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>
108 #include <sys/thread2.h>
110 #ifndef MAX_SOFTCLOCK_STEPS
111 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
115 struct softclock_pcpu {
116 struct callout_tailq *callwheel;
117 struct callout * volatile next;
118 int softticks; /* softticks index */
119 int curticks; /* per-cpu ticks counter */
121 struct thread thread;
125 typedef struct softclock_pcpu *softclock_pcpu_t;
129 * allocate more timeout table slots when table overflows.
131 static MALLOC_DEFINE(M_CALLOUT, "callout", "callout structures");
132 static int callwheelsize;
133 static int callwheelbits;
134 static int callwheelmask;
135 static struct softclock_pcpu softclock_pcpu_ary[MAXCPU];
137 static void softclock_handler(void *arg);
140 swi_softclock_setup(void *arg)
146 * Figure out how large a callwheel we need. It must be a power of 2.
150 while (callwheelsize < ncallout) {
154 callwheelmask = callwheelsize - 1;
157 * Initialize per-cpu data structures.
159 for (cpu = 0; cpu < ncpus; ++cpu) {
162 sc = &softclock_pcpu_ary[cpu];
164 sc->callwheel = kmalloc(sizeof(*sc->callwheel) * callwheelsize,
165 M_CALLOUT, M_WAITOK|M_ZERO);
166 for (i = 0; i < callwheelsize; ++i)
167 TAILQ_INIT(&sc->callwheel[i]);
170 * Create a preemption-capable thread for each cpu to handle
171 * softclock timeouts on that cpu. The preemption can only
172 * be blocked by a critical section. The thread can itself
173 * be preempted by normal interrupts.
175 lwkt_create(softclock_handler, sc, NULL,
176 &sc->thread, TDF_STOPREQ|TDF_INTTHREAD, cpu,
177 "softclock %d", cpu);
180 * Do not make the thread preemptable until we clean up all
181 * the splsoftclock() calls in the system. Since the threads
182 * are no longer operated as a software interrupt, the
183 * splsoftclock() calls will not have any effect on them.
185 sc->thread.td_preemptable = lwkt_preempt;
191 * Must occur after ncpus has been initialized.
193 SYSINIT(softclock_setup, SI_BOOT2_SOFTCLOCK, SI_ORDER_SECOND,
194 swi_softclock_setup, NULL);
197 * This routine is called from the hardclock() (basically a FASTint/IPI) on
198 * each cpu in the system. sc->curticks is this cpu's notion of the timebase.
199 * It IS NOT NECESSARILY SYNCHRONIZED WITH 'ticks'! sc->softticks is where
200 * the callwheel is currently indexed.
202 * WARNING! The MP lock is not necessarily held on call, nor can it be
205 * sc->softticks is adjusted by either this routine or our helper thread
206 * depending on whether the helper thread is running or not.
209 hardclock_softtick(globaldata_t gd)
213 sc = &softclock_pcpu_ary[gd->gd_cpuid];
217 if (sc->softticks == sc->curticks) {
219 * in sync, only wakeup the thread if there is something to
222 if (TAILQ_FIRST(&sc->callwheel[sc->softticks & callwheelmask]))
225 lwkt_schedule(&sc->thread);
231 * out of sync, wakeup the thread unconditionally so it can
235 lwkt_schedule(&sc->thread);
240 * This procedure is the main loop of our per-cpu helper thread. The
241 * sc->isrunning flag prevents us from racing hardclock_softtick() and
242 * a critical section is sufficient to interlock sc->curticks and protect
243 * us from remote IPI's / list removal.
245 * The thread starts with the MP lock held and not in a critical section.
246 * The loop itself is MP safe while individual callbacks may or may not
247 * be, so we obtain or release the MP lock as appropriate.
250 softclock_handler(void *arg)
254 struct callout_tailq *bucket;
255 void (*c_func)(void *);
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);
302 KKASSERT(c->c_flags & CALLOUT_DID_INIT);
303 c->c_flags &= ~CALLOUT_PENDING;
307 /* NOTE: list may have changed */
312 lwkt_deschedule_self(&sc->thread); /* == curthread */
319 * New interface; clients allocate their own callout structures.
321 * callout_reset() - establish or change a timeout
322 * callout_stop() - disestablish a timeout
323 * callout_init() - initialize a callout structure so that it can
324 * safely be passed to callout_reset() and callout_stop()
325 * callout_init_mp() - same but any installed functions must be MP safe.
327 * <sys/callout.h> defines three convenience macros:
329 * callout_active() - returns truth if callout has not been serviced
330 * callout_pending() - returns truth if callout is still waiting for timeout
331 * callout_deactivate() - marks the callout as having been serviced
335 * Start or restart a timeout. Install the callout structure in the
336 * callwheel. Callers may legally pass any value, even if 0 or negative,
337 * but since the sc->curticks index may have already been processed a
338 * minimum timeout of 1 tick will be enforced.
340 * The callout is installed on and will be processed on the current cpu's
343 * WARNING! This function may be called from any cpu but the caller must
344 * serialize callout_stop() and callout_reset() calls on the passed
345 * structure regardless of cpu.
348 callout_reset(struct callout *c, int to_ticks, void (*ftn)(void *),
355 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
358 "callout_reset(%p) from %p: callout was not initialized\n",
359 c, ((int **)&c)[-1]);
364 sc = &softclock_pcpu_ary[gd->gd_cpuid];
367 if (c->c_flags & CALLOUT_PENDING)
374 c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
376 c->c_time = sc->curticks + to_ticks;
381 TAILQ_INSERT_TAIL(&sc->callwheel[c->c_time & callwheelmask],
387 * Stop a running timer. WARNING! If called on a cpu other then the one
388 * the callout was started on this function will liveloop on its IPI to
389 * the target cpu to process the request. It is possible for the callout
390 * to execute in that case.
392 * WARNING! This function may be called from any cpu but the caller must
393 * serialize callout_stop() and callout_reset() calls on the passed
394 * structure regardless of cpu.
396 * WARNING! This routine may be called from an IPI
399 callout_stop(struct callout *c)
401 globaldata_t gd = mycpu;
408 if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
411 "callout_stop(%p) from %p: callout was not initialized\n",
412 c, ((int **)&c)[-1]);
419 * Don't attempt to delete a callout that's not on the queue. The
420 * callout may not have a cpu assigned to it. Callers do not have
421 * to be on the issuing cpu but must still serialize access to the
424 * We are not cpu-localized here and cannot safely modify the
425 * flags field in the callout structure. Note that most of the
426 * time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
428 * If we race another cpu's dispatch of this callout it is possible
429 * for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
430 * will cause us to fall through and synchronize with the other
433 if ((c->c_flags & CALLOUT_PENDING) == 0) {
435 if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
439 if (c->c_gd == NULL || c->c_gd == gd) {
440 c->c_flags &= ~CALLOUT_ACTIVE;
444 /* fall-through to the cpu-localization code. */
446 c->c_flags &= ~CALLOUT_ACTIVE;
452 if ((tgd = c->c_gd) != gd) {
454 * If the callout is owned by a different CPU we have to
455 * execute the function synchronously on the target cpu.
459 cpu_ccfence(); /* don't let tgd alias c_gd */
460 seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
461 lwkt_wait_ipiq(tgd, seq);
466 * If the callout is owned by the same CPU we can
467 * process it directly, but if we are racing our helper
468 * thread (sc->next), we have to adjust sc->next. The
469 * race is interlocked by a critical section.
471 sc = &softclock_pcpu_ary[gd->gd_cpuid];
473 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
475 sc->next = TAILQ_NEXT(c, c_links.tqe);
477 TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
486 * Prepare a callout structure for use by callout_reset() and/or
487 * callout_stop(). The MP version of this routine requires that the callback
488 * function installed by callout_reset() be MP safe.
491 callout_init(struct callout *c)
494 c->c_flags = CALLOUT_DID_INIT;
498 callout_init_mp(struct callout *c)
501 c->c_flags |= CALLOUT_MPSAFE;
504 /* What, are you joking? This is nuts! -Matt */
506 #ifdef APM_FIXUP_CALLTODO
508 * Adjust the kernel calltodo timeout list. This routine is used after
509 * an APM resume to recalculate the calltodo timer list values with the
510 * number of hz's we have been sleeping. The next hardclock() will detect
511 * that there are fired timers and run softclock() to execute them.
513 * Please note, I have not done an exhaustive analysis of what code this
514 * might break. I am motivated to have my select()'s and alarm()'s that
515 * have expired during suspend firing upon resume so that the applications
516 * which set the timer can do the maintanence the timer was for as close
517 * as possible to the originally intended time. Testing this code for a
518 * week showed that resuming from a suspend resulted in 22 to 25 timers
519 * firing, which seemed independant on whether the suspend was 2 hours or
520 * 2 days. Your milage may vary. - Ken Key <key@cs.utk.edu>
523 adjust_timeout_calltodo(struct timeval *time_change)
526 unsigned long delta_ticks;
529 * How many ticks were we asleep?
530 * (stolen from tvtohz()).
533 /* Don't do anything */
534 if (time_change->tv_sec < 0)
536 else if (time_change->tv_sec <= LONG_MAX / 1000000)
537 delta_ticks = (time_change->tv_sec * 1000000 +
538 time_change->tv_usec + (tick - 1)) / tick + 1;
539 else if (time_change->tv_sec <= LONG_MAX / hz)
540 delta_ticks = time_change->tv_sec * hz +
541 (time_change->tv_usec + (tick - 1)) / tick + 1;
543 delta_ticks = LONG_MAX;
545 if (delta_ticks > INT_MAX)
546 delta_ticks = INT_MAX;
549 * Now rip through the timer calltodo list looking for timers
553 /* don't collide with softclock() */
555 for (p = calltodo.c_next; p != NULL; p = p->c_next) {
556 p->c_time -= delta_ticks;
558 /* Break if the timer had more time on it than delta_ticks */
562 /* take back the ticks the timer didn't use (p->c_time <= 0) */
563 delta_ticks = -p->c_time;
569 #endif /* APM_FIXUP_CALLTODO */