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 $
75 * DRAGONFLY BGL STATUS
77 * All the API functions should be MP safe.
79 * The callback functions will be flagged as being MP safe if the
80 * timeout structure is initialized with callout_init_mp() instead of
83 * The helper threads cannot be made preempt-capable until after we
84 * clean up all the uses of splsoftclock() and related interlocks (which
85 * require the related functions to be MP safe as well).
88 * The callout mechanism is based on the work of Adam M. Costello and
89 * George Varghese, published in a technical report entitled "Redesigning
90 * the BSD Callout and Timer Facilities" and modified slightly for inclusion
91 * in FreeBSD by Justin T. Gibbs. The original work on the data structures
92 * used in this implementation was published by G. Varghese and T. Lauck in
93 * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
94 * the Efficient Implementation of a Timer Facility" in the Proceedings of
95 * the 11th ACM Annual Symposium on Operating Systems Principles,
96 * Austin, Texas Nov 1987.
98 * The per-cpu augmentation was done by Matthew Dillon.
101 #include <sys/param.h>
102 #include <sys/systm.h>
103 #include <sys/callout.h>
104 #include <sys/kernel.h>
105 #include <sys/interrupt.h>
106 #include <sys/thread.h>
108 #include <sys/thread2.h>
109 #include <sys/mplock2.h>
111 #ifndef MAX_SOFTCLOCK_STEPS
112 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
116 struct softclock_pcpu {
117 struct callout_tailq *callwheel;
118 struct callout * volatile next;
119 struct callout *running;/* currently running callout */
120 int softticks; /* softticks index */
121 int curticks; /* per-cpu ticks counter */
123 struct thread thread;
127 typedef struct softclock_pcpu *softclock_pcpu_t;
131 * allocate more timeout table slots when table overflows.
133 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures");
134 static int callwheelsize;
135 static int callwheelmask;
136 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU];
138 static void softclock_handler(void *arg);
141 swi_softclock_setup(void *arg)
147 * Figure out how large a callwheel we need. It must be a power of 2.
150 while (callwheelsize < ncallout)
152 callwheelmask = callwheelsize - 1;
155 * Initialize per-cpu data structures.
157 for (cpu = 0; cpu < ncpus; ++cpu) {
160 sc = &softclock_pcpu_ary[cpu];
162 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize,
163 M_CALLOUT, M_WAITOK|M_ZERO);
164 for (i = 0; i < callwheelsize; ++i)
165 TAILQ_INIT(&sc->callwheel[i]);
168 * Mark the softclock handler as being an interrupt thread
169 * even though it really isn't, but do not allow it to
170 * preempt other threads (do not assign td_preemptable).
172 * Kernel code now assumes that callouts do not preempt
173 * the cpu they were scheduled on.
175 lwkt_create(softclock_handler, sc, NULL,
176 &sc->thread, TDF_NOSTART | TDF_INTTHREAD,
177 cpu, "softclock %d", cpu);
182 * Must occur after ncpus has been initialized.
184 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND,
185 swi_softclock_setup, NULL);
188 * This routine is called from the hardclock() (basically a FASTint/IPI) on
189 * each cpu in the system. sc->curticks is this cpu's notion of the timebase.
190 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where
191 * the callwheel is currently indexed.
193 * WARNING! The MP lock is not necessarily held on call, nor can it be
196 * sc->softticks is adjusted by either this routine or our helper thread
197 * depending on whether the helper thread is running or not.
200 hardclock_softtick(globaldata_t gd)
204 sc = &softclock_pcpu_ary[gd->gd_cpuid];
208 if (sc->softticks == sc->curticks) {
210 * in sync, only wakeup the thread if there is something to
213 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask]))
216 lwkt_schedule(&sc->thread);
222 * out of sync, wakeup the thread unconditionally so it can
226 lwkt_schedule(&sc->thread);
231 * This procedure is the main loop of our per-cpu helper thread. The
232 * sc->isrunning flag prevents us from racing hardclock_softtick() and
233 * a critical section is sufficient to interlock sc->curticks and protect
234 * us from remote IPI's / list removal.
236 * The thread starts with the MP lock released and not in a critical
237 * section. The loop itself is MP safe while individual callbacks
238 * may or may not be, so we obtain or release the MP lock as appropriate.
241 softclock_handler(void *arg)
245 struct callout_tailq *bucket;
246 void (*c_func)(void *);
253 * Run the callout thread at the same priority as other kernel
254 * threads so it can be round-robined.
256 /*lwkt_setpri_self(TDPRI_SOFT_NORM);*/
261 while (sc->softticks != (int)(sc->curticks + 1)) {
262 bucket = &sc->callwheel[sc->softticks & callwheelmask];
264 for (c = TAILQ_FIRST(bucket); c; c = sc->next) {
265 if (c->c_time != sc->softticks) {
266 sc->next = TAILQ_NEXT(c, c_links.tqe);
270 if (c->c_flags & CALLOUT_MPSAFE) {
277 * The request might be removed while we
278 * are waiting to get the MP lock. If it
279 * was removed sc->next will point to the
280 * next valid request or NULL, loop up.
291 sc->next = TAILQ_NEXT(c, c_links.tqe);
292 TAILQ_REMOVE(bucket, c, c_links.tqe);
298 KKASSERT(c->c_flags & CALLOUT_DID_INIT);
299 c->c_flags &= ~CALLOUT_PENDING;
304 /* NOTE: list may have changed */
309 lwkt_deschedule_self(&sc->thread); /* == curthread */
316 * New interface; clients allocate their own callout structures.
318 * callout_reset() - establish or change a timeout
319 * callout_stop() - disestablish a timeout
320 * callout_init() - initialize a callout structure so that it can
321 * safely be passed to callout_reset() and callout_stop()
322 * callout_init_mp() - same but any installed functions must be MP safe.
324 * <sys/callout.h> defines three convenience macros:
326 * callout_active() - returns truth if callout has not been serviced
327 * callout_pending() - returns truth if callout is still waiting for timeout
328 * callout_deactivate() - marks the callout as having been serviced
332 * Start or restart a timeout. Install the callout structure in the
333 * callwheel. Callers may legally pass any value, even if 0 or negative,
334 * but since the sc->curticks index may have already been processed a
335 * minimum timeout of 1 tick will be enforced.
337 * The callout is installed on and will be processed on the current cpu's
340 * WARNING! This function may be called from any cpu but the caller must
341 * serialize callout_stop() and callout_reset() calls on the passed
342 * structure regardless of cpu.
345 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
352 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
355 "callout_reset(%p) from %p: callout was not initialized\n",
356 c, ((int **)&c)[-1]);
361 sc = &softclock_pcpu_ary[gd->gd_cpuid];
364 if (c->c_flags & CALLOUT_ACTIVE)
371 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
373 c->c_time = sc->curticks + to_ticks;
378 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask],
384 * Stop a running timer. WARNING! If called on a cpu other then the one
385 * the callout was started on this function will liveloop on its IPI to
386 * the target cpu to process the request. It is possible for the callout
387 * to execute in that case.
389 * WARNING! This function may be called from any cpu but the caller must
390 * serialize callout_stop() and callout_reset() calls on the passed
391 * structure regardless of cpu.
393 * WARNING! This routine may be called from an IPI
395 * WARNING! This function can return while it's c_func is still running
396 * in the callout thread, a secondary check may be needed.
397 * Use callout_stop_sync() to wait for any callout function to
398 * complete before returning, being sure that no deadlock is
399 * possible if you do.
402 callout_stop(struct callout *c)
404 globaldata_t gd = mycpu;
411 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
414 "callout_stop(%p) from %p: callout was not initialized\n",
415 c, ((int **)&c)[-1]);
422 * Don't attempt to delete a callout that's not on the queue. The
423 * callout may not have a cpu assigned to it. Callers do not have
424 * to be on the issuing cpu but must still serialize access to the
427 * We are not cpu-localized here and cannot safely modify the
428 * flags field in the callout structure. Note that most of the
429 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
431 * If we race another cpu's dispatch of this callout it is possible
432 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
433 * will cause us to fall through and synchronize with the other
436 if ((c->c_flags & CALLOUT_PENDING) == 0) {
438 if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
442 if (c->c_gd == NULL || c->c_gd == gd) {
443 c->c_flags &= ~CALLOUT_ACTIVE;
447 /* fall-through to the cpu-localization code. */
449 c->c_flags &= ~CALLOUT_ACTIVE;
455 if ((tgd = c->c_gd) != gd) {
457 * If the callout is owned by a different CPU we have to
458 * execute the function synchronously on the target cpu.
462 cpu_ccfence(); /* don't let tgd alias c_gd */
463 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
464 lwkt_wait_ipiq(tgd, seq);
469 * If the callout is owned by the same CPU we can
470 * process it directly, but if we are racing our helper
471 * thread (sc->next), we have to adjust sc->next. The
472 * race is interlocked by a critical section.
474 sc = &softclock_pcpu_ary[gd->gd_cpuid];
476 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
478 sc->next = TAILQ_NEXT(c, c_links.tqe);
480 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
489 * Issue a callout_stop() and ensure that any callout race completes
490 * before returning. Does NOT de-initialized the callout.
493 callout_stop_sync(struct callout *c)
497 while (c->c_flags & CALLOUT_DID_INIT) {
501 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
502 if (sc->running == c) {
503 while (sc->running == c)
504 tsleep(&sc->running, 0, "crace", 1);
508 sc = &softclock_pcpu_ary[0];
509 if (sc->running == c) {
510 while (sc->running == c)
511 tsleep(&sc->running, 0, "crace", 1);
514 if ((c->c_flags & (CALLOUT_PENDING | CALLOUT_ACTIVE)) == 0)
516 kprintf("Warning: %s: callout race\n", curthread->td_comm);
521 * Terminate a callout
523 * This function will stop any pending callout and also block while the
524 * callout's function is running. It should only be used in cases where
525 * no deadlock is possible (due to the callout function acquiring locks
526 * that the current caller of callout_terminate() already holds), when
527 * the caller is ready to destroy the callout structure.
529 * This function clears the CALLOUT_DID_INIT flag.
531 * lwkt_token locks are ok.
534 callout_terminate(struct callout *c)
538 if (c->c_flags & CALLOUT_DID_INIT) {
541 sc = &softclock_pcpu_ary[c->c_gd->gd_cpuid];
543 sc = &softclock_pcpu_ary[0];
545 if (sc->running == c) {
546 while (sc->running == c)
547 tsleep(&sc->running, 0, "crace", 1);
549 KKASSERT((c->c_flags & (CALLOUT_PENDING|CALLOUT_ACTIVE)) == 0);
550 c->c_flags &= ~CALLOUT_DID_INIT;
555 * Prepare a callout structure for use by callout_reset() and/or
556 * callout_stop(). The MP version of this routine requires that the callback
557 * function installed by callout_reset() be MP safe.
559 * The init functions can be called from any cpu and do not have to be
560 * called from the cpu that the timer will eventually run on.
563 callout_init(struct callout *c)
566 c->c_flags = CALLOUT_DID_INIT;
570 callout_init_mp(struct callout *c)
573 c->c_flags |= CALLOUT_MPSAFE;
576 /* What, are you joking? This is nuts! -Matt */
578 #ifdef APM_FIXUP_CALLTODO
580 * Adjust the kernel calltodo timeout list. This routine is used after
581 * an APM resume to recalculate the calltodo timer list values with the
582 * number of hz's we have been sleeping. The next hardclock() will detect
583 * that there are fired timers and run softclock() to execute them.
585 * Please note, I have not done an exhaustive analysis of what code this
586 * might break. I am motivated to have my select()'s and alarm()'s that
587 * have expired during suspend firing upon resume so that the applications
588 * which set the timer can do the maintanence the timer was for as close
589 * as possible to the originally intended time. Testing this code for a
590 * week showed that resuming from a suspend resulted in 22 to 25 timers
591 * firing, which seemed independant on whether the suspend was 2 hours or
592 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
595 adjust_timeout_calltodo(struct timeval *time_change)
598 unsigned long delta_ticks;
601 * How many ticks were we asleep?
602 * (stolen from tvtohz()).
605 /* Don't do anything */
606 if (time_change->tv_sec < 0)
608 else if (time_change->tv_sec <= LONG_MAX / 1000000)
609 delta_ticks = (time_change->tv_sec * 1000000 +
610 time_change->tv_usec + (tick - 1)) / tick + 1;
611 else if (time_change->tv_sec <= LONG_MAX / hz)
612 delta_ticks = time_change->tv_sec * hz +
613 (time_change->tv_usec + (tick - 1)) / tick + 1;
615 delta_ticks = LONG_MAX;
617 if (delta_ticks > INT_MAX)
618 delta_ticks = INT_MAX;
621 * Now rip through the timer calltodo list looking for timers
625 /* don't collide with softclock() */
627 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
628 p->c_time -= delta_ticks;
630 /* Break if the timer had more time on it than delta_ticks */
634 /* take back the ticks the timer didn't use (p->c_time <= 0) */
635 delta_ticks = -p->c_time;
641 #endif /* APM_FIXUP_CALLTODO */