}
2168
Paul E. McKenney1eba8f82009-09-23 09:50:42 -07002169#include "rcutree_plugin.h"