2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1991, 1993
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6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
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36 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
42 #include "opt_callout_profiling.h"
46 #include <sys/param.h>
47 #include <sys/systm.h>
49 #include <sys/callout.h>
50 #include <sys/domainset.h>
52 #include <sys/interrupt.h>
53 #include <sys/kernel.h>
55 #include <sys/kthread.h>
57 #include <sys/malloc.h>
58 #include <sys/mutex.h>
60 #include <sys/random.h>
61 #include <sys/sched.h>
63 #include <sys/sleepqueue.h>
64 #include <sys/sysctl.h>
66 #include <sys/unistd.h>
70 #include <ddb/db_sym.h>
71 #include <machine/_inttypes.h>
75 #include <machine/cpu.h>
78 DPCPU_DECLARE(sbintime_t, hardclocktime);
80 SDT_PROVIDER_DEFINE(callout_execute);
81 SDT_PROBE_DEFINE1(callout_execute, , , callout__start, "struct callout *");
82 SDT_PROBE_DEFINE1(callout_execute, , , callout__end, "struct callout *");
84 static void softclock_thread(void *arg);
86 #ifdef CALLOUT_PROFILING
88 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
89 "Average number of items examined per softclock call. Units = 1/1000");
90 static int avg_gcalls;
91 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
92 "Average number of Giant callouts made per softclock call. Units = 1/1000");
93 static int avg_lockcalls;
94 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
95 "Average number of lock callouts made per softclock call. Units = 1/1000");
96 static int avg_mpcalls;
97 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
98 "Average number of MP callouts made per softclock call. Units = 1/1000");
99 static int avg_depth_dir;
100 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
101 "Average number of direct callouts examined per callout_process call. "
103 static int avg_lockcalls_dir;
104 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
105 &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
106 "callout_process call. Units = 1/1000");
107 static int avg_mpcalls_dir;
108 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
109 0, "Average number of MP direct callouts made per callout_process call. "
114 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
115 "Number of entries in callwheel and size of timeout() preallocation");
118 static int pin_default_swi = 1;
119 static int pin_pcpu_swi = 1;
121 static int pin_default_swi = 0;
122 static int pin_pcpu_swi = 0;
125 SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
126 0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
127 SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
128 0, "Pin the per-CPU swis (except PCPU 0, which is also default)");
132 * allocate more timeout table slots when table overflows.
134 static u_int __read_mostly callwheelsize;
135 static u_int __read_mostly callwheelmask;
138 * The callout cpu exec entities represent informations necessary for
139 * describing the state of callouts currently running on the CPU and the ones
140 * necessary for migrating callouts to the new callout cpu. In particular,
141 * the first entry of the array cc_exec_entity holds informations for callout
142 * running in SWI thread context, while the second one holds informations
143 * for callout running directly from hardware interrupt context.
144 * The cached informations are very important for deferring migration when
145 * the migrating callout is already running.
148 struct callout *cc_curr;
149 callout_func_t *cc_drain;
153 callout_func_t *ce_migration_func;
154 void *ce_migration_arg;
155 sbintime_t ce_migration_time;
156 sbintime_t ce_migration_prec;
157 int ce_migration_cpu;
164 * There is one struct callout_cpu per cpu, holding all relevant
165 * state for the callout processing thread on the individual CPU.
168 struct mtx_padalign cc_lock;
169 struct cc_exec cc_exec_entity[2];
170 struct callout *cc_next;
171 struct callout_list *cc_callwheel;
172 struct callout_tailq cc_expireq;
173 sbintime_t cc_firstevent;
174 sbintime_t cc_lastscan;
175 struct thread *cc_thread;
179 char cc_ktr_event_name[20];
183 #define callout_migrating(c) ((c)->c_iflags & CALLOUT_DFRMIGRATION)
185 #define cc_exec_curr(cc, dir) cc->cc_exec_entity[dir].cc_curr
186 #define cc_exec_last_func(cc, dir) cc->cc_exec_entity[dir].cc_last_func
187 #define cc_exec_last_arg(cc, dir) cc->cc_exec_entity[dir].cc_last_arg
188 #define cc_exec_drain(cc, dir) cc->cc_exec_entity[dir].cc_drain
189 #define cc_exec_next(cc) cc->cc_next
190 #define cc_exec_cancel(cc, dir) cc->cc_exec_entity[dir].cc_cancel
191 #define cc_exec_waiting(cc, dir) cc->cc_exec_entity[dir].cc_waiting
193 #define cc_migration_func(cc, dir) cc->cc_exec_entity[dir].ce_migration_func
194 #define cc_migration_arg(cc, dir) cc->cc_exec_entity[dir].ce_migration_arg
195 #define cc_migration_cpu(cc, dir) cc->cc_exec_entity[dir].ce_migration_cpu
196 #define cc_migration_time(cc, dir) cc->cc_exec_entity[dir].ce_migration_time
197 #define cc_migration_prec(cc, dir) cc->cc_exec_entity[dir].ce_migration_prec
199 static struct callout_cpu cc_cpu[MAXCPU];
200 #define CPUBLOCK MAXCPU
201 #define CC_CPU(cpu) (&cc_cpu[(cpu)])
202 #define CC_SELF() CC_CPU(PCPU_GET(cpuid))
204 static struct callout_cpu cc_cpu;
205 #define CC_CPU(cpu) (&cc_cpu)
206 #define CC_SELF() (&cc_cpu)
208 #define CC_LOCK(cc) mtx_lock_spin(&(cc)->cc_lock)
209 #define CC_UNLOCK(cc) mtx_unlock_spin(&(cc)->cc_lock)
210 #define CC_LOCK_ASSERT(cc) mtx_assert(&(cc)->cc_lock, MA_OWNED)
212 static int __read_mostly cc_default_cpu;
214 static void callout_cpu_init(struct callout_cpu *cc, int cpu);
215 static void softclock_call_cc(struct callout *c, struct callout_cpu *cc,
216 #ifdef CALLOUT_PROFILING
217 int *mpcalls, int *lockcalls, int *gcalls,
221 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
225 * cc_curr - If a callout is in progress, it is cc_curr.
226 * If cc_curr is non-NULL, threads waiting in
227 * callout_drain() will be woken up as soon as the
228 * relevant callout completes.
229 * cc_cancel - Changing to 1 with both callout_lock and cc_lock held
230 * guarantees that the current callout will not run.
231 * The softclock_call_cc() function sets this to 0 before it
232 * drops callout_lock to acquire c_lock, and it calls
233 * the handler only if curr_cancelled is still 0 after
234 * cc_lock is successfully acquired.
235 * cc_waiting - If a thread is waiting in callout_drain(), then
236 * callout_wait is nonzero. Set only when
237 * cc_curr is non-NULL.
241 * Resets the execution entity tied to a specific callout cpu.
244 cc_cce_cleanup(struct callout_cpu *cc, int direct)
247 cc_exec_curr(cc, direct) = NULL;
248 cc_exec_cancel(cc, direct) = false;
249 cc_exec_waiting(cc, direct) = false;
251 cc_migration_cpu(cc, direct) = CPUBLOCK;
252 cc_migration_time(cc, direct) = 0;
253 cc_migration_prec(cc, direct) = 0;
254 cc_migration_func(cc, direct) = NULL;
255 cc_migration_arg(cc, direct) = NULL;
260 * Checks if migration is requested by a specific callout cpu.
263 cc_cce_migrating(struct callout_cpu *cc, int direct)
267 return (cc_migration_cpu(cc, direct) != CPUBLOCK);
274 * Kernel low level callwheel initialization
275 * called on the BSP during kernel startup.
278 callout_callwheel_init(void *dummy)
280 struct callout_cpu *cc;
284 * Calculate the size of the callout wheel and the preallocated
285 * timeout() structures.
286 * XXX: Clip callout to result of previous function of maxusers
287 * maximum 384. This is still huge, but acceptable.
289 ncallout = imin(16 + maxproc + maxfiles, 18508);
290 TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
293 * Calculate callout wheel size, should be next power of two higher
296 callwheelsize = 1 << fls(ncallout);
297 callwheelmask = callwheelsize - 1;
300 * Fetch whether we're pinning the swi's or not.
302 TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
303 TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
306 * Initialize callout wheels. The software interrupt threads
309 cc_default_cpu = PCPU_GET(cpuid);
312 callout_cpu_init(cc, cpu);
315 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
318 * Initialize the per-cpu callout structures.
321 callout_cpu_init(struct callout_cpu *cc, int cpu)
325 mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN);
327 cc->cc_callwheel = malloc_domainset(sizeof(struct callout_list) *
328 callwheelsize, M_CALLOUT,
329 DOMAINSET_PREF(pcpu_find(cpu)->pc_domain), M_WAITOK);
330 for (i = 0; i < callwheelsize; i++)
331 LIST_INIT(&cc->cc_callwheel[i]);
332 TAILQ_INIT(&cc->cc_expireq);
333 cc->cc_firstevent = SBT_MAX;
334 for (i = 0; i < 2; i++)
335 cc_cce_cleanup(cc, i);
337 snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
338 "callwheel cpu %d", cpu);
344 * Switches the cpu tied to a specific callout.
345 * The function expects a locked incoming callout cpu and returns with
346 * locked outcoming callout cpu.
348 static struct callout_cpu *
349 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
351 struct callout_cpu *new_cc;
353 MPASS(c != NULL && cc != NULL);
357 * Avoid interrupts and preemption firing after the callout cpu
358 * is blocked in order to avoid deadlocks as the new thread
359 * may be willing to acquire the callout cpu lock.
364 new_cc = CC_CPU(new_cpu);
373 * Start softclock threads.
376 start_softclock(void *dummy)
380 struct callout_cpu *cc;
387 error = kproc_kthread_add(softclock_thread, cc, &p, &td,
388 RFSTOPPED, 0, "clock", "clock (%d)", cpu);
390 panic("failed to create softclock thread for cpu %d: %d",
395 sched_class(td, PRI_ITHD);
396 sched_prio(td, PI_SOFTCLOCK);
398 thread_lock_set(td, (struct mtx *)&cc->cc_lock);
400 if (cpu == cc_default_cpu)
401 pin_swi = pin_default_swi;
403 pin_swi = pin_pcpu_swi;
405 error = cpuset_setithread(td->td_tid, cpu);
407 printf("%s: %s clock couldn't be pinned to cpu %d: %d\n",
408 __func__, cpu == cc_default_cpu ?
409 "default" : "per-cpu", cpu, error);
413 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
415 #define CC_HASH_SHIFT 8
418 callout_hash(sbintime_t sbt)
421 return (sbt >> (32 - CC_HASH_SHIFT));
425 callout_get_bucket(sbintime_t sbt)
428 return (callout_hash(sbt) & callwheelmask);
432 callout_process(sbintime_t now)
434 struct callout_entropy {
435 struct callout_cpu *cc;
439 struct callout *tmp, *tmpn;
440 struct callout_cpu *cc;
441 struct callout_list *sc;
443 sbintime_t first, last, lookahead, max, tmp_max;
444 u_int firstb, lastb, nowb;
445 #ifdef CALLOUT_PROFILING
446 int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
450 mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
452 /* Compute the buckets of the last scan and present times. */
453 firstb = callout_hash(cc->cc_lastscan);
454 cc->cc_lastscan = now;
455 nowb = callout_hash(now);
457 /* Compute the last bucket and minimum time of the bucket after it. */
459 lookahead = (SBT_1S / 16);
460 else if (nowb - firstb == 1)
461 lookahead = (SBT_1S / 8);
465 first += (lookahead / 2);
467 last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
468 lastb = callout_hash(last) - 1;
472 * Check if we wrapped around the entire wheel from the last scan.
473 * In case, we need to scan entirely the wheel for pending callouts.
475 if (lastb - firstb >= callwheelsize) {
476 lastb = firstb + callwheelsize - 1;
477 if (nowb - firstb >= callwheelsize)
481 /* Iterate callwheel from firstb to nowb and then up to lastb. */
483 sc = &cc->cc_callwheel[firstb & callwheelmask];
484 tmp = LIST_FIRST(sc);
485 while (tmp != NULL) {
486 /* Run the callout if present time within allowed. */
487 if (tmp->c_time <= now) {
489 * Consumer told us the callout may be run
490 * directly from hardware interrupt context.
492 if (tmp->c_iflags & CALLOUT_DIRECT) {
493 #ifdef CALLOUT_PROFILING
497 LIST_NEXT(tmp, c_links.le);
498 cc->cc_bucket = firstb & callwheelmask;
499 LIST_REMOVE(tmp, c_links.le);
500 softclock_call_cc(tmp, cc,
501 #ifdef CALLOUT_PROFILING
502 &mpcalls_dir, &lockcalls_dir, NULL,
505 tmp = cc_exec_next(cc);
506 cc_exec_next(cc) = NULL;
508 tmpn = LIST_NEXT(tmp, c_links.le);
509 LIST_REMOVE(tmp, c_links.le);
510 TAILQ_INSERT_TAIL(&cc->cc_expireq,
512 tmp->c_iflags |= CALLOUT_PROCESSED;
517 /* Skip events from distant future. */
518 if (tmp->c_time >= max)
521 * Event minimal time is bigger than present maximal
522 * time, so it cannot be aggregated.
524 if (tmp->c_time > last) {
528 /* Update first and last time, respecting this event. */
529 if (tmp->c_time < first)
531 tmp_max = tmp->c_time + tmp->c_precision;
535 tmp = LIST_NEXT(tmp, c_links.le);
537 /* Proceed with the next bucket. */
540 * Stop if we looked after present time and found
541 * some event we can't execute at now.
542 * Stop if we looked far enough into the future.
544 } while (((int)(firstb - lastb)) <= 0);
545 cc->cc_firstevent = last;
546 cpu_new_callout(curcpu, last, first);
548 #ifdef CALLOUT_PROFILING
549 avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
550 avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
551 avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
553 if (!TAILQ_EMPTY(&cc->cc_expireq)) {
555 entropy.td = curthread;
557 random_harvest_queue(&entropy, sizeof(entropy), RANDOM_CALLOUT);
560 if (TD_AWAITING_INTR(td)) {
561 thread_lock_block_wait(td);
562 THREAD_LOCK_ASSERT(td, MA_OWNED);
564 sched_add(td, SRQ_INTR);
566 mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
568 mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
571 static struct callout_cpu *
572 callout_lock(struct callout *c)
574 struct callout_cpu *cc;
580 if (cpu == CPUBLOCK) {
581 while (c->c_cpu == CPUBLOCK)
596 callout_cc_add(struct callout *c, struct callout_cpu *cc,
597 sbintime_t sbt, sbintime_t precision, void (*func)(void *),
598 void *arg, int cpu, int flags)
603 if (sbt < cc->cc_lastscan)
604 sbt = cc->cc_lastscan;
606 c->c_iflags |= CALLOUT_PENDING;
607 c->c_iflags &= ~CALLOUT_PROCESSED;
608 c->c_flags |= CALLOUT_ACTIVE;
609 if (flags & C_DIRECT_EXEC)
610 c->c_iflags |= CALLOUT_DIRECT;
613 c->c_precision = precision;
614 bucket = callout_get_bucket(c->c_time);
615 CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
616 c, (int)(c->c_precision >> 32),
617 (u_int)(c->c_precision & 0xffffffff));
618 LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
619 if (cc->cc_bucket == bucket)
620 cc_exec_next(cc) = c;
623 * Inform the eventtimers(4) subsystem there's a new callout
624 * that has been inserted, but only if really required.
626 if (SBT_MAX - c->c_time < c->c_precision)
627 c->c_precision = SBT_MAX - c->c_time;
628 sbt = c->c_time + c->c_precision;
629 if (sbt < cc->cc_firstevent) {
630 cc->cc_firstevent = sbt;
631 cpu_new_callout(cpu, sbt, c->c_time);
636 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
637 #ifdef CALLOUT_PROFILING
638 int *mpcalls, int *lockcalls, int *gcalls,
642 struct rm_priotracker tracker;
643 callout_func_t *c_func, *drain;
645 struct lock_class *class;
646 struct lock_object *c_lock;
647 uintptr_t lock_status;
650 struct callout_cpu *new_cc;
651 callout_func_t *new_func;
654 sbintime_t new_prec, new_time;
656 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
657 sbintime_t sbt1, sbt2;
659 static sbintime_t maxdt = 2 * SBT_1MS; /* 2 msec */
660 static callout_func_t *lastfunc;
663 KASSERT((c->c_iflags & CALLOUT_PENDING) == CALLOUT_PENDING,
664 ("softclock_call_cc: pend %p %x", c, c->c_iflags));
665 KASSERT((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE,
666 ("softclock_call_cc: act %p %x", c, c->c_flags));
667 class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
669 if (c->c_iflags & CALLOUT_SHAREDLOCK) {
670 if (class == &lock_class_rm)
671 lock_status = (uintptr_t)&tracker;
678 c_iflags = c->c_iflags;
679 c->c_iflags &= ~CALLOUT_PENDING;
681 cc_exec_curr(cc, direct) = c;
682 cc_exec_last_func(cc, direct) = c_func;
683 cc_exec_last_arg(cc, direct) = c_arg;
684 cc_exec_cancel(cc, direct) = false;
685 cc_exec_drain(cc, direct) = NULL;
687 if (c_lock != NULL) {
688 class->lc_lock(c_lock, lock_status);
690 * The callout may have been cancelled
691 * while we switched locks.
693 if (cc_exec_cancel(cc, direct)) {
694 class->lc_unlock(c_lock);
697 /* The callout cannot be stopped now. */
698 cc_exec_cancel(cc, direct) = true;
699 if (c_lock == &Giant.lock_object) {
700 #ifdef CALLOUT_PROFILING
703 CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
706 #ifdef CALLOUT_PROFILING
709 CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
713 #ifdef CALLOUT_PROFILING
716 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
719 KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
720 "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
721 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
724 THREAD_NO_SLEEPING();
725 SDT_PROBE1(callout_execute, , , callout__start, c);
727 SDT_PROBE1(callout_execute, , , callout__end, c);
728 THREAD_SLEEPING_OK();
729 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
733 if (lastfunc != c_func || sbt2 > maxdt * 2) {
736 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
737 c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
743 KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
744 CTR1(KTR_CALLOUT, "callout %p finished", c);
745 if ((c_iflags & CALLOUT_RETURNUNLOCKED) == 0)
746 class->lc_unlock(c_lock);
749 KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
750 cc_exec_curr(cc, direct) = NULL;
751 if (cc_exec_drain(cc, direct)) {
752 drain = cc_exec_drain(cc, direct);
753 cc_exec_drain(cc, direct) = NULL;
758 if (cc_exec_waiting(cc, direct)) {
760 * There is someone waiting for the
761 * callout to complete.
762 * If the callout was scheduled for
763 * migration just cancel it.
765 if (cc_cce_migrating(cc, direct)) {
766 cc_cce_cleanup(cc, direct);
769 * It should be assert here that the callout is not
770 * destroyed but that is not easy.
772 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
774 cc_exec_waiting(cc, direct) = false;
776 wakeup(&cc_exec_waiting(cc, direct));
778 } else if (cc_cce_migrating(cc, direct)) {
781 * If the callout was scheduled for
782 * migration just perform it now.
784 new_cpu = cc_migration_cpu(cc, direct);
785 new_time = cc_migration_time(cc, direct);
786 new_prec = cc_migration_prec(cc, direct);
787 new_func = cc_migration_func(cc, direct);
788 new_arg = cc_migration_arg(cc, direct);
789 cc_cce_cleanup(cc, direct);
792 * It should be assert here that the callout is not destroyed
793 * but that is not easy.
795 * As first thing, handle deferred callout stops.
797 if (!callout_migrating(c)) {
799 "deferred cancelled %p func %p arg %p",
800 c, new_func, new_arg);
803 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
805 new_cc = callout_cpu_switch(c, cc, new_cpu);
806 flags = (direct) ? C_DIRECT_EXEC : 0;
807 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
808 new_arg, new_cpu, flags);
812 panic("migration should not happen");
818 * The callout mechanism is based on the work of Adam M. Costello and
819 * George Varghese, published in a technical report entitled "Redesigning
820 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
821 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
822 * used in this implementation was published by G. Varghese and T. Lauck in
823 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
824 * the Efficient Implementation of a Timer Facility" in the Proceedings of
825 * the 11th ACM Annual Symposium on Operating Systems Principles,
826 * Austin, Texas Nov 1987.
830 * Software (low priority) clock interrupt thread handler.
831 * Run periodic events from timeout queue.
834 softclock_thread(void *arg)
836 struct thread *td = curthread;
837 struct callout_cpu *cc;
839 #ifdef CALLOUT_PROFILING
840 int depth, gcalls, lockcalls, mpcalls;
843 cc = (struct callout_cpu *)arg;
846 while (TAILQ_EMPTY(&cc->cc_expireq)) {
848 * Use CC_LOCK(cc) as the thread_lock while
852 thread_lock_set(td, (struct mtx *)&cc->cc_lock);
854 mi_switch(SW_VOL | SWT_IWAIT);
856 /* mi_switch() drops thread_lock(). */
860 #ifdef CALLOUT_PROFILING
861 depth = gcalls = lockcalls = mpcalls = 0;
863 while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
864 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
865 softclock_call_cc(c, cc,
866 #ifdef CALLOUT_PROFILING
867 &mpcalls, &lockcalls, &gcalls,
870 #ifdef CALLOUT_PROFILING
874 #ifdef CALLOUT_PROFILING
875 avg_depth += (depth * 1000 - avg_depth) >> 8;
876 avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
877 avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
878 avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
884 callout_when(sbintime_t sbt, sbintime_t precision, int flags,
885 sbintime_t *res, sbintime_t *prec_res)
887 sbintime_t to_sbt, to_pr;
889 if ((flags & (C_ABSOLUTE | C_PRECALC)) != 0) {
891 *prec_res = precision;
894 if ((flags & C_HARDCLOCK) != 0 && sbt < tick_sbt)
896 if ((flags & C_HARDCLOCK) != 0 || sbt >= sbt_tickthreshold) {
898 * Obtain the time of the last hardclock() call on
899 * this CPU directly from the kern_clocksource.c.
900 * This value is per-CPU, but it is equal for all
904 to_sbt = DPCPU_GET(hardclocktime);
907 to_sbt = DPCPU_GET(hardclocktime);
910 if (cold && to_sbt == 0)
911 to_sbt = sbinuptime();
912 if ((flags & C_HARDCLOCK) == 0)
915 to_sbt = sbinuptime();
916 if (SBT_MAX - to_sbt < sbt)
921 to_pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
922 sbt >> C_PRELGET(flags));
923 *prec_res = to_pr > precision ? to_pr : precision;
927 * New interface; clients allocate their own callout structures.
929 * callout_reset() - establish or change a timeout
930 * callout_stop() - disestablish a timeout
931 * callout_init() - initialize a callout structure so that it can
932 * safely be passed to callout_reset() and callout_stop()
934 * <sys/callout.h> defines three convenience macros:
936 * callout_active() - returns truth if callout has not been stopped,
937 * drained, or deactivated since the last time the callout was
939 * callout_pending() - returns truth if callout is still waiting for timeout
940 * callout_deactivate() - marks the callout as having been serviced
943 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t prec,
944 callout_func_t *ftn, void *arg, int cpu, int flags)
946 sbintime_t to_sbt, precision;
947 struct callout_cpu *cc;
948 int cancelled, direct;
954 } else if ((cpu >= MAXCPU) ||
955 ((CC_CPU(cpu))->cc_inited == 0)) {
956 /* Invalid CPU spec */
957 panic("Invalid CPU in callout %d", cpu);
959 callout_when(sbt, prec, flags, &to_sbt, &precision);
962 * This flag used to be added by callout_cc_add, but the
963 * first time you call this we could end up with the
964 * wrong direct flag if we don't do it before we add.
966 if (flags & C_DIRECT_EXEC) {
971 KASSERT(!direct || c->c_lock == NULL ||
972 (LOCK_CLASS(c->c_lock)->lc_flags & LC_SPINLOCK),
973 ("%s: direct callout %p has non-spin lock", __func__, c));
974 cc = callout_lock(c);
976 * Don't allow migration if the user does not care.
982 if (cc_exec_curr(cc, direct) == c) {
984 * We're being asked to reschedule a callout which is
985 * currently in progress. If there is a lock then we
986 * can cancel the callout if it has not really started.
988 if (c->c_lock != NULL && !cc_exec_cancel(cc, direct))
989 cancelled = cc_exec_cancel(cc, direct) = true;
990 if (cc_exec_waiting(cc, direct) || cc_exec_drain(cc, direct)) {
992 * Someone has called callout_drain to kill this
993 * callout. Don't reschedule.
995 CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
996 cancelled ? "cancelled" : "failed to cancel",
997 c, c->c_func, c->c_arg);
1002 if (callout_migrating(c)) {
1004 * This only occurs when a second callout_reset_sbt_on
1005 * is made after a previous one moved it into
1006 * deferred migration (below). Note we do *not* change
1007 * the prev_cpu even though the previous target may
1010 cc_migration_cpu(cc, direct) = cpu;
1011 cc_migration_time(cc, direct) = to_sbt;
1012 cc_migration_prec(cc, direct) = precision;
1013 cc_migration_func(cc, direct) = ftn;
1014 cc_migration_arg(cc, direct) = arg;
1021 if (c->c_iflags & CALLOUT_PENDING) {
1022 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
1023 if (cc_exec_next(cc) == c)
1024 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
1025 LIST_REMOVE(c, c_links.le);
1027 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
1030 c->c_iflags &= ~ CALLOUT_PENDING;
1031 c->c_flags &= ~ CALLOUT_ACTIVE;
1036 * If the callout must migrate try to perform it immediately.
1037 * If the callout is currently running, just defer the migration
1038 * to a more appropriate moment.
1040 if (c->c_cpu != cpu) {
1041 if (cc_exec_curr(cc, direct) == c) {
1043 * Pending will have been removed since we are
1044 * actually executing the callout on another
1045 * CPU. That callout should be waiting on the
1046 * lock the caller holds. If we set both
1047 * active/and/pending after we return and the
1048 * lock on the executing callout proceeds, it
1049 * will then see pending is true and return.
1050 * At the return from the actual callout execution
1051 * the migration will occur in softclock_call_cc
1052 * and this new callout will be placed on the
1053 * new CPU via a call to callout_cpu_switch() which
1054 * will get the lock on the right CPU followed
1055 * by a call callout_cc_add() which will add it there.
1056 * (see above in softclock_call_cc()).
1058 cc_migration_cpu(cc, direct) = cpu;
1059 cc_migration_time(cc, direct) = to_sbt;
1060 cc_migration_prec(cc, direct) = precision;
1061 cc_migration_func(cc, direct) = ftn;
1062 cc_migration_arg(cc, direct) = arg;
1063 c->c_iflags |= (CALLOUT_DFRMIGRATION | CALLOUT_PENDING);
1064 c->c_flags |= CALLOUT_ACTIVE;
1066 "migration of %p func %p arg %p in %d.%08x to %u deferred",
1067 c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
1068 (u_int)(to_sbt & 0xffffffff), cpu);
1072 cc = callout_cpu_switch(c, cc, cpu);
1076 callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
1077 CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
1078 cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
1079 (u_int)(to_sbt & 0xffffffff));
1086 * Common idioms that can be optimized in the future.
1089 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
1091 return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
1095 callout_schedule(struct callout *c, int to_ticks)
1097 return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
1101 _callout_stop_safe(struct callout *c, int flags, callout_func_t *drain)
1103 struct callout_cpu *cc, *old_cc;
1104 struct lock_class *class;
1105 int direct, sq_locked, use_lock;
1106 int cancelled, not_on_a_list;
1108 if ((flags & CS_DRAIN) != 0)
1109 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
1110 "calling %s", __func__);
1112 KASSERT((flags & CS_DRAIN) == 0 || drain == NULL,
1113 ("Cannot set drain callback and CS_DRAIN flag at the same time"));
1116 * Some old subsystems don't hold Giant while running a callout_stop(),
1117 * so just discard this check for the moment.
1119 if ((flags & CS_DRAIN) == 0 && c->c_lock != NULL) {
1120 if (c->c_lock == &Giant.lock_object)
1121 use_lock = mtx_owned(&Giant);
1124 class = LOCK_CLASS(c->c_lock);
1125 class->lc_assert(c->c_lock, LA_XLOCKED);
1129 if (c->c_iflags & CALLOUT_DIRECT) {
1137 cc = callout_lock(c);
1139 if ((c->c_iflags & (CALLOUT_DFRMIGRATION | CALLOUT_PENDING)) ==
1140 (CALLOUT_DFRMIGRATION | CALLOUT_PENDING) &&
1141 ((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE)) {
1143 * Special case where this slipped in while we
1144 * were migrating *as* the callout is about to
1145 * execute. The caller probably holds the lock
1146 * the callout wants.
1148 * Get rid of the migration first. Then set
1149 * the flag that tells this code *not* to
1150 * try to remove it from any lists (its not
1151 * on one yet). When the callout wheel runs,
1152 * it will ignore this callout.
1154 c->c_iflags &= ~CALLOUT_PENDING;
1155 c->c_flags &= ~CALLOUT_ACTIVE;
1162 * If the callout was migrating while the callout cpu lock was
1163 * dropped, just drop the sleepqueue lock and check the states
1166 if (sq_locked != 0 && cc != old_cc) {
1169 sleepq_release(&cc_exec_waiting(old_cc, direct));
1174 panic("migration should not happen");
1179 * If the callout is running, try to stop it or drain it.
1181 if (cc_exec_curr(cc, direct) == c) {
1183 * Succeed we to stop it or not, we must clear the
1184 * active flag - this is what API users expect. If we're
1185 * draining and the callout is currently executing, first wait
1186 * until it finishes.
1188 if ((flags & CS_DRAIN) == 0)
1189 c->c_flags &= ~CALLOUT_ACTIVE;
1191 if ((flags & CS_DRAIN) != 0) {
1193 * The current callout is running (or just
1194 * about to run) and blocking is allowed, so
1195 * just wait for the current invocation to
1198 if (cc_exec_curr(cc, direct) == c) {
1200 * Use direct calls to sleepqueue interface
1201 * instead of cv/msleep in order to avoid
1202 * a LOR between cc_lock and sleepqueue
1203 * chain spinlocks. This piece of code
1204 * emulates a msleep_spin() call actually.
1206 * If we already have the sleepqueue chain
1207 * locked, then we can safely block. If we
1208 * don't already have it locked, however,
1209 * we have to drop the cc_lock to lock
1210 * it. This opens several races, so we
1211 * restart at the beginning once we have
1212 * both locks. If nothing has changed, then
1213 * we will end up back here with sq_locked
1219 &cc_exec_waiting(cc, direct));
1226 * Migration could be cancelled here, but
1227 * as long as it is still not sure when it
1228 * will be packed up, just let softclock()
1231 cc_exec_waiting(cc, direct) = true;
1235 &cc_exec_waiting(cc, direct),
1236 &cc->cc_lock.lock_object, "codrain",
1239 &cc_exec_waiting(cc, direct),
1244 /* Reacquire locks previously released. */
1248 c->c_flags &= ~CALLOUT_ACTIVE;
1249 } else if (use_lock &&
1250 !cc_exec_cancel(cc, direct) && (drain == NULL)) {
1253 * The current callout is waiting for its
1254 * lock which we hold. Cancel the callout
1255 * and return. After our caller drops the
1256 * lock, the callout will be skipped in
1257 * softclock(). This *only* works with a
1258 * callout_stop() *not* callout_drain() or
1259 * callout_async_drain().
1261 cc_exec_cancel(cc, direct) = true;
1262 CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
1263 c, c->c_func, c->c_arg);
1264 KASSERT(!cc_cce_migrating(cc, direct),
1265 ("callout wrongly scheduled for migration"));
1266 if (callout_migrating(c)) {
1267 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
1269 cc_migration_cpu(cc, direct) = CPUBLOCK;
1270 cc_migration_time(cc, direct) = 0;
1271 cc_migration_prec(cc, direct) = 0;
1272 cc_migration_func(cc, direct) = NULL;
1273 cc_migration_arg(cc, direct) = NULL;
1277 KASSERT(!sq_locked, ("sleepqueue chain locked"));
1279 } else if (callout_migrating(c)) {
1281 * The callout is currently being serviced
1282 * and the "next" callout is scheduled at
1283 * its completion with a migration. We remove
1284 * the migration flag so it *won't* get rescheduled,
1285 * but we can't stop the one thats running so
1288 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
1291 * We can't call cc_cce_cleanup here since
1292 * if we do it will remove .ce_curr and
1293 * its still running. This will prevent a
1294 * reschedule of the callout when the
1295 * execution completes.
1297 cc_migration_cpu(cc, direct) = CPUBLOCK;
1298 cc_migration_time(cc, direct) = 0;
1299 cc_migration_prec(cc, direct) = 0;
1300 cc_migration_func(cc, direct) = NULL;
1301 cc_migration_arg(cc, direct) = NULL;
1303 CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
1304 c, c->c_func, c->c_arg);
1306 KASSERT(cc_exec_drain(cc, direct) == NULL,
1307 ("callout drain function already set to %p",
1308 cc_exec_drain(cc, direct)));
1309 cc_exec_drain(cc, direct) = drain;
1314 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
1315 c, c->c_func, c->c_arg);
1317 KASSERT(cc_exec_drain(cc, direct) == NULL,
1318 ("callout drain function already set to %p",
1319 cc_exec_drain(cc, direct)));
1320 cc_exec_drain(cc, direct) = drain;
1323 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
1329 sleepq_release(&cc_exec_waiting(cc, direct));
1331 if ((c->c_iflags & CALLOUT_PENDING) == 0) {
1332 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
1333 c, c->c_func, c->c_arg);
1335 * For not scheduled and not executing callout return
1338 if (cc_exec_curr(cc, direct) != c)
1344 c->c_iflags &= ~CALLOUT_PENDING;
1345 c->c_flags &= ~CALLOUT_ACTIVE;
1347 CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
1348 c, c->c_func, c->c_arg);
1349 if (not_on_a_list == 0) {
1350 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
1351 if (cc_exec_next(cc) == c)
1352 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
1353 LIST_REMOVE(c, c_links.le);
1355 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
1363 callout_init(struct callout *c, int mpsafe)
1365 bzero(c, sizeof *c);
1368 c->c_iflags = CALLOUT_RETURNUNLOCKED;
1370 c->c_lock = &Giant.lock_object;
1373 c->c_cpu = cc_default_cpu;
1377 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
1379 bzero(c, sizeof *c);
1381 KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
1382 ("callout_init_lock: bad flags %d", flags));
1383 KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
1384 ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
1385 KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags & LC_SLEEPABLE),
1386 ("%s: callout %p has sleepable lock", __func__, c));
1387 c->c_iflags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
1388 c->c_cpu = cc_default_cpu;
1392 flssbt(sbintime_t sbt)
1395 sbt += (uint64_t)sbt >> 1;
1396 if (sizeof(long) >= sizeof(sbintime_t))
1399 return (flsl(((uint64_t)sbt) >> 32) + 32);
1404 * Dump immediate statistic snapshot of the scheduled callouts.
1407 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
1409 struct callout *tmp;
1410 struct callout_cpu *cc;
1411 struct callout_list *sc;
1412 sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
1413 int ct[64], cpr[64], ccpbk[32];
1414 int error, val, i, count, tcum, pcum, maxc, c, medc;
1418 error = sysctl_handle_int(oidp, &val, 0, req);
1419 if (error != 0 || req->newptr == NULL)
1422 st = spr = maxt = maxpr = 0;
1423 bzero(ccpbk, sizeof(ccpbk));
1424 bzero(ct, sizeof(ct));
1425 bzero(cpr, sizeof(cpr));
1430 for (i = 0; i < callwheelsize; i++) {
1431 sc = &cc->cc_callwheel[i];
1433 LIST_FOREACH(tmp, sc, c_links.le) {
1435 t = tmp->c_time - now;
1439 spr += tmp->c_precision / SBT_1US;
1442 if (tmp->c_precision > maxpr)
1443 maxpr = tmp->c_precision;
1445 cpr[flssbt(tmp->c_precision)]++;
1449 ccpbk[fls(c + c / 2)]++;
1455 for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
1457 medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
1458 for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
1460 medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
1461 for (i = 0, c = 0; i < 32 && c < count / 2; i++)
1463 medc = (i >= 2) ? (1 << (i - 2)) : 0;
1465 printf("Scheduled callouts statistic snapshot:\n");
1466 printf(" Callouts: %6d Buckets: %6d*%-3d Bucket size: 0.%06ds\n",
1467 count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
1468 printf(" C/Bk: med %5d avg %6d.%06jd max %6d\n",
1470 count / callwheelsize / mp_ncpus,
1471 (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
1473 printf(" Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
1474 medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
1475 (st / count) / 1000000, (st / count) % 1000000,
1476 maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
1477 printf(" Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
1478 medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
1479 (spr / count) / 1000000, (spr / count) % 1000000,
1480 maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
1481 printf(" Distribution: \tbuckets\t time\t tcum\t"
1483 for (i = 0, tcum = pcum = 0; i < 64; i++) {
1484 if (ct[i] == 0 && cpr[i] == 0)
1486 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
1489 printf(" %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
1490 t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
1491 i - 1 - (32 - CC_HASH_SHIFT),
1492 ct[i], tcum, cpr[i], pcum);
1496 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
1497 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
1498 0, 0, sysctl_kern_callout_stat, "I",
1499 "Dump immediate statistic snapshot of the scheduled callouts");
1503 _show_callout(struct callout *c)
1506 db_printf("callout %p\n", c);
1507 #define C_DB_PRINTF(f, e) db_printf(" %s = " f "\n", #e, c->e);
1508 db_printf(" &c_links = %p\n", &(c->c_links));
1509 C_DB_PRINTF("%" PRId64, c_time);
1510 C_DB_PRINTF("%" PRId64, c_precision);
1511 C_DB_PRINTF("%p", c_arg);
1512 C_DB_PRINTF("%p", c_func);
1513 C_DB_PRINTF("%p", c_lock);
1514 C_DB_PRINTF("%#x", c_flags);
1515 C_DB_PRINTF("%#x", c_iflags);
1516 C_DB_PRINTF("%d", c_cpu);
1520 DB_SHOW_COMMAND(callout, db_show_callout)
1524 db_printf("usage: show callout <struct callout *>\n");
1528 _show_callout((struct callout *)addr);
1532 _show_last_callout(int cpu, int direct, const char *dirstr)
1534 struct callout_cpu *cc;
1538 func = cc_exec_last_func(cc, direct);
1539 arg = cc_exec_last_arg(cc, direct);
1540 db_printf("cpu %d last%s callout function: %p ", cpu, dirstr, func);
1541 db_printsym((db_expr_t)func, DB_STGY_ANY);
1542 db_printf("\ncpu %d last%s callout argument: %p\n", cpu, dirstr, arg);
1545 DB_SHOW_COMMAND(callout_last, db_show_callout_last)
1550 if (addr < 0 || addr > mp_maxid || CPU_ABSENT(addr)) {
1551 db_printf("no such cpu: %d\n", (int)addr);
1560 while (cpu <= last) {
1561 if (!CPU_ABSENT(cpu)) {
1562 _show_last_callout(cpu, 0, "");
1563 _show_last_callout(cpu, 1, " direct");