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 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 callwheelbits;
136 static int callwheelmask;
137 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU];
139 static void softclock_handler(void *arg);
142 swi_softclock_setup(void *arg)
148 * Figure out how large a callwheel we need. It must be a power of 2.
152 while (callwheelsize < ncallout) {
156 callwheelmask = callwheelsize - 1;
159 * Initialize per-cpu data structures.
161 for (cpu = 0; cpu < ncpus; ++cpu) {
164 sc = &softclock_pcpu_ary[cpu];
166 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize,
167 M_CALLOUT, M_WAITOK|M_ZERO);
168 for (i = 0; i < callwheelsize; ++i)
169 TAILQ_INIT(&sc->callwheel[i]);
172 * Mark the softclock handler as being an interrupt thread
173 * even though it really isn't, but do not allow it to
174 * preempt other threads (do not assign td_preemptable).
176 * Kernel code now assumes that callouts do not preempt
177 * the cpu they were scheduled on.
179 lwkt_create(softclock_handler, sc, NULL,
180 &sc->thread, TDF_STOPREQ | TDF_INTTHREAD,
181 cpu, "softclock %d", cpu);
186 * Must occur after ncpus has been initialized.
188 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND,
189 swi_softclock_setup, NULL);
192 * This routine is called from the hardclock() (basically a FASTint/IPI) on
193 * each cpu in the system. sc->curticks is this cpu's notion of the timebase.
194 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where
195 * the callwheel is currently indexed.
197 * WARNING! The MP lock is not necessarily held on call, nor can it be
200 * sc->softticks is adjusted by either this routine or our helper thread
201 * depending on whether the helper thread is running or not.
204 hardclock_softtick(globaldata_t gd)
208 sc = &softclock_pcpu_ary[gd->gd_cpuid];
212 if (sc->softticks == sc->curticks) {
214 * in sync, only wakeup the thread if there is something to
217 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask]))
220 lwkt_schedule(&sc->thread);
226 * out of sync, wakeup the thread unconditionally so it can
230 lwkt_schedule(&sc->thread);
235 * This procedure is the main loop of our per-cpu helper thread. The
236 * sc->isrunning flag prevents us from racing hardclock_softtick() and
237 * a critical section is sufficient to interlock sc->curticks and protect
238 * us from remote IPI's / list removal.
240 * The thread starts with the MP lock released and not in a critical
241 * section. The loop itself is MP safe while individual callbacks
242 * may or may not be, so we obtain or release the MP lock as appropriate.
245 softclock_handler(void *arg)
249 struct callout_tailq *bucket;
250 void (*c_func)(void *);
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);
297 KKASSERT(c->c_flags & CALLOUT_DID_INIT);
298 c->c_flags &= ~CALLOUT_PENDING;
302 /* NOTE: list may have changed */
307 lwkt_deschedule_self(&sc->thread); /* == curthread */
314 * New interface; clients allocate their own callout structures.
316 * callout_reset() - establish or change a timeout
317 * callout_stop() - disestablish a timeout
318 * callout_init() - initialize a callout structure so that it can
319 * safely be passed to callout_reset() and callout_stop()
320 * callout_init_mp() - same but any installed functions must be MP safe.
322 * <sys/callout.h> defines three convenience macros:
324 * callout_active() - returns truth if callout has not been serviced
325 * callout_pending() - returns truth if callout is still waiting for timeout
326 * callout_deactivate() - marks the callout as having been serviced
330 * Start or restart a timeout. Install the callout structure in the
331 * callwheel. Callers may legally pass any value, even if 0 or negative,
332 * but since the sc->curticks index may have already been processed a
333 * minimum timeout of 1 tick will be enforced.
335 * The callout is installed on and will be processed on the current cpu's
338 * WARNING! This function may be called from any cpu but the caller must
339 * serialize callout_stop() and callout_reset() calls on the passed
340 * structure regardless of cpu.
343 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
350 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
353 "callout_reset(%p) from %p: callout was not initialized\n",
354 c, ((int **)&c)[-1]);
359 sc = &softclock_pcpu_ary[gd->gd_cpuid];
362 if (c->c_flags & CALLOUT_PENDING)
369 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
371 c->c_time = sc->curticks + to_ticks;
376 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask],
382 * Stop a running timer. WARNING! If called on a cpu other then the one
383 * the callout was started on this function will liveloop on its IPI to
384 * the target cpu to process the request. It is possible for the callout
385 * to execute in that case.
387 * WARNING! This function may be called from any cpu but the caller must
388 * serialize callout_stop() and callout_reset() calls on the passed
389 * structure regardless of cpu.
391 * WARNING! This routine may be called from an IPI
394 callout_stop(struct callout *c)
396 globaldata_t gd = mycpu;
403 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
406 "callout_stop(%p) from %p: callout was not initialized\n",
407 c, ((int **)&c)[-1]);
414 * Don't attempt to delete a callout that's not on the queue. The
415 * callout may not have a cpu assigned to it. Callers do not have
416 * to be on the issuing cpu but must still serialize access to the
419 * We are not cpu-localized here and cannot safely modify the
420 * flags field in the callout structure. Note that most of the
421 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
423 * If we race another cpu's dispatch of this callout it is possible
424 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
425 * will cause us to fall through and synchronize with the other
428 if ((c->c_flags & CALLOUT_PENDING) == 0) {
430 if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
434 if (c->c_gd == NULL || c->c_gd == gd) {
435 c->c_flags &= ~CALLOUT_ACTIVE;
439 /* fall-through to the cpu-localization code. */
441 c->c_flags &= ~CALLOUT_ACTIVE;
447 if ((tgd = c->c_gd) != gd) {
449 * If the callout is owned by a different CPU we have to
450 * execute the function synchronously on the target cpu.
454 cpu_ccfence(); /* don't let tgd alias c_gd */
455 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
456 lwkt_wait_ipiq(tgd, seq);
461 * If the callout is owned by the same CPU we can
462 * process it directly, but if we are racing our helper
463 * thread (sc->next), we have to adjust sc->next. The
464 * race is interlocked by a critical section.
466 sc = &softclock_pcpu_ary[gd->gd_cpuid];
468 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
470 sc->next = TAILQ_NEXT(c, c_links.tqe);
472 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
481 * Prepare a callout structure for use by callout_reset() and/or
482 * callout_stop(). The MP version of this routine requires that the callback
483 * function installed by callout_reset() be MP safe.
485 * The init functions can be called from any cpu and do not have to be
486 * called from the cpu that the timer will eventually run on.
489 callout_init(struct callout *c)
492 c->c_flags = CALLOUT_DID_INIT;
496 callout_init_mp(struct callout *c)
499 c->c_flags |= CALLOUT_MPSAFE;
502 /* What, are you joking? This is nuts! -Matt */
504 #ifdef APM_FIXUP_CALLTODO
506 * Adjust the kernel calltodo timeout list. This routine is used after
507 * an APM resume to recalculate the calltodo timer list values with the
508 * number of hz's we have been sleeping. The next hardclock() will detect
509 * that there are fired timers and run softclock() to execute them.
511 * Please note, I have not done an exhaustive analysis of what code this
512 * might break. I am motivated to have my select()'s and alarm()'s that
513 * have expired during suspend firing upon resume so that the applications
514 * which set the timer can do the maintanence the timer was for as close
515 * as possible to the originally intended time. Testing this code for a
516 * week showed that resuming from a suspend resulted in 22 to 25 timers
517 * firing, which seemed independant on whether the suspend was 2 hours or
518 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
521 adjust_timeout_calltodo(struct timeval *time_change)
524 unsigned long delta_ticks;
527 * How many ticks were we asleep?
528 * (stolen from tvtohz()).
531 /* Don't do anything */
532 if (time_change->tv_sec < 0)
534 else if (time_change->tv_sec <= LONG_MAX / 1000000)
535 delta_ticks = (time_change->tv_sec * 1000000 +
536 time_change->tv_usec + (tick - 1)) / tick + 1;
537 else if (time_change->tv_sec <= LONG_MAX / hz)
538 delta_ticks = time_change->tv_sec * hz +
539 (time_change->tv_usec + (tick - 1)) / tick + 1;
541 delta_ticks = LONG_MAX;
543 if (delta_ticks > INT_MAX)
544 delta_ticks = INT_MAX;
547 * Now rip through the timer calltodo list looking for timers
551 /* don't collide with softclock() */
553 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
554 p->c_time -= delta_ticks;
556 /* Break if the timer had more time on it than delta_ticks */
560 /* take back the ticks the timer didn't use (p->c_time <= 0) */
561 delta_ticks = -p->c_time;
567 #endif /* APM_FIXUP_CALLTODO */