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34 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
40 #include "opt_ktrace.h"
41 #include "opt_sched.h"
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/condvar.h>
47 #include <sys/kernel.h>
50 #include <sys/mutex.h>
52 #include <sys/resourcevar.h>
53 #include <sys/sched.h>
55 #include <sys/signalvar.h>
56 #include <sys/sleepqueue.h>
59 #include <sys/sysctl.h>
60 #include <sys/sysproto.h>
61 #include <sys/vmmeter.h>
64 #include <sys/ktrace.h>
67 #include <machine/cpu.h>
69 #define KTDSTATE(td) \
70 (((td)->td_inhibitors & TDI_SLEEPING) != 0 ? "sleep" : \
71 ((td)->td_inhibitors & TDI_SUSPENDED) != 0 ? "suspended" : \
72 ((td)->td_inhibitors & TDI_SWAPPED) != 0 ? "swapped" : \
73 ((td)->td_inhibitors & TDI_LOCK) != 0 ? "blocked" : \
74 ((td)->td_inhibitors & TDI_IWAIT) != 0 ? "iwait" : "yielding")
76 static void synch_setup(void *dummy);
77 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
81 static uint8_t pause_wchan[MAXCPU];
83 static struct callout loadav_callout;
85 struct loadavg averunnable =
86 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
88 * Constants for averages over 1, 5, and 15 minutes
89 * when sampling at 5 second intervals.
91 static fixpt_t cexp[3] = {
92 0.9200444146293232 * FSCALE, /* exp(-1/12) */
93 0.9834714538216174 * FSCALE, /* exp(-1/60) */
94 0.9944598480048967 * FSCALE, /* exp(-1/180) */
97 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
98 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, "");
100 static void loadav(void *arg);
102 SDT_PROVIDER_DECLARE(sched);
103 SDT_PROBE_DEFINE(sched, , , preempt);
106 sleepinit(void *unused)
109 hogticks = (hz / 10) * 2; /* Default only. */
114 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
117 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, 0);
120 * General sleep call. Suspends the current thread until a wakeup is
121 * performed on the specified identifier. The thread will then be made
122 * runnable with the specified priority. Sleeps at most sbt units of time
123 * (0 means no timeout). If pri includes the PCATCH flag, let signals
124 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if
125 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
126 * signal becomes pending, ERESTART is returned if the current system
127 * call should be restarted if possible, and EINTR is returned if the system
128 * call should be interrupted by the signal (return EINTR).
130 * The lock argument is unlocked before the caller is suspended, and
131 * re-locked before _sleep() returns. If priority includes the PDROP
132 * flag the lock is not re-locked before returning.
135 _sleep(void *ident, struct lock_object *lock, int priority,
136 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
140 struct lock_class *class;
141 uintptr_t lock_state;
142 int catch, pri, rval, sleepq_flags;
143 WITNESS_SAVE_DECL(lock_witness);
148 if (KTRPOINT(td, KTR_CSW))
151 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
152 "Sleeping on \"%s\"", wmesg);
153 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL,
154 ("sleeping without a lock"));
155 KASSERT(p != NULL, ("msleep1"));
156 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
157 if (priority & PDROP)
158 KASSERT(lock != NULL && lock != &Giant.lock_object,
159 ("PDROP requires a non-Giant lock"));
161 class = LOCK_CLASS(lock);
165 if (cold || SCHEDULER_STOPPED()) {
167 * During autoconfiguration, just return;
168 * don't run any other threads or panic below,
169 * in case this is the idle thread and already asleep.
170 * XXX: this used to do "s = splhigh(); splx(safepri);
171 * splx(s);" to give interrupts a chance, but there is
172 * no way to give interrupts a chance now.
174 if (lock != NULL && priority & PDROP)
175 class->lc_unlock(lock);
178 catch = priority & PCATCH;
179 pri = priority & PRIMASK;
182 * If we are already on a sleep queue, then remove us from that
183 * sleep queue first. We have to do this to handle recursive
186 if (TD_ON_SLEEPQ(td))
187 sleepq_remove(td, td->td_wchan);
189 if ((uint8_t *)ident >= &pause_wchan[0] &&
190 (uint8_t *)ident <= &pause_wchan[MAXCPU - 1])
191 sleepq_flags = SLEEPQ_PAUSE;
193 sleepq_flags = SLEEPQ_SLEEP;
195 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
198 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
199 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
201 if (lock == &Giant.lock_object)
202 mtx_assert(&Giant, MA_OWNED);
204 if (lock != NULL && lock != &Giant.lock_object &&
205 !(class->lc_flags & LC_SLEEPABLE)) {
206 WITNESS_SAVE(lock, lock_witness);
207 lock_state = class->lc_unlock(lock);
209 /* GCC needs to follow the Yellow Brick Road */
213 * We put ourselves on the sleep queue and start our timeout
214 * before calling thread_suspend_check, as we could stop there,
215 * and a wakeup or a SIGCONT (or both) could occur while we were
216 * stopped without resuming us. Thus, we must be ready for sleep
217 * when cursig() is called. If the wakeup happens while we're
218 * stopped, then td will no longer be on a sleep queue upon
219 * return from cursig().
221 sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
223 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
224 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
225 sleepq_release(ident);
226 WITNESS_SAVE(lock, lock_witness);
227 lock_state = class->lc_unlock(lock);
230 if (sbt != 0 && catch)
231 rval = sleepq_timedwait_sig(ident, pri);
233 rval = sleepq_timedwait(ident, pri);
235 rval = sleepq_wait_sig(ident, pri);
237 sleepq_wait(ident, pri);
241 if (KTRPOINT(td, KTR_CSW))
245 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
246 class->lc_lock(lock, lock_state);
247 WITNESS_RESTORE(lock, lock_witness);
253 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg,
254 sbintime_t sbt, sbintime_t pr, int flags)
259 WITNESS_SAVE_DECL(mtx);
263 KASSERT(mtx != NULL, ("sleeping without a mutex"));
264 KASSERT(p != NULL, ("msleep1"));
265 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
267 if (cold || SCHEDULER_STOPPED()) {
269 * During autoconfiguration, just return;
270 * don't run any other threads or panic below,
271 * in case this is the idle thread and already asleep.
272 * XXX: this used to do "s = splhigh(); splx(safepri);
273 * splx(s);" to give interrupts a chance, but there is
274 * no way to give interrupts a chance now.
280 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
281 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
284 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
285 WITNESS_SAVE(&mtx->lock_object, mtx);
286 mtx_unlock_spin(mtx);
289 * We put ourselves on the sleep queue and start our timeout.
291 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
293 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
296 * Can't call ktrace with any spin locks held so it can lock the
297 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
298 * any spin lock. Thus, we have to drop the sleepq spin lock while
299 * we handle those requests. This is safe since we have placed our
300 * thread on the sleep queue already.
303 if (KTRPOINT(td, KTR_CSW)) {
304 sleepq_release(ident);
310 sleepq_release(ident);
311 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
316 rval = sleepq_timedwait(ident, 0);
318 sleepq_wait(ident, 0);
322 if (KTRPOINT(td, KTR_CSW))
327 WITNESS_RESTORE(&mtx->lock_object, mtx);
332 * pause() delays the calling thread by the given number of system ticks.
333 * During cold bootup, pause() uses the DELAY() function instead of
334 * the tsleep() function to do the waiting. The "timo" argument must be
335 * greater than or equal to zero. A "timo" value of zero is equivalent
336 * to a "timo" value of one.
339 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
341 KASSERT(sbt >= 0, ("pause: timeout must be >= 0"));
343 /* silently convert invalid timeouts */
347 if (cold || kdb_active) {
349 * We delay one second at a time to avoid overflowing the
350 * system specific DELAY() function(s):
352 while (sbt >= SBT_1S) {
356 /* Do the delay remainder, if any */
357 sbt = (sbt + SBT_1US - 1) / SBT_1US;
362 return (_sleep(&pause_wchan[curcpu], NULL, 0, wmesg, sbt, pr, flags));
366 * Make all threads sleeping on the specified identifier runnable.
374 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
375 sleepq_release(ident);
376 if (wakeup_swapper) {
377 KASSERT(ident != &proc0,
378 ("wakeup and wakeup_swapper and proc0"));
384 * Make a thread sleeping on the specified identifier runnable.
385 * May wake more than one thread if a target thread is currently
389 wakeup_one(void *ident)
394 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
395 sleepq_release(ident);
403 thread_unlock(curthread);
406 panic("%s: did not reenter debugger", __func__);
410 * The machine independent parts of context switching.
413 mi_switch(int flags, struct thread *newtd)
415 uint64_t runtime, new_switchtime;
419 td = curthread; /* XXX */
420 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
421 p = td->td_proc; /* XXX */
422 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
424 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
425 mtx_assert(&Giant, MA_NOTOWNED);
427 KASSERT(td->td_critnest == 1 || panicstr,
428 ("mi_switch: switch in a critical section"));
429 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
430 ("mi_switch: switch must be voluntary or involuntary"));
431 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
434 * Don't perform context switches from the debugger.
438 if (SCHEDULER_STOPPED())
440 if (flags & SW_VOL) {
441 td->td_ru.ru_nvcsw++;
442 td->td_swvoltick = ticks;
444 td->td_ru.ru_nivcsw++;
446 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
449 * Compute the amount of time during which the current
450 * thread was running, and add that to its total so far.
452 new_switchtime = cpu_ticks();
453 runtime = new_switchtime - PCPU_GET(switchtime);
454 td->td_runtime += runtime;
455 td->td_incruntime += runtime;
456 PCPU_SET(switchtime, new_switchtime);
457 td->td_generation++; /* bump preempt-detect counter */
458 PCPU_INC(cnt.v_swtch);
459 PCPU_SET(switchticks, ticks);
460 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
461 td->td_tid, td->td_sched, p->p_pid, td->td_name);
462 #if (KTR_COMPILE & KTR_SCHED) != 0
463 if (TD_IS_IDLETHREAD(td))
464 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
465 "prio:%d", td->td_priority);
467 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
468 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
469 "lockname:\"%s\"", td->td_lockname);
471 SDT_PROBE0(sched, , , preempt);
472 sched_switch(td, newtd, flags);
473 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
474 "prio:%d", td->td_priority);
476 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
477 td->td_tid, td->td_sched, p->p_pid, td->td_name);
480 * If the last thread was exiting, finish cleaning it up.
482 if ((td = PCPU_GET(deadthread))) {
483 PCPU_SET(deadthread, NULL);
489 * Change thread state to be runnable, placing it on the run queue if
490 * it is in memory. If it is swapped out, return true so our caller
491 * will know to awaken the swapper.
494 setrunnable(struct thread *td)
497 THREAD_LOCK_ASSERT(td, MA_OWNED);
498 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
499 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
500 switch (td->td_state) {
506 * If we are only inhibited because we are swapped out
507 * then arange to swap in this process. Otherwise just return.
509 if (td->td_inhibitors != TDI_SWAPPED)
515 printf("state is 0x%x", td->td_state);
516 panic("setrunnable(2)");
518 if ((td->td_flags & TDF_INMEM) == 0) {
519 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
520 td->td_flags |= TDF_SWAPINREQ;
529 * Compute a tenex style load average of a quantity on
530 * 1, 5 and 15 minute intervals.
541 for (i = 0; i < 3; i++)
542 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
543 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
546 * Schedule the next update to occur after 5 seconds, but add a
547 * random variation to avoid synchronisation with processes that
548 * run at regular intervals.
550 callout_reset_sbt(&loadav_callout,
551 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
552 loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
557 synch_setup(void *dummy)
559 callout_init(&loadav_callout, CALLOUT_MPSAFE);
561 /* Kick off timeout driven events by calling first time. */
569 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
577 kern_yield(PRI_USER);
588 if (prio == PRI_USER)
589 prio = td->td_user_pri;
591 sched_prio(td, prio);
592 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
598 * General purpose yield system call.
601 sys_yield(struct thread *td, struct yield_args *uap)
605 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
606 sched_prio(td, PRI_MAX_TIMESHARE);
607 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
609 td->td_retval[0] = 0;