2 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
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71 * From: @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
72 * $FreeBSD: src/sys/kern/kern_timeout.c,v 1.59.2.1 2001/11/13 18:24:52 archie Exp $
73 * $DragonFly: src/sys/kern/kern_timeout.c,v 1.27 2007/11/14 18:27:52 swildner Exp $
76 * DRAGONFLY BGL STATUS
78 * All the API functions should be MP safe.
80 * The callback functions will be flagged as being MP safe if the
81 * timeout structure is initialized with callout_init_mp() instead of
84 * The helper threads cannot be made preempt-capable until after we
85 * clean up all the uses of splsoftclock() and related interlocks (which
86 * require the related functions to be MP safe as well).
89 * The callout mechanism is based on the work of Adam M. Costello and
90 * George Varghese, published in a technical report entitled "Redesigning
91 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
92 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
93 * used in this implementation was published by G. Varghese and T. Lauck in
94 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
95 * the Efficient Implementation of a Timer Facility" in the Proceedings of
96 * the 11th ACM Annual Symposium on Operating Systems Principles,
97 * Austin, Texas Nov 1987.
99 * The per-cpu augmentation was done by Matthew Dillon.
102 #include <sys/param.h>
103 #include <sys/systm.h>
104 #include <sys/callout.h>
105 #include <sys/kernel.h>
106 #include <sys/interrupt.h>
107 #include <sys/thread.h>
109 #include <sys/thread2.h>
110 #include <sys/mplock2.h>
112 #ifndef MAX_SOFTCLOCK_STEPS
113 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
117 struct softclock_pcpu {
118 struct callout_tailq *callwheel;
119 struct callout * volatile next;
120 struct callout *running;/* currently running callout */
121 int softticks; /* softticks index */
122 int curticks; /* per-cpu ticks counter */
124 struct thread thread;
128 typedef struct softclock_pcpu *softclock_pcpu_t;
132 * allocate more timeout table slots when table overflows.
134 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures");
135 static int callwheelsize;
136 static int callwheelbits;
137 static int callwheelmask;
138 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU];
140 static void softclock_handler(void *arg);
143 swi_softclock_setup(void *arg)
149 * Figure out how large a callwheel we need. It must be a power of 2.
153 while (callwheelsize < ncallout) {
157 callwheelmask = callwheelsize - 1;
160 * Initialize per-cpu data structures.
162 for (cpu = 0; cpu < ncpus; ++cpu) {
165 sc = &softclock_pcpu_ary[cpu];
167 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize,
168 M_CALLOUT, M_WAITOK|M_ZERO);
169 for (i = 0; i < callwheelsize; ++i)
170 TAILQ_INIT(&sc->callwheel[i]);
173 * Mark the softclock handler as being an interrupt thread
174 * even though it really isn't, but do not allow it to
175 * preempt other threads (do not assign td_preemptable).
177 * Kernel code now assumes that callouts do not preempt
178 * the cpu they were scheduled on.
180 lwkt_create(softclock_handler, sc, NULL,
181 &sc->thread, TDF_NOSTART | TDF_INTTHREAD,
182 cpu, "softclock %d", cpu);
187 * Must occur after ncpus has been initialized.
189 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND,
190 swi_softclock_setup, NULL);
193 * This routine is called from the hardclock() (basically a FASTint/IPI) on
194 * each cpu in the system. sc->curticks is this cpu's notion of the timebase.
195 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where
196 * the callwheel is currently indexed.
198 * WARNING! The MP lock is not necessarily held on call, nor can it be
201 * sc->softticks is adjusted by either this routine or our helper thread
202 * depending on whether the helper thread is running or not.
205 hardclock_softtick(globaldata_t gd)
209 sc = &softclock_pcpu_ary[gd->gd_cpuid];
213 if (sc->softticks == sc->curticks) {
215 * in sync, only wakeup the thread if there is something to
218 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask]))
221 lwkt_schedule(&sc->thread);
227 * out of sync, wakeup the thread unconditionally so it can
231 lwkt_schedule(&sc->thread);
236 * This procedure is the main loop of our per-cpu helper thread. The
237 * sc->isrunning flag prevents us from racing hardclock_softtick() and
238 * a critical section is sufficient to interlock sc->curticks and protect
239 * us from remote IPI's / list removal.
241 * The thread starts with the MP lock released and not in a critical
242 * section. The loop itself is MP safe while individual callbacks
243 * may or may not be, so we obtain or release the MP lock as appropriate.
246 softclock_handler(void *arg)
250 struct callout_tailq *bucket;
251 void (*c_func)(void *);
258 * Run the callout thread at the same priority as other kernel
259 * threads so it can be round-robined.
261 /*lwkt_setpri_self(TDPRI_SOFT_NORM);*/
266 while (sc->softticks != (int)(sc->curticks + 1)) {
267 bucket = &sc->callwheel[sc->softticks & callwheelmask];
269 for (c = TAILQ_FIRST(bucket); c; c = sc->next) {
270 if (c->c_time != sc->softticks) {
271 sc->next = TAILQ_NEXT(c, c_links.tqe);
275 if (c->c_flags & CALLOUT_MPSAFE) {
282 * The request might be removed while we
283 * are waiting to get the MP lock. If it
284 * was removed sc->next will point to the
285 * next valid request or NULL, loop up.
296 sc->next = TAILQ_NEXT(c, c_links.tqe);
297 TAILQ_REMOVE(bucket, c, c_links.tqe);
303 KKASSERT(c->c_flags & CALLOUT_DID_INIT);
304 c->c_flags &= ~CALLOUT_PENDING;
309 /* NOTE: list may have changed */
314 lwkt_deschedule_self(&sc->thread); /* == curthread */
321 * New interface; clients allocate their own callout structures.
323 * callout_reset() - establish or change a timeout
324 * callout_stop() - disestablish a timeout
325 * callout_init() - initialize a callout structure so that it can
326 * safely be passed to callout_reset() and callout_stop()
327 * callout_init_mp() - same but any installed functions must be MP safe.
329 * <sys/callout.h> defines three convenience macros:
331 * callout_active() - returns truth if callout has not been serviced
332 * callout_pending() - returns truth if callout is still waiting for timeout
333 * callout_deactivate() - marks the callout as having been serviced
337 * Start or restart a timeout. Install the callout structure in the
338 * callwheel. Callers may legally pass any value, even if 0 or negative,
339 * but since the sc->curticks index may have already been processed a
340 * minimum timeout of 1 tick will be enforced.
342 * The callout is installed on and will be processed on the current cpu's
345 * WARNING! This function may be called from any cpu but the caller must
346 * serialize callout_stop() and callout_reset() calls on the passed
347 * structure regardless of cpu.
350 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
357 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
360 "callout_reset(%p) from %p: callout was not initialized\n",
361 c, ((int **)&c)[-1]);
366 sc = &softclock_pcpu_ary[gd->gd_cpuid];
369 if (c->c_flags & CALLOUT_ACTIVE)
376 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
378 c->c_time = sc->curticks + to_ticks;
383 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask],
389 * Stop a running timer. WARNING! If called on a cpu other then the one
390 * the callout was started on this function will liveloop on its IPI to
391 * the target cpu to process the request. It is possible for the callout
392 * to execute in that case.
394 * WARNING! This function may be called from any cpu but the caller must
395 * serialize callout_stop() and callout_reset() calls on the passed
396 * structure regardless of cpu.
398 * WARNING! This routine may be called from an IPI
400 * WARNING! This function can return while it's c_func is still running
401 * in the callout thread, a secondary check may be needed.
402 * Use callout_stop_sync() to wait for any callout function to
403 * complete before returning, being sure that no deadlock is
404 * possible if you do.
407 callout_stop(struct callout *c)
409 globaldata_t gd = mycpu;
416 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
419 "callout_stop(%p) from %p: callout was not initialized\n",
420 c, ((int **)&c)[-1]);
427 * Don't attempt to delete a callout that's not on the queue. The
428 * callout may not have a cpu assigned to it. Callers do not have
429 * to be on the issuing cpu but must still serialize access to the
432 * We are not cpu-localized here and cannot safely modify the
433 * flags field in the callout structure. Note that most of the
434 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
436 * If we race another cpu's dispatch of this callout it is possible
437 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
438 * will cause us to fall through and synchronize with the other
441 if ((c->c_flags & CALLOUT_PENDING) == 0) {
443 if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
447 if (c->c_gd == NULL || c->c_gd == gd) {
448 c->c_flags &= ~CALLOUT_ACTIVE;
452 /* fall-through to the cpu-localization code. */
454 c->c_flags &= ~CALLOUT_ACTIVE;
460 if ((tgd = c->c_gd) != gd) {
462 * If the callout is owned by a different CPU we have to
463 * execute the function synchronously on the target cpu.
467 cpu_ccfence(); /* don't let tgd alias c_gd */
468 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
469 lwkt_wait_ipiq(tgd, seq);
474 * If the callout is owned by the same CPU we can
475 * process it directly, but if we are racing our helper
476 * thread (sc->next), we have to adjust sc->next. The
477 * race is interlocked by a critical section.
479 sc = &softclock_pcpu_ary[gd->gd_cpuid];
481 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
483 sc->next = TAILQ_NEXT(c, c_links.tqe);
485 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
494 * Issue a callout_stop() and ensure that any callout race completes
495 * before returning. Does NOT de-initialized the callout.
498 callout_stop_sync(struct callout *c)
502 if (c->c_flags & CALLOUT_DID_INIT) {
506 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
507 if (sc->running == c) {
508 while (sc->running == c)
509 tsleep(&sc->running, 0, "crace", 1);
513 sc = &softclock_pcpu_ary[0];
514 if (sc->running == c) {
515 while (sc->running == c)
516 tsleep(&sc->running, 0, "crace", 1);
519 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
524 * Terminate a callout
526 * This function will stop any pending callout and also block while the
527 * callout's function is running. It should only be used in cases where
528 * no deadlock is possible (due to the callout function acquiring locks
529 * that the current caller of callout_terminate() already holds), when
530 * the caller is ready to destroy the callout structure.
532 * This function clears the CALLOUT_DID_INIT flag.
534 * lwkt_token locks are ok.
537 callout_terminate(struct callout *c)
541 if (c->c_flags & CALLOUT_DID_INIT) {
544 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
546 sc = &softclock_pcpu_ary[0];
548 if (sc->running == c) {
549 while (sc->running == c)
550 tsleep(&sc->running, 0, "crace", 1);
552 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
553 c->c_flags &= ~CALLOUT_DID_INIT;
558 * Prepare a callout structure for use by callout_reset() and/or
559 * callout_stop(). The MP version of this routine requires that the callback
560 * function installed by callout_reset() be MP safe.
562 * The init functions can be called from any cpu and do not have to be
563 * called from the cpu that the timer will eventually run on.
566 callout_init(struct callout *c)
569 c->c_flags = CALLOUT_DID_INIT;
573 callout_init_mp(struct callout *c)
576 c->c_flags |= CALLOUT_MPSAFE;
579 /* What, are you joking? This is nuts! -Matt */
581 #ifdef APM_FIXUP_CALLTODO
583 * Adjust the kernel calltodo timeout list. This routine is used after
584 * an APM resume to recalculate the calltodo timer list values with the
585 * number of hz's we have been sleeping. The next hardclock() will detect
586 * that there are fired timers and run softclock() to execute them.
588 * Please note, I have not done an exhaustive analysis of what code this
589 * might break. I am motivated to have my select()'s and alarm()'s that
590 * have expired during suspend firing upon resume so that the applications
591 * which set the timer can do the maintanence the timer was for as close
592 * as possible to the originally intended time. Testing this code for a
593 * week showed that resuming from a suspend resulted in 22 to 25 timers
594 * firing, which seemed independant on whether the suspend was 2 hours or
595 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
598 adjust_timeout_calltodo(struct timeval *time_change)
601 unsigned long delta_ticks;
604 * How many ticks were we asleep?
605 * (stolen from tvtohz()).
608 /* Don't do anything */
609 if (time_change->tv_sec < 0)
611 else if (time_change->tv_sec <= LONG_MAX / 1000000)
612 delta_ticks = (time_change->tv_sec * 1000000 +
613 time_change->tv_usec + (tick - 1)) / tick + 1;
614 else if (time_change->tv_sec <= LONG_MAX / hz)
615 delta_ticks = time_change->tv_sec * hz +
616 (time_change->tv_usec + (tick - 1)) / tick + 1;
618 delta_ticks = LONG_MAX;
620 if (delta_ticks > INT_MAX)
621 delta_ticks = INT_MAX;
624 * Now rip through the timer calltodo list looking for timers
628 /* don't collide with softclock() */
630 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
631 p->c_time -= delta_ticks;
633 /* Break if the timer had more time on it than delta_ticks */
637 /* take back the ticks the timer didn't use (p->c_time <= 0) */
638 delta_ticks = -p->c_time;
644 #endif /* APM_FIXUP_CALLTODO */