2 * Read-Copy Update mechanism for mutual exclusion
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.
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.
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.
18 * Copyright IBM Corporation, 2008
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
24 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
25 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
27 * For detailed explanation of Read-Copy Update mechanism see -
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>
38 #include <linux/nmi.h>
39 #include <linux/atomic.h>
40 #include <linux/bitops.h>
41 #include <linux/module.h>
42 #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>
49 #include <linux/kernel_stat.h>
50 #include <linux/wait.h>
51 #include <linux/kthread.h>
52 #include <linux/prefetch.h>
55 #include <trace/events/rcu.h>
59 /* Data structures. */
61 static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
63 #define RCU_STATE_INITIALIZER(structname) { \
64 .level = { &structname##_state.node[0] }, \
66 NUM_RCU_LVL_0, /* root of hierarchy. */ \
70 NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
72 .signaled = RCU_GP_IDLE, \
75 .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \
76 .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.fqslock), \
78 .n_force_qs_ngp = 0, \
79 .name = #structname, \
82 struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched);
83 DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
85 struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh);
86 DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
88 static struct rcu_state *rcu_state;
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.
99 int rcu_scheduler_active __read_mostly;
100 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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.
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
114 static int rcu_scheduler_fully_active __read_mostly;
116 #ifdef CONFIG_RCU_BOOST
119 * Control variables for per-CPU and per-rcu_node kthreads. These
120 * handle all flavors of RCU.
122 static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
123 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
124 DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
125 DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
126 DEFINE_PER_CPU(char, rcu_cpu_has_work);
128 #endif /* #ifdef CONFIG_RCU_BOOST */
130 static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
131 static void invoke_rcu_core(void);
132 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
134 #define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */
137 * Track the rcutorture test sequence number and the update version
138 * number within a given test. The rcutorture_testseq is incremented
139 * on every rcutorture module load and unload, so has an odd value
140 * when a test is running. The rcutorture_vernum is set to zero
141 * when rcutorture starts and is incremented on each rcutorture update.
142 * These variables enable correlating rcutorture output with the
143 * RCU tracing information.
145 unsigned long rcutorture_testseq;
146 unsigned long rcutorture_vernum;
149 * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
150 * permit this function to be invoked without holding the root rcu_node
151 * structure's ->lock, but of course results can be subject to change.
153 static int rcu_gp_in_progress(struct rcu_state *rsp)
155 return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum);
159 * Note a quiescent state. Because we do not need to know
160 * how many quiescent states passed, just if there was at least
161 * one since the start of the grace period, this just sets a flag.
162 * The caller must have disabled preemption.
164 void rcu_sched_qs(int cpu)
166 struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
168 rdp->passed_quiesce_gpnum = rdp->gpnum;
170 if (rdp->passed_quiesce == 0)
171 trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
172 rdp->passed_quiesce = 1;
175 void rcu_bh_qs(int cpu)
177 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
179 rdp->passed_quiesce_gpnum = rdp->gpnum;
181 if (rdp->passed_quiesce == 0)
182 trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
183 rdp->passed_quiesce = 1;
187 * Note a context switch. This is a quiescent state for RCU-sched,
188 * and requires special handling for preemptible RCU.
189 * The caller must have disabled preemption.
191 void rcu_note_context_switch(int cpu)
193 trace_rcu_utilization("Start context switch");
195 rcu_preempt_note_context_switch(cpu);
196 trace_rcu_utilization("End context switch");
198 EXPORT_SYMBOL_GPL(rcu_note_context_switch);
201 DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
202 .dynticks_nesting = 1,
203 .dynticks = ATOMIC_INIT(1),
205 #endif /* #ifdef CONFIG_NO_HZ */
207 static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */
208 static int qhimark = 10000; /* If this many pending, ignore blimit. */
209 static int qlowmark = 100; /* Once only this many pending, use blimit. */
211 module_param(blimit, int, 0);
212 module_param(qhimark, int, 0);
213 module_param(qlowmark, int, 0);
215 int rcu_cpu_stall_suppress __read_mostly;
216 module_param(rcu_cpu_stall_suppress, int, 0644);
218 static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
219 static int rcu_pending(int cpu);
222 * Return the number of RCU-sched batches processed thus far for debug & stats.
224 long rcu_batches_completed_sched(void)
226 return rcu_sched_state.completed;
228 EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
231 * Return the number of RCU BH batches processed thus far for debug & stats.
233 long rcu_batches_completed_bh(void)
235 return rcu_bh_state.completed;
237 EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
240 * Force a quiescent state for RCU BH.
242 void rcu_bh_force_quiescent_state(void)
244 force_quiescent_state(&rcu_bh_state, 0);
246 EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
249 * Record the number of times rcutorture tests have been initiated and
250 * terminated. This information allows the debugfs tracing stats to be
251 * correlated to the rcutorture messages, even when the rcutorture module
252 * is being repeatedly loaded and unloaded. In other words, we cannot
253 * store this state in rcutorture itself.
255 void rcutorture_record_test_transition(void)
257 rcutorture_testseq++;
258 rcutorture_vernum = 0;
260 EXPORT_SYMBOL_GPL(rcutorture_record_test_transition);
263 * Record the number of writer passes through the current rcutorture test.
264 * This is also used to correlate debugfs tracing stats with the rcutorture
267 void rcutorture_record_progress(unsigned long vernum)
271 EXPORT_SYMBOL_GPL(rcutorture_record_progress);
274 * Force a quiescent state for RCU-sched.
276 void rcu_sched_force_quiescent_state(void)
278 force_quiescent_state(&rcu_sched_state, 0);
280 EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
283 * Does the CPU have callbacks ready to be invoked?
286 cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
288 return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL];
292 * Does the current CPU require a yet-as-unscheduled grace period?
295 cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
297 return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
301 * Return the root node of the specified rcu_state structure.
303 static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
305 return &rsp->node[0];
311 * If the specified CPU is offline, tell the caller that it is in
312 * a quiescent state. Otherwise, whack it with a reschedule IPI.
313 * Grace periods can end up waiting on an offline CPU when that
314 * CPU is in the process of coming online -- it will be added to the
315 * rcu_node bitmasks before it actually makes it online. The same thing
316 * can happen while a CPU is in the process of coming online. Because this
317 * race is quite rare, we check for it after detecting that the grace
318 * period has been delayed rather than checking each and every CPU
319 * each and every time we start a new grace period.
321 static int rcu_implicit_offline_qs(struct rcu_data *rdp)
324 * If the CPU is offline, it is in a quiescent state. We can
325 * trust its state not to change because interrupts are disabled.
327 if (cpu_is_offline(rdp->cpu)) {
328 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
333 /* If preemptible RCU, no point in sending reschedule IPI. */
334 if (rdp->preemptible)
337 /* The CPU is online, so send it a reschedule IPI. */
338 if (rdp->cpu != smp_processor_id())
339 smp_send_reschedule(rdp->cpu);
346 #endif /* #ifdef CONFIG_SMP */
351 * rcu_enter_nohz - inform RCU that current CPU is entering nohz
353 * Enter nohz mode, in other words, -leave- the mode in which RCU
354 * read-side critical sections can occur. (Though RCU read-side
355 * critical sections can occur in irq handlers in nohz mode, a possibility
356 * handled by rcu_irq_enter() and rcu_irq_exit()).
358 void rcu_enter_nohz(void)
361 struct rcu_dynticks *rdtp;
363 local_irq_save(flags);
364 rdtp = &__get_cpu_var(rcu_dynticks);
365 if (--rdtp->dynticks_nesting) {
366 local_irq_restore(flags);
369 trace_rcu_dyntick("Start");
370 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
371 smp_mb__before_atomic_inc(); /* See above. */
372 atomic_inc(&rdtp->dynticks);
373 smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
374 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
375 local_irq_restore(flags);
379 * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
381 * Exit nohz mode, in other words, -enter- the mode in which RCU
382 * read-side critical sections normally occur.
384 void rcu_exit_nohz(void)
387 struct rcu_dynticks *rdtp;
389 local_irq_save(flags);
390 rdtp = &__get_cpu_var(rcu_dynticks);
391 if (rdtp->dynticks_nesting++) {
392 local_irq_restore(flags);
395 smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
396 atomic_inc(&rdtp->dynticks);
397 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
398 smp_mb__after_atomic_inc(); /* See above. */
399 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
400 trace_rcu_dyntick("End");
401 local_irq_restore(flags);
405 * rcu_nmi_enter - inform RCU of entry to NMI context
407 * If the CPU was idle with dynamic ticks active, and there is no
408 * irq handler running, this updates rdtp->dynticks_nmi to let the
409 * RCU grace-period handling know that the CPU is active.
411 void rcu_nmi_enter(void)
413 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
415 if (rdtp->dynticks_nmi_nesting == 0 &&
416 (atomic_read(&rdtp->dynticks) & 0x1))
418 rdtp->dynticks_nmi_nesting++;
419 smp_mb__before_atomic_inc(); /* Force delay from prior write. */
420 atomic_inc(&rdtp->dynticks);
421 /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
422 smp_mb__after_atomic_inc(); /* See above. */
423 WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
427 * rcu_nmi_exit - inform RCU of exit from NMI context
429 * If the CPU was idle with dynamic ticks active, and there is no
430 * irq handler running, this updates rdtp->dynticks_nmi to let the
431 * RCU grace-period handling know that the CPU is no longer active.
433 void rcu_nmi_exit(void)
435 struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
437 if (rdtp->dynticks_nmi_nesting == 0 ||
438 --rdtp->dynticks_nmi_nesting != 0)
440 /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
441 smp_mb__before_atomic_inc(); /* See above. */
442 atomic_inc(&rdtp->dynticks);
443 smp_mb__after_atomic_inc(); /* Force delay to next write. */
444 WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
448 * rcu_irq_enter - inform RCU of entry to hard irq context
450 * If the CPU was idle with dynamic ticks active, this updates the
451 * rdtp->dynticks to let the RCU handling know that the CPU is active.
453 void rcu_irq_enter(void)
459 * rcu_irq_exit - inform RCU of exit from hard irq context
461 * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
462 * to put let the RCU handling be aware that the CPU is going back to idle
465 void rcu_irq_exit(void)
473 * Snapshot the specified CPU's dynticks counter so that we can later
474 * credit them with an implicit quiescent state. Return 1 if this CPU
475 * is in dynticks idle mode, which is an extended quiescent state.
477 static int dyntick_save_progress_counter(struct rcu_data *rdp)
479 rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
484 * Return true if the specified CPU has passed through a quiescent
485 * state by virtue of being in or having passed through an dynticks
486 * idle state since the last call to dyntick_save_progress_counter()
489 static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
494 curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
495 snap = (unsigned int)rdp->dynticks_snap;
498 * If the CPU passed through or entered a dynticks idle phase with
499 * no active irq/NMI handlers, then we can safely pretend that the CPU
500 * already acknowledged the request to pass through a quiescent
501 * state. Either way, that CPU cannot possibly be in an RCU
502 * read-side critical section that started before the beginning
503 * of the current RCU grace period.
505 if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
506 trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
511 /* Go check for the CPU being offline. */
512 return rcu_implicit_offline_qs(rdp);
515 #endif /* #ifdef CONFIG_SMP */
517 #else /* #ifdef CONFIG_NO_HZ */
521 static int dyntick_save_progress_counter(struct rcu_data *rdp)
526 static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
528 return rcu_implicit_offline_qs(rdp);
531 #endif /* #ifdef CONFIG_SMP */
533 #endif /* #else #ifdef CONFIG_NO_HZ */
535 int rcu_cpu_stall_suppress __read_mostly;
537 static void record_gp_stall_check_time(struct rcu_state *rsp)
539 rsp->gp_start = jiffies;
540 rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
543 static void print_other_cpu_stall(struct rcu_state *rsp)
548 struct rcu_node *rnp = rcu_get_root(rsp);
550 /* Only let one CPU complain about others per time interval. */
552 raw_spin_lock_irqsave(&rnp->lock, flags);
553 delta = jiffies - rsp->jiffies_stall;
554 if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) {
555 raw_spin_unlock_irqrestore(&rnp->lock, flags);
558 rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
561 * Now rat on any tasks that got kicked up to the root rcu_node
562 * due to CPU offlining.
564 rcu_print_task_stall(rnp);
565 raw_spin_unlock_irqrestore(&rnp->lock, flags);
568 * OK, time to rat on our buddy...
569 * See Documentation/RCU/stallwarn.txt for info on how to debug
570 * RCU CPU stall warnings.
572 printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {",
574 rcu_for_each_leaf_node(rsp, rnp) {
575 raw_spin_lock_irqsave(&rnp->lock, flags);
576 rcu_print_task_stall(rnp);
577 raw_spin_unlock_irqrestore(&rnp->lock, flags);
578 if (rnp->qsmask == 0)
580 for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
581 if (rnp->qsmask & (1UL << cpu))
582 printk(" %d", rnp->grplo + cpu);
584 printk("} (detected by %d, t=%ld jiffies)\n",
585 smp_processor_id(), (long)(jiffies - rsp->gp_start));
586 trigger_all_cpu_backtrace();
588 /* If so configured, complain about tasks blocking the grace period. */
590 rcu_print_detail_task_stall(rsp);
592 force_quiescent_state(rsp, 0); /* Kick them all. */
595 static void print_cpu_stall(struct rcu_state *rsp)
598 struct rcu_node *rnp = rcu_get_root(rsp);
601 * OK, time to rat on ourselves...
602 * See Documentation/RCU/stallwarn.txt for info on how to debug
603 * RCU CPU stall warnings.
605 printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n",
606 rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
607 trigger_all_cpu_backtrace();
609 raw_spin_lock_irqsave(&rnp->lock, flags);
610 if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
612 jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
613 raw_spin_unlock_irqrestore(&rnp->lock, flags);
615 set_need_resched(); /* kick ourselves to get things going. */
618 static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
622 struct rcu_node *rnp;
624 if (rcu_cpu_stall_suppress)
626 j = ACCESS_ONCE(jiffies);
627 js = ACCESS_ONCE(rsp->jiffies_stall);
629 if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
631 /* We haven't checked in, so go dump stack. */
632 print_cpu_stall(rsp);
634 } else if (rcu_gp_in_progress(rsp) &&
635 ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
637 /* They had a few time units to dump stack, so complain. */
638 print_other_cpu_stall(rsp);
642 static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
644 rcu_cpu_stall_suppress = 1;
649 * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
651 * Set the stall-warning timeout way off into the future, thus preventing
652 * any RCU CPU stall-warning messages from appearing in the current set of
655 * The caller must disable hard irqs.
657 void rcu_cpu_stall_reset(void)
659 rcu_sched_state.jiffies_stall = jiffies + ULONG_MAX / 2;
660 rcu_bh_state.jiffies_stall = jiffies + ULONG_MAX / 2;
661 rcu_preempt_stall_reset();
664 static struct notifier_block rcu_panic_block = {
665 .notifier_call = rcu_panic,
668 static void __init check_cpu_stall_init(void)
670 atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
674 * Update CPU-local rcu_data state to record the newly noticed grace period.
675 * This is used both when we started the grace period and when we notice
676 * that someone else started the grace period. The caller must hold the
677 * ->lock of the leaf rcu_node structure corresponding to the current CPU,
678 * and must have irqs disabled.
680 static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
682 if (rdp->gpnum != rnp->gpnum) {
684 * If the current grace period is waiting for this CPU,
685 * set up to detect a quiescent state, otherwise don't
686 * go looking for one.
688 rdp->gpnum = rnp->gpnum;
689 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
690 if (rnp->qsmask & rdp->grpmask) {
692 rdp->passed_quiesce = 0;
698 static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
701 struct rcu_node *rnp;
703 local_irq_save(flags);
705 if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */
706 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
707 local_irq_restore(flags);
710 __note_new_gpnum(rsp, rnp, rdp);
711 raw_spin_unlock_irqrestore(&rnp->lock, flags);
715 * Did someone else start a new RCU grace period start since we last
716 * checked? Update local state appropriately if so. Must be called
717 * on the CPU corresponding to rdp.
720 check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
725 local_irq_save(flags);
726 if (rdp->gpnum != rsp->gpnum) {
727 note_new_gpnum(rsp, rdp);
730 local_irq_restore(flags);
735 * Advance this CPU's callbacks, but only if the current grace period
736 * has ended. This may be called only from the CPU to whom the rdp
737 * belongs. In addition, the corresponding leaf rcu_node structure's
738 * ->lock must be held by the caller, with irqs disabled.
741 __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
743 /* Did another grace period end? */
744 if (rdp->completed != rnp->completed) {
746 /* Advance callbacks. No harm if list empty. */
747 rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
748 rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
749 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
751 /* Remember that we saw this grace-period completion. */
752 rdp->completed = rnp->completed;
753 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
756 * If we were in an extended quiescent state, we may have
757 * missed some grace periods that others CPUs handled on
758 * our behalf. Catch up with this state to avoid noting
759 * spurious new grace periods. If another grace period
760 * has started, then rnp->gpnum will have advanced, so
761 * we will detect this later on.
763 if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
764 rdp->gpnum = rdp->completed;
767 * If RCU does not need a quiescent state from this CPU,
768 * then make sure that this CPU doesn't go looking for one.
770 if ((rnp->qsmask & rdp->grpmask) == 0)
776 * Advance this CPU's callbacks, but only if the current grace period
777 * has ended. This may be called only from the CPU to whom the rdp
781 rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
784 struct rcu_node *rnp;
786 local_irq_save(flags);
788 if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */
789 !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */
790 local_irq_restore(flags);
793 __rcu_process_gp_end(rsp, rnp, rdp);
794 raw_spin_unlock_irqrestore(&rnp->lock, flags);
798 * Do per-CPU grace-period initialization for running CPU. The caller
799 * must hold the lock of the leaf rcu_node structure corresponding to
803 rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
805 /* Prior grace period ended, so advance callbacks for current CPU. */
806 __rcu_process_gp_end(rsp, rnp, rdp);
809 * Because this CPU just now started the new grace period, we know
810 * that all of its callbacks will be covered by this upcoming grace
811 * period, even the ones that were registered arbitrarily recently.
812 * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
814 * Other CPUs cannot be sure exactly when the grace period started.
815 * Therefore, their recently registered callbacks must pass through
816 * an additional RCU_NEXT_READY stage, so that they will be handled
817 * by the next RCU grace period.
819 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
820 rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
822 /* Set state so that this CPU will detect the next quiescent state. */
823 __note_new_gpnum(rsp, rnp, rdp);
827 * Start a new RCU grace period if warranted, re-initializing the hierarchy
828 * in preparation for detecting the next grace period. The caller must hold
829 * the root node's ->lock, which is released before return. Hard irqs must
833 rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
834 __releases(rcu_get_root(rsp)->lock)
836 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
837 struct rcu_node *rnp = rcu_get_root(rsp);
839 if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
840 if (cpu_needs_another_gp(rsp, rdp))
841 rsp->fqs_need_gp = 1;
842 if (rnp->completed == rsp->completed) {
843 raw_spin_unlock_irqrestore(&rnp->lock, flags);
846 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
849 * Propagate new ->completed value to rcu_node structures
850 * so that other CPUs don't have to wait until the start
851 * of the next grace period to process their callbacks.
853 rcu_for_each_node_breadth_first(rsp, rnp) {
854 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
855 rnp->completed = rsp->completed;
856 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
858 local_irq_restore(flags);
862 /* Advance to a new grace period and initialize state. */
864 trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
865 WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
866 rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
867 rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
868 record_gp_stall_check_time(rsp);
870 /* Special-case the common single-level case. */
871 if (NUM_RCU_NODES == 1) {
872 rcu_preempt_check_blocked_tasks(rnp);
873 rnp->qsmask = rnp->qsmaskinit;
874 rnp->gpnum = rsp->gpnum;
875 rnp->completed = rsp->completed;
876 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
877 rcu_start_gp_per_cpu(rsp, rnp, rdp);
878 rcu_preempt_boost_start_gp(rnp);
879 trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
880 rnp->level, rnp->grplo,
881 rnp->grphi, rnp->qsmask);
882 raw_spin_unlock_irqrestore(&rnp->lock, flags);
886 raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
889 /* Exclude any concurrent CPU-hotplug operations. */
890 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
893 * Set the quiescent-state-needed bits in all the rcu_node
894 * structures for all currently online CPUs in breadth-first
895 * order, starting from the root rcu_node structure. This
896 * operation relies on the layout of the hierarchy within the
897 * rsp->node[] array. Note that other CPUs will access only
898 * the leaves of the hierarchy, which still indicate that no
899 * grace period is in progress, at least until the corresponding
900 * leaf node has been initialized. In addition, we have excluded
901 * CPU-hotplug operations.
903 * Note that the grace period cannot complete until we finish
904 * the initialization process, as there will be at least one
905 * qsmask bit set in the root node until that time, namely the
906 * one corresponding to this CPU, due to the fact that we have
909 rcu_for_each_node_breadth_first(rsp, rnp) {
910 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
911 rcu_preempt_check_blocked_tasks(rnp);
912 rnp->qsmask = rnp->qsmaskinit;
913 rnp->gpnum = rsp->gpnum;
914 rnp->completed = rsp->completed;
915 if (rnp == rdp->mynode)
916 rcu_start_gp_per_cpu(rsp, rnp, rdp);
917 rcu_preempt_boost_start_gp(rnp);
918 trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
919 rnp->level, rnp->grplo,
920 rnp->grphi, rnp->qsmask);
921 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
924 rnp = rcu_get_root(rsp);
925 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
926 rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
927 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
928 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
932 * Report a full set of quiescent states to the specified rcu_state
933 * data structure. This involves cleaning up after the prior grace
934 * period and letting rcu_start_gp() start up the next grace period
935 * if one is needed. Note that the caller must hold rnp->lock, as
936 * required by rcu_start_gp(), which will release it.
938 static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
939 __releases(rcu_get_root(rsp)->lock)
941 unsigned long gp_duration;
943 WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
946 * Ensure that all grace-period and pre-grace-period activity
947 * is seen before the assignment to rsp->completed.
949 smp_mb(); /* See above block comment. */
950 gp_duration = jiffies - rsp->gp_start;
951 if (gp_duration > rsp->gp_max)
952 rsp->gp_max = gp_duration;
953 rsp->completed = rsp->gpnum;
954 trace_rcu_grace_period(rsp->name, rsp->completed, "end");
955 rsp->signaled = RCU_GP_IDLE;
956 rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
960 * Similar to rcu_report_qs_rdp(), for which it is a helper function.
961 * Allows quiescent states for a group of CPUs to be reported at one go
962 * to the specified rcu_node structure, though all the CPUs in the group
963 * must be represented by the same rcu_node structure (which need not be
964 * a leaf rcu_node structure, though it often will be). That structure's
965 * lock must be held upon entry, and it is released before return.
968 rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
969 struct rcu_node *rnp, unsigned long flags)
970 __releases(rnp->lock)
972 struct rcu_node *rnp_c;
974 /* Walk up the rcu_node hierarchy. */
976 if (!(rnp->qsmask & mask)) {
978 /* Our bit has already been cleared, so done. */
979 raw_spin_unlock_irqrestore(&rnp->lock, flags);
982 rnp->qsmask &= ~mask;
983 trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
984 mask, rnp->qsmask, rnp->level,
985 rnp->grplo, rnp->grphi,
987 if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
989 /* Other bits still set at this level, so done. */
990 raw_spin_unlock_irqrestore(&rnp->lock, flags);
994 if (rnp->parent == NULL) {
996 /* No more levels. Exit loop holding root lock. */
1000 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1003 raw_spin_lock_irqsave(&rnp->lock, flags);
1004 WARN_ON_ONCE(rnp_c->qsmask);
1008 * Get here if we are the last CPU to pass through a quiescent
1009 * state for this grace period. Invoke rcu_report_qs_rsp()
1010 * to clean up and start the next grace period if one is needed.
1012 rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
1016 * Record a quiescent state for the specified CPU to that CPU's rcu_data
1017 * structure. This must be either called from the specified CPU, or
1018 * called when the specified CPU is known to be offline (and when it is
1019 * also known that no other CPU is concurrently trying to help the offline
1020 * CPU). The lastcomp argument is used to make sure we are still in the
1021 * grace period of interest. We don't want to end the current grace period
1022 * based on quiescent states detected in an earlier grace period!
1025 rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
1027 unsigned long flags;
1029 struct rcu_node *rnp;
1032 raw_spin_lock_irqsave(&rnp->lock, flags);
1033 if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
1036 * The grace period in which this quiescent state was
1037 * recorded has ended, so don't report it upwards.
1038 * We will instead need a new quiescent state that lies
1039 * within the current grace period.
1041 rdp->passed_quiesce = 0; /* need qs for new gp. */
1042 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1045 mask = rdp->grpmask;
1046 if ((rnp->qsmask & mask) == 0) {
1047 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1049 rdp->qs_pending = 0;
1052 * This GP can't end until cpu checks in, so all of our
1053 * callbacks can be processed during the next GP.
1055 rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
1057 rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
1062 * Check to see if there is a new grace period of which this CPU
1063 * is not yet aware, and if so, set up local rcu_data state for it.
1064 * Otherwise, see if this CPU has just passed through its first
1065 * quiescent state for this grace period, and record that fact if so.
1068 rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
1070 /* If there is now a new grace period, record and return. */
1071 if (check_for_new_grace_period(rsp, rdp))
1075 * Does this CPU still need to do its part for current grace period?
1076 * If no, return and let the other CPUs do their part as well.
1078 if (!rdp->qs_pending)
1082 * Was there a quiescent state since the beginning of the grace
1083 * period? If no, then exit and wait for the next call.
1085 if (!rdp->passed_quiesce)
1089 * Tell RCU we are done (but rcu_report_qs_rdp() will be the
1092 rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
1095 #ifdef CONFIG_HOTPLUG_CPU
1098 * Move a dying CPU's RCU callbacks to online CPU's callback list.
1099 * Synchronization is not required because this function executes
1100 * in stop_machine() context.
1102 static void rcu_send_cbs_to_online(struct rcu_state *rsp)
1105 /* current DYING CPU is cleared in the cpu_online_mask */
1106 int receive_cpu = cpumask_any(cpu_online_mask);
1107 struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
1108 struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu);
1110 if (rdp->nxtlist == NULL)
1111 return; /* irqs disabled, so comparison is stable. */
1113 *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
1114 receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
1115 receive_rdp->qlen += rdp->qlen;
1116 receive_rdp->n_cbs_adopted += rdp->qlen;
1117 rdp->n_cbs_orphaned += rdp->qlen;
1119 rdp->nxtlist = NULL;
1120 for (i = 0; i < RCU_NEXT_SIZE; i++)
1121 rdp->nxttail[i] = &rdp->nxtlist;
1126 * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
1127 * and move all callbacks from the outgoing CPU to the current one.
1128 * There can only be one CPU hotplug operation at a time, so no other
1129 * CPU can be attempting to update rcu_cpu_kthread_task.
1131 static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
1133 unsigned long flags;
1135 int need_report = 0;
1136 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
1137 struct rcu_node *rnp;
1139 rcu_stop_cpu_kthread(cpu);
1141 /* Exclude any attempts to start a new grace period. */
1142 raw_spin_lock_irqsave(&rsp->onofflock, flags);
1144 /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
1145 rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */
1146 mask = rdp->grpmask; /* rnp->grplo is constant. */
1148 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
1149 rnp->qsmaskinit &= ~mask;
1150 if (rnp->qsmaskinit != 0) {
1151 if (rnp != rdp->mynode)
1152 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
1154 trace_rcu_grace_period(rsp->name,
1156 !!(rnp->qsmask & mask),
1160 if (rnp == rdp->mynode) {
1161 trace_rcu_grace_period(rsp->name,
1163 !!(rnp->qsmask & mask),
1165 need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp);
1167 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
1168 mask = rnp->grpmask;
1170 } while (rnp != NULL);
1173 * We still hold the leaf rcu_node structure lock here, and
1174 * irqs are still disabled. The reason for this subterfuge is
1175 * because invoking rcu_report_unblock_qs_rnp() with ->onofflock
1176 * held leads to deadlock.
1178 raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
1180 if (need_report & RCU_OFL_TASKS_NORM_GP)
1181 rcu_report_unblock_qs_rnp(rnp, flags);
1183 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1184 if (need_report & RCU_OFL_TASKS_EXP_GP)
1185 rcu_report_exp_rnp(rsp, rnp);
1186 rcu_node_kthread_setaffinity(rnp, -1);
1190 * Remove the specified CPU from the RCU hierarchy and move any pending
1191 * callbacks that it might have to the current CPU. This code assumes
1192 * that at least one CPU in the system will remain running at all times.
1193 * Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
1195 static void rcu_offline_cpu(int cpu)
1197 __rcu_offline_cpu(cpu, &rcu_sched_state);
1198 __rcu_offline_cpu(cpu, &rcu_bh_state);
1199 rcu_preempt_offline_cpu(cpu);
1202 #else /* #ifdef CONFIG_HOTPLUG_CPU */
1204 static void rcu_send_cbs_to_online(struct rcu_state *rsp)
1208 static void rcu_offline_cpu(int cpu)
1212 #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
1215 * Invoke any RCU callbacks that have made it to the end of their grace
1216 * period. Thottle as specified by rdp->blimit.
1218 static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
1220 unsigned long flags;
1221 struct rcu_head *next, *list, **tail;
1224 /* If no callbacks are ready, just return.*/
1225 if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
1226 trace_rcu_batch_start(rsp->name, 0, 0);
1227 trace_rcu_batch_end(rsp->name, 0);
1232 * Extract the list of ready callbacks, disabling to prevent
1233 * races with call_rcu() from interrupt handlers.
1235 local_irq_save(flags);
1237 trace_rcu_batch_start(rsp->name, rdp->qlen, bl);
1238 list = rdp->nxtlist;
1239 rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
1240 *rdp->nxttail[RCU_DONE_TAIL] = NULL;
1241 tail = rdp->nxttail[RCU_DONE_TAIL];
1242 for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
1243 if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
1244 rdp->nxttail[count] = &rdp->nxtlist;
1245 local_irq_restore(flags);
1247 /* Invoke callbacks. */
1252 debug_rcu_head_unqueue(list);
1253 __rcu_reclaim(rsp->name, list);
1259 local_irq_save(flags);
1260 trace_rcu_batch_end(rsp->name, count);
1262 /* Update count, and requeue any remaining callbacks. */
1264 rdp->n_cbs_invoked += count;
1266 *tail = rdp->nxtlist;
1267 rdp->nxtlist = list;
1268 for (count = 0; count < RCU_NEXT_SIZE; count++)
1269 if (&rdp->nxtlist == rdp->nxttail[count])
1270 rdp->nxttail[count] = tail;
1275 /* Reinstate batch limit if we have worked down the excess. */
1276 if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
1277 rdp->blimit = blimit;
1279 /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
1280 if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) {
1281 rdp->qlen_last_fqs_check = 0;
1282 rdp->n_force_qs_snap = rsp->n_force_qs;
1283 } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark)
1284 rdp->qlen_last_fqs_check = rdp->qlen;
1286 local_irq_restore(flags);
1288 /* Re-invoke RCU core processing if there are callbacks remaining. */
1289 if (cpu_has_callbacks_ready_to_invoke(rdp))
1294 * Check to see if this CPU is in a non-context-switch quiescent state
1295 * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
1296 * Also schedule RCU core processing.
1298 * This function must be called with hardirqs disabled. It is normally
1299 * invoked from the scheduling-clock interrupt. If rcu_pending returns
1300 * false, there is no point in invoking rcu_check_callbacks().
1302 void rcu_check_callbacks(int cpu, int user)
1304 trace_rcu_utilization("Start scheduler-tick");
1306 (idle_cpu(cpu) && rcu_scheduler_active &&
1307 !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
1310 * Get here if this CPU took its interrupt from user
1311 * mode or from the idle loop, and if this is not a
1312 * nested interrupt. In this case, the CPU is in
1313 * a quiescent state, so note it.
1315 * No memory barrier is required here because both
1316 * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
1317 * variables that other CPUs neither access nor modify,
1318 * at least not while the corresponding CPU is online.
1324 } else if (!in_softirq()) {
1327 * Get here if this CPU did not take its interrupt from
1328 * softirq, in other words, if it is not interrupting
1329 * a rcu_bh read-side critical section. This is an _bh
1330 * critical section, so note it.
1335 rcu_preempt_check_callbacks(cpu);
1336 if (rcu_pending(cpu))
1338 trace_rcu_utilization("End scheduler-tick");
1344 * Scan the leaf rcu_node structures, processing dyntick state for any that
1345 * have not yet encountered a quiescent state, using the function specified.
1346 * Also initiate boosting for any threads blocked on the root rcu_node.
1348 * The caller must have suppressed start of new grace periods.
1350 static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *))
1354 unsigned long flags;
1356 struct rcu_node *rnp;
1358 rcu_for_each_leaf_node(rsp, rnp) {
1360 raw_spin_lock_irqsave(&rnp->lock, flags);
1361 if (!rcu_gp_in_progress(rsp)) {
1362 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1365 if (rnp->qsmask == 0) {
1366 rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
1371 for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
1372 if ((rnp->qsmask & bit) != 0 &&
1373 f(per_cpu_ptr(rsp->rda, cpu)))
1378 /* rcu_report_qs_rnp() releases rnp->lock. */
1379 rcu_report_qs_rnp(mask, rsp, rnp, flags);
1382 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1384 rnp = rcu_get_root(rsp);
1385 if (rnp->qsmask == 0) {
1386 raw_spin_lock_irqsave(&rnp->lock, flags);
1387 rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
1392 * Force quiescent states on reluctant CPUs, and also detect which
1393 * CPUs are in dyntick-idle mode.
1395 static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1397 unsigned long flags;
1398 struct rcu_node *rnp = rcu_get_root(rsp);
1400 trace_rcu_utilization("Start fqs");
1401 if (!rcu_gp_in_progress(rsp)) {
1402 trace_rcu_utilization("End fqs");
1403 return; /* No grace period in progress, nothing to force. */
1405 if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
1406 rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
1407 trace_rcu_utilization("End fqs");
1408 return; /* Someone else is already on the job. */
1410 if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
1411 goto unlock_fqs_ret; /* no emergency and done recently. */
1413 raw_spin_lock(&rnp->lock); /* irqs already disabled */
1414 rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
1415 if(!rcu_gp_in_progress(rsp)) {
1416 rsp->n_force_qs_ngp++;
1417 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
1418 goto unlock_fqs_ret; /* no GP in progress, time updated. */
1420 rsp->fqs_active = 1;
1421 switch (rsp->signaled) {
1425 break; /* grace period idle or initializing, ignore. */
1427 case RCU_SAVE_DYNTICK:
1428 if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
1429 break; /* So gcc recognizes the dead code. */
1431 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
1433 /* Record dyntick-idle state. */
1434 force_qs_rnp(rsp, dyntick_save_progress_counter);
1435 raw_spin_lock(&rnp->lock); /* irqs already disabled */
1436 if (rcu_gp_in_progress(rsp))
1437 rsp->signaled = RCU_FORCE_QS;
1442 /* Check dyntick-idle state, send IPI to laggarts. */
1443 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
1444 force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
1446 /* Leave state in case more forcing is required. */
1448 raw_spin_lock(&rnp->lock); /* irqs already disabled */
1451 rsp->fqs_active = 0;
1452 if (rsp->fqs_need_gp) {
1453 raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
1454 rsp->fqs_need_gp = 0;
1455 rcu_start_gp(rsp, flags); /* releases rnp->lock */
1456 trace_rcu_utilization("End fqs");
1459 raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
1461 raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
1462 trace_rcu_utilization("End fqs");
1465 #else /* #ifdef CONFIG_SMP */
1467 static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
1472 #endif /* #else #ifdef CONFIG_SMP */
1475 * This does the RCU core processing work for the specified rcu_state
1476 * and rcu_data structures. This may be called only from the CPU to
1477 * whom the rdp belongs.
1480 __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
1482 unsigned long flags;
1484 WARN_ON_ONCE(rdp->beenonline == 0);
1487 * If an RCU GP has gone long enough, go check for dyntick
1488 * idle CPUs and, if needed, send resched IPIs.
1490 if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
1491 force_quiescent_state(rsp, 1);
1494 * Advance callbacks in response to end of earlier grace
1495 * period that some other CPU ended.
1497 rcu_process_gp_end(rsp, rdp);
1499 /* Update RCU state based on any recent quiescent states. */
1500 rcu_check_quiescent_state(rsp, rdp);
1502 /* Does this CPU require a not-yet-started grace period? */
1503 if (cpu_needs_another_gp(rsp, rdp)) {
1504 raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
1505 rcu_start_gp(rsp, flags); /* releases above lock */
1508 /* If there are callbacks ready, invoke them. */
1509 if (cpu_has_callbacks_ready_to_invoke(rdp))
1510 invoke_rcu_callbacks(rsp, rdp);
1514 * Do RCU core processing for the current CPU.
1516 static void rcu_process_callbacks(struct softirq_action *unused)
1518 trace_rcu_utilization("Start RCU core");
1519 __rcu_process_callbacks(&rcu_sched_state,
1520 &__get_cpu_var(rcu_sched_data));
1521 __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
1522 rcu_preempt_process_callbacks();
1524 /* If we are last CPU on way to dyntick-idle mode, accelerate it. */
1525 rcu_needs_cpu_flush();
1526 trace_rcu_utilization("End RCU core");
1530 * Schedule RCU callback invocation. If the specified type of RCU
1531 * does not support RCU priority boosting, just do a direct call,
1532 * otherwise wake up the per-CPU kernel kthread. Note that because we
1533 * are running on the current CPU with interrupts disabled, the
1534 * rcu_cpu_kthread_task cannot disappear out from under us.
1536 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
1538 if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
1540 if (likely(!rsp->boost)) {
1541 rcu_do_batch(rsp, rdp);
1544 invoke_rcu_callbacks_kthread();
1547 static void invoke_rcu_core(void)
1549 raise_softirq(RCU_SOFTIRQ);
1553 __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
1554 struct rcu_state *rsp)
1556 unsigned long flags;
1557 struct rcu_data *rdp;
1559 debug_rcu_head_queue(head);
1563 smp_mb(); /* Ensure RCU update seen before callback registry. */
1566 * Opportunistically note grace-period endings and beginnings.
1567 * Note that we might see a beginning right after we see an
1568 * end, but never vice versa, since this CPU has to pass through
1569 * a quiescent state betweentimes.
1571 local_irq_save(flags);
1572 rdp = this_cpu_ptr(rsp->rda);
1574 /* Add the callback to our list. */
1575 *rdp->nxttail[RCU_NEXT_TAIL] = head;
1576 rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
1579 if (__is_kfree_rcu_offset((unsigned long)func))
1580 trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
1583 trace_rcu_callback(rsp->name, head, rdp->qlen);
1585 /* If interrupts were disabled, don't dive into RCU core. */
1586 if (irqs_disabled_flags(flags)) {
1587 local_irq_restore(flags);
1592 * Force the grace period if too many callbacks or too long waiting.
1593 * Enforce hysteresis, and don't invoke force_quiescent_state()
1594 * if some other CPU has recently done so. Also, don't bother
1595 * invoking force_quiescent_state() if the newly enqueued callback
1596 * is the only one waiting for a grace period to complete.
1598 if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
1600 /* Are we ignoring a completed grace period? */
1601 rcu_process_gp_end(rsp, rdp);
1602 check_for_new_grace_period(rsp, rdp);
1604 /* Start a new grace period if one not already started. */
1605 if (!rcu_gp_in_progress(rsp)) {
1606 unsigned long nestflag;
1607 struct rcu_node *rnp_root = rcu_get_root(rsp);
1609 raw_spin_lock_irqsave(&rnp_root->lock, nestflag);
1610 rcu_start_gp(rsp, nestflag); /* rlses rnp_root->lock */
1612 /* Give the grace period a kick. */
1613 rdp->blimit = LONG_MAX;
1614 if (rsp->n_force_qs == rdp->n_force_qs_snap &&
1615 *rdp->nxttail[RCU_DONE_TAIL] != head)
1616 force_quiescent_state(rsp, 0);
1617 rdp->n_force_qs_snap = rsp->n_force_qs;
1618 rdp->qlen_last_fqs_check = rdp->qlen;
1620 } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
1621 force_quiescent_state(rsp, 1);
1622 local_irq_restore(flags);
1626 * Queue an RCU-sched callback for invocation after a grace period.
1628 void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
1630 __call_rcu(head, func, &rcu_sched_state);
1632 EXPORT_SYMBOL_GPL(call_rcu_sched);
1635 * Queue an RCU for invocation after a quicker grace period.
1637 void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
1639 __call_rcu(head, func, &rcu_bh_state);
1641 EXPORT_SYMBOL_GPL(call_rcu_bh);
1644 * synchronize_sched - wait until an rcu-sched grace period has elapsed.
1646 * Control will return to the caller some time after a full rcu-sched
1647 * grace period has elapsed, in other words after all currently executing
1648 * rcu-sched read-side critical sections have completed. These read-side
1649 * critical sections are delimited by rcu_read_lock_sched() and
1650 * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(),
1651 * local_irq_disable(), and so on may be used in place of
1652 * rcu_read_lock_sched().
1654 * This means that all preempt_disable code sequences, including NMI and
1655 * hardware-interrupt handlers, in progress on entry will have completed
1656 * before this primitive returns. However, this does not guarantee that
1657 * softirq handlers will have completed, since in some kernels, these
1658 * handlers can run in process context, and can block.
1660 * This primitive provides the guarantees made by the (now removed)
1661 * synchronize_kernel() API. In contrast, synchronize_rcu() only
1662 * guarantees that rcu_read_lock() sections will have completed.
1663 * In "classic RCU", these two guarantees happen to be one and
1664 * the same, but can differ in realtime RCU implementations.
1666 void synchronize_sched(void)
1668 if (rcu_blocking_is_gp())
1670 wait_rcu_gp(call_rcu_sched);
1672 EXPORT_SYMBOL_GPL(synchronize_sched);
1675 * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed.
1677 * Control will return to the caller some time after a full rcu_bh grace
1678 * period has elapsed, in other words after all currently executing rcu_bh
1679 * read-side critical sections have completed. RCU read-side critical
1680 * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(),
1681 * and may be nested.
1683 void synchronize_rcu_bh(void)
1685 if (rcu_blocking_is_gp())
1687 wait_rcu_gp(call_rcu_bh);
1689 EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
1692 * Check to see if there is any immediate RCU-related work to be done
1693 * by the current CPU, for the specified type of RCU, returning 1 if so.
1694 * The checks are in order of increasing expense: checks that can be
1695 * carried out against CPU-local state are performed first. However,
1696 * we must check for CPU stalls first, else we might not get a chance.
1698 static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
1700 struct rcu_node *rnp = rdp->mynode;
1702 rdp->n_rcu_pending++;
1704 /* Check for CPU stalls, if enabled. */
1705 check_cpu_stall(rsp, rdp);
1707 /* Is the RCU core waiting for a quiescent state from this CPU? */
1708 if (rdp->qs_pending && !rdp->passed_quiesce) {
1711 * If force_quiescent_state() coming soon and this CPU
1712 * needs a quiescent state, and this is either RCU-sched
1713 * or RCU-bh, force a local reschedule.
1715 rdp->n_rp_qs_pending++;
1716 if (!rdp->preemptible &&
1717 ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
1720 } else if (rdp->qs_pending && rdp->passed_quiesce) {
1721 rdp->n_rp_report_qs++;
1725 /* Does this CPU have callbacks ready to invoke? */
1726 if (cpu_has_callbacks_ready_to_invoke(rdp)) {
1727 rdp->n_rp_cb_ready++;
1731 /* Has RCU gone idle with this CPU needing another grace period? */
1732 if (cpu_needs_another_gp(rsp, rdp)) {
1733 rdp->n_rp_cpu_needs_gp++;
1737 /* Has another RCU grace period completed? */
1738 if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */
1739 rdp->n_rp_gp_completed++;
1743 /* Has a new RCU grace period started? */
1744 if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */
1745 rdp->n_rp_gp_started++;
1749 /* Has an RCU GP gone long enough to send resched IPIs &c? */
1750 if (rcu_gp_in_progress(rsp) &&
1751 ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
1752 rdp->n_rp_need_fqs++;
1757 rdp->n_rp_need_nothing++;
1762 * Check to see if there is any immediate RCU-related work to be done
1763 * by the current CPU, returning 1 if so. This function is part of the
1764 * RCU implementation; it is -not- an exported member of the RCU API.
1766 static int rcu_pending(int cpu)
1768 return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
1769 __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
1770 rcu_preempt_pending(cpu);
1774 * Check to see if any future RCU-related work will need to be done
1775 * by the current CPU, even if none need be done immediately, returning
1778 static int rcu_needs_cpu_quick_check(int cpu)
1780 /* RCU callbacks either ready or pending? */
1781 return per_cpu(rcu_sched_data, cpu).nxtlist ||
1782 per_cpu(rcu_bh_data, cpu).nxtlist ||
1783 rcu_preempt_needs_cpu(cpu);
1786 static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
1787 static atomic_t rcu_barrier_cpu_count;
1788 static DEFINE_MUTEX(rcu_barrier_mutex);
1789 static struct completion rcu_barrier_completion;
1791 static void rcu_barrier_callback(struct rcu_head *notused)
1793 if (atomic_dec_and_test(&rcu_barrier_cpu_count))
1794 complete(&rcu_barrier_completion);
1798 * Called with preemption disabled, and from cross-cpu IRQ context.
1800 static void rcu_barrier_func(void *type)
1802 int cpu = smp_processor_id();
1803 struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu);
1804 void (*call_rcu_func)(struct rcu_head *head,
1805 void (*func)(struct rcu_head *head));
1807 atomic_inc(&rcu_barrier_cpu_count);
1808 call_rcu_func = type;
1809 call_rcu_func(head, rcu_barrier_callback);
1813 * Orchestrate the specified type of RCU barrier, waiting for all
1814 * RCU callbacks of the specified type to complete.
1816 static void _rcu_barrier(struct rcu_state *rsp,
1817 void (*call_rcu_func)(struct rcu_head *head,
1818 void (*func)(struct rcu_head *head)))
1820 BUG_ON(in_interrupt());
1821 /* Take mutex to serialize concurrent rcu_barrier() requests. */
1822 mutex_lock(&rcu_barrier_mutex);
1823 init_completion(&rcu_barrier_completion);
1825 * Initialize rcu_barrier_cpu_count to 1, then invoke
1826 * rcu_barrier_func() on each CPU, so that each CPU also has
1827 * incremented rcu_barrier_cpu_count. Only then is it safe to
1828 * decrement rcu_barrier_cpu_count -- otherwise the first CPU
1829 * might complete its grace period before all of the other CPUs
1830 * did their increment, causing this function to return too
1831 * early. Note that on_each_cpu() disables irqs, which prevents
1832 * any CPUs from coming online or going offline until each online
1833 * CPU has queued its RCU-barrier callback.
1835 atomic_set(&rcu_barrier_cpu_count, 1);
1836 on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1);
1837 if (atomic_dec_and_test(&rcu_barrier_cpu_count))
1838 complete(&rcu_barrier_completion);
1839 wait_for_completion(&rcu_barrier_completion);
1840 mutex_unlock(&rcu_barrier_mutex);
1844 * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete.
1846 void rcu_barrier_bh(void)
1848 _rcu_barrier(&rcu_bh_state, call_rcu_bh);
1850 EXPORT_SYMBOL_GPL(rcu_barrier_bh);
1853 * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks.
1855 void rcu_barrier_sched(void)
1857 _rcu_barrier(&rcu_sched_state, call_rcu_sched);
1859 EXPORT_SYMBOL_GPL(rcu_barrier_sched);
1862 * Do boot-time initialization of a CPU's per-CPU RCU data.
1865 rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
1867 unsigned long flags;
1869 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
1870 struct rcu_node *rnp = rcu_get_root(rsp);
1872 /* Set up local state, ensuring consistent view of global state. */
1873 raw_spin_lock_irqsave(&rnp->lock, flags);
1874 rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
1875 rdp->nxtlist = NULL;
1876 for (i = 0; i < RCU_NEXT_SIZE; i++)
1877 rdp->nxttail[i] = &rdp->nxtlist;
1880 rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
1881 #endif /* #ifdef CONFIG_NO_HZ */
1884 raw_spin_unlock_irqrestore(&rnp->lock, flags);
1888 * Initialize a CPU's per-CPU RCU data. Note that only one online or
1889 * offline event can be happening at a given time. Note also that we
1890 * can accept some slop in the rsp->completed access due to the fact
1891 * that this CPU cannot possibly have any RCU callbacks in flight yet.
1893 static void __cpuinit
1894 rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible)
1896 unsigned long flags;
1898 struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
1899 struct rcu_node *rnp = rcu_get_root(rsp);
1901 /* Set up local state, ensuring consistent view of global state. */
1902 raw_spin_lock_irqsave(&rnp->lock, flags);
1903 rdp->passed_quiesce = 0; /* We could be racing with new GP, */
1904 rdp->qs_pending = 1; /* so set up to respond to current GP. */
1905 rdp->beenonline = 1; /* We have now been online. */
1906 rdp->preemptible = preemptible;
1907 rdp->qlen_last_fqs_check = 0;
1908 rdp->n_force_qs_snap = rsp->n_force_qs;
1909 rdp->blimit = blimit;
1910 raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
1913 * A new grace period might start here. If so, we won't be part
1914 * of it, but that is OK, as we are currently in a quiescent state.
1917 /* Exclude any attempts to start a new GP on large systems. */
1918 raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
1920 /* Add CPU to rcu_node bitmasks. */
1922 mask = rdp->grpmask;
1924 /* Exclude any attempts to start a new GP on small systems. */
1925 raw_spin_lock(&rnp->lock); /* irqs already disabled. */
1926 rnp->qsmaskinit |= mask;
1927 mask = rnp->grpmask;
1928 if (rnp == rdp->mynode) {
1929 rdp->gpnum = rnp->completed; /* if GP in progress... */
1930 rdp->completed = rnp->completed;
1931 rdp->passed_quiesce_gpnum = rnp->gpnum - 1;
1932 trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
1934 raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
1936 } while (rnp != NULL && !(rnp->qsmaskinit & mask));
1938 raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
1941 static void __cpuinit rcu_prepare_cpu(int cpu)
1943 rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
1944 rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
1945 rcu_preempt_init_percpu_data(cpu);
1949 * Handle CPU online/offline notification events.
1951 static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
1952 unsigned long action, void *hcpu)
1954 long cpu = (long)hcpu;
1955 struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
1956 struct rcu_node *rnp = rdp->mynode;
1958 trace_rcu_utilization("Start CPU hotplug");
1960 case CPU_UP_PREPARE:
1961 case CPU_UP_PREPARE_FROZEN:
1962 rcu_prepare_cpu(cpu);
1963 rcu_prepare_kthreads(cpu);
1966 case CPU_DOWN_FAILED:
1967 rcu_node_kthread_setaffinity(rnp, -1);
1968 rcu_cpu_kthread_setrt(cpu, 1);
1970 case CPU_DOWN_PREPARE:
1971 rcu_node_kthread_setaffinity(rnp, cpu);
1972 rcu_cpu_kthread_setrt(cpu, 0);
1975 case CPU_DYING_FROZEN:
1977 * The whole machine is "stopped" except this CPU, so we can
1978 * touch any data without introducing corruption. We send the
1979 * dying CPU's callbacks to an arbitrarily chosen online CPU.
1981 rcu_send_cbs_to_online(&rcu_bh_state);
1982 rcu_send_cbs_to_online(&rcu_sched_state);
1983 rcu_preempt_send_cbs_to_online();
1986 case CPU_DEAD_FROZEN:
1987 case CPU_UP_CANCELED:
1988 case CPU_UP_CANCELED_FROZEN:
1989 rcu_offline_cpu(cpu);
1994 trace_rcu_utilization("End CPU hotplug");
1999 * This function is invoked towards the end of the scheduler's initialization
2000 * process. Before this is called, the idle task might contain
2001 * RCU read-side critical sections (during which time, this idle
2002 * task is booting the system). After this function is called, the
2003 * idle tasks are prohibited from containing RCU read-side critical
2004 * sections. This function also enables RCU lockdep checking.
2006 void rcu_scheduler_starting(void)
2008 WARN_ON(num_online_cpus() != 1);
2009 WARN_ON(nr_context_switches() > 0);
2010 rcu_scheduler_active = 1;
2014 * Compute the per-level fanout, either using the exact fanout specified
2015 * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
2017 #ifdef CONFIG_RCU_FANOUT_EXACT
2018 static void __init rcu_init_levelspread(struct rcu_state *rsp)
2022 for (i = NUM_RCU_LVLS - 1; i > 0; i--)
2023 rsp->levelspread[i] = CONFIG_RCU_FANOUT;
2024 rsp->levelspread[0] = RCU_FANOUT_LEAF;
2026 #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
2027 static void __init rcu_init_levelspread(struct rcu_state *rsp)
2034 for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
2035 ccur = rsp->levelcnt[i];
2036 rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
2040 #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
2043 * Helper function for rcu_init() that initializes one rcu_state structure.
2045 static void __init rcu_init_one(struct rcu_state *rsp,
2046 struct rcu_data __percpu *rda)
2048 static char *buf[] = { "rcu_node_level_0",
2051 "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */
2055 struct rcu_node *rnp;
2057 BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
2059 /* Initialize the level-tracking arrays. */
2061 for (i = 1; i < NUM_RCU_LVLS; i++)
2062 rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
2063 rcu_init_levelspread(rsp);
2065 /* Initialize the elements themselves, starting from the leaves. */
2067 for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
2068 cpustride *= rsp->levelspread[i];
2069 rnp = rsp->level[i];
2070 for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
2071 raw_spin_lock_init(&rnp->lock);
2072 lockdep_set_class_and_name(&rnp->lock,
2073 &rcu_node_class[i], buf[i]);
2076 rnp->qsmaskinit = 0;
2077 rnp->grplo = j * cpustride;
2078 rnp->grphi = (j + 1) * cpustride - 1;
2079 if (rnp->grphi >= NR_CPUS)
2080 rnp->grphi = NR_CPUS - 1;
2086 rnp->grpnum = j % rsp->levelspread[i - 1];
2087 rnp->grpmask = 1UL << rnp->grpnum;
2088 rnp->parent = rsp->level[i - 1] +
2089 j / rsp->levelspread[i - 1];
2092 INIT_LIST_HEAD(&rnp->blkd_tasks);
2097 rnp = rsp->level[NUM_RCU_LVLS - 1];
2098 for_each_possible_cpu(i) {
2099 while (i > rnp->grphi)
2101 per_cpu_ptr(rsp->rda, i)->mynode = rnp;
2102 rcu_boot_init_percpu_data(i, rsp);
2106 void __init rcu_init(void)
2110 rcu_bootup_announce();
2111 rcu_init_one(&rcu_sched_state, &rcu_sched_data);
2112 rcu_init_one(&rcu_bh_state, &rcu_bh_data);
2113 __rcu_init_preempt();
2114 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
2117 * We don't need protection against CPU-hotplug here because
2118 * this is called early in boot, before either interrupts
2119 * or the scheduler are operational.
2121 cpu_notifier(rcu_cpu_notify, 0);
2122 for_each_online_cpu(cpu)
2123 rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
2124 check_cpu_stall_init();
2127 #include "rcutree_plugin.h"