2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1982, 1986, 1990, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
42 #include "opt_ktrace.h"
43 #include "opt_sched.h"
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/blockcount.h>
48 #include <sys/condvar.h>
50 #include <sys/kernel.h>
53 #include <sys/mutex.h>
55 #include <sys/resourcevar.h>
56 #include <sys/sched.h>
58 #include <sys/signalvar.h>
59 #include <sys/sleepqueue.h>
62 #include <sys/sysctl.h>
63 #include <sys/sysproto.h>
64 #include <sys/vmmeter.h>
67 #include <sys/ktrace.h>
70 #include <sys/epoch.h>
73 #include <machine/cpu.h>
75 static void synch_setup(void *dummy);
76 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
80 static const char pause_wchan[MAXCPU];
82 static struct callout loadav_callout;
84 struct loadavg averunnable =
85 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
87 * Constants for averages over 1, 5, and 15 minutes
88 * when sampling at 5 second intervals.
90 static fixpt_t cexp[3] = {
91 0.9200444146293232 * FSCALE, /* exp(-1/12) */
92 0.9834714538216174 * FSCALE, /* exp(-1/60) */
93 0.9944598480048967 * FSCALE, /* exp(-1/180) */
96 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
97 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE,
98 "Fixed-point scale factor used for calculating load average values");
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, NULL);
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(const void *ident, struct lock_object *lock, int priority,
136 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
139 struct lock_class *class;
140 uintptr_t lock_state;
141 int catch, pri, rval, sleepq_flags;
142 WITNESS_SAVE_DECL(lock_witness);
146 if (KTRPOINT(td, KTR_CSW))
149 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
150 "Sleeping on \"%s\"", wmesg);
151 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL ||
152 (priority & PNOLOCK) != 0,
153 ("sleeping without a lock"));
154 KASSERT(ident != NULL, ("_sleep: NULL ident"));
155 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
156 if (priority & PDROP)
157 KASSERT(lock != NULL && lock != &Giant.lock_object,
158 ("PDROP requires a non-Giant lock"));
160 class = LOCK_CLASS(lock);
164 if (SCHEDULER_STOPPED_TD(td)) {
165 if (lock != NULL && priority & PDROP)
166 class->lc_unlock(lock);
169 catch = priority & PCATCH;
170 pri = priority & PRIMASK;
172 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));
174 if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] &&
175 (uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1])
176 sleepq_flags = SLEEPQ_PAUSE;
178 sleepq_flags = SLEEPQ_SLEEP;
180 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
183 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
184 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
186 if (lock == &Giant.lock_object)
187 mtx_assert(&Giant, MA_OWNED);
189 if (lock != NULL && lock != &Giant.lock_object &&
190 !(class->lc_flags & LC_SLEEPABLE)) {
191 WITNESS_SAVE(lock, lock_witness);
192 lock_state = class->lc_unlock(lock);
194 /* GCC needs to follow the Yellow Brick Road */
198 * We put ourselves on the sleep queue and start our timeout
199 * before calling thread_suspend_check, as we could stop there,
200 * and a wakeup or a SIGCONT (or both) could occur while we were
201 * stopped without resuming us. Thus, we must be ready for sleep
202 * when cursig() is called. If the wakeup happens while we're
203 * stopped, then td will no longer be on a sleep queue upon
204 * return from cursig().
206 sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
208 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
209 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
210 sleepq_release(ident);
211 WITNESS_SAVE(lock, lock_witness);
212 lock_state = class->lc_unlock(lock);
215 if (sbt != 0 && catch)
216 rval = sleepq_timedwait_sig(ident, pri);
218 rval = sleepq_timedwait(ident, pri);
220 rval = sleepq_wait_sig(ident, pri);
222 sleepq_wait(ident, pri);
226 if (KTRPOINT(td, KTR_CSW))
230 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
231 class->lc_lock(lock, lock_state);
232 WITNESS_RESTORE(lock, lock_witness);
238 msleep_spin_sbt(const void *ident, struct mtx *mtx, const char *wmesg,
239 sbintime_t sbt, sbintime_t pr, int flags)
243 WITNESS_SAVE_DECL(mtx);
246 KASSERT(mtx != NULL, ("sleeping without a mutex"));
247 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
248 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));
250 if (SCHEDULER_STOPPED_TD(td))
254 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
255 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
258 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
259 WITNESS_SAVE(&mtx->lock_object, mtx);
260 mtx_unlock_spin(mtx);
263 * We put ourselves on the sleep queue and start our timeout.
265 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
267 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
270 * Can't call ktrace with any spin locks held so it can lock the
271 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
272 * any spin lock. Thus, we have to drop the sleepq spin lock while
273 * we handle those requests. This is safe since we have placed our
274 * thread on the sleep queue already.
277 if (KTRPOINT(td, KTR_CSW)) {
278 sleepq_release(ident);
284 sleepq_release(ident);
285 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
290 rval = sleepq_timedwait(ident, 0);
292 sleepq_wait(ident, 0);
296 if (KTRPOINT(td, KTR_CSW))
301 WITNESS_RESTORE(&mtx->lock_object, mtx);
306 * pause_sbt() delays the calling thread by the given signed binary
307 * time. During cold bootup, pause_sbt() uses the DELAY() function
308 * instead of the _sleep() function to do the waiting. The "sbt"
309 * argument must be greater than or equal to zero. A "sbt" value of
310 * zero is equivalent to a "sbt" value of one tick.
313 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
315 KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0"));
317 /* silently convert invalid timeouts */
321 if ((cold && curthread == &thread0) || kdb_active ||
322 SCHEDULER_STOPPED()) {
324 * We delay one second at a time to avoid overflowing the
325 * system specific DELAY() function(s):
327 while (sbt >= SBT_1S) {
331 /* Do the delay remainder, if any */
332 sbt = howmany(sbt, SBT_1US);
335 return (EWOULDBLOCK);
337 return (_sleep(&pause_wchan[curcpu], NULL,
338 (flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags));
342 * Make all threads sleeping on the specified identifier runnable.
345 wakeup(const void *ident)
350 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
351 sleepq_release(ident);
352 if (wakeup_swapper) {
353 KASSERT(ident != &proc0,
354 ("wakeup and wakeup_swapper and proc0"));
360 * Make a thread sleeping on the specified identifier runnable.
361 * May wake more than one thread if a target thread is currently
365 wakeup_one(const void *ident)
370 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0);
376 wakeup_any(const void *ident)
381 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR |
388 * Signal sleeping waiters after the counter has reached zero.
391 _blockcount_wakeup(blockcount_t *bc, u_int old)
394 KASSERT(_BLOCKCOUNT_WAITERS(old),
395 ("%s: no waiters on %p", __func__, bc));
397 if (atomic_cmpset_int(&bc->__count, _BLOCKCOUNT_WAITERS_FLAG, 0))
402 * Wait for a wakeup or a signal. This does not guarantee that the count is
403 * still zero on return. Callers wanting a precise answer should use
404 * blockcount_wait() with an interlock.
406 * If there is no work to wait for, return 0. If the sleep was interrupted by a
407 * signal, return EINTR or ERESTART, and return EAGAIN otherwise.
410 _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
414 uintptr_t lock_state;
419 KASSERT(lock != &Giant.lock_object,
420 ("%s: cannot use Giant as the interlock", __func__));
422 catch = (prio & PCATCH) != 0;
423 drop = (prio & PDROP) != 0;
427 * Synchronize with the fence in blockcount_release(). If we end up
428 * waiting, the sleepqueue lock acquisition will provide the required
431 * If there is no work to wait for, but waiters are present, try to put
432 * ourselves to sleep to avoid jumping ahead.
434 if (atomic_load_acq_int(&bc->__count) == 0) {
435 if (lock != NULL && drop)
436 LOCK_CLASS(lock)->lc_unlock(lock);
444 lock_state = LOCK_CLASS(lock)->lc_unlock(lock);
445 old = blockcount_read(bc);
448 if (_BLOCKCOUNT_COUNT(old) == 0) {
449 sleepq_release(wchan);
452 if (_BLOCKCOUNT_WAITERS(old))
454 } while (!atomic_fcmpset_int(&bc->__count, &old,
455 old | _BLOCKCOUNT_WAITERS_FLAG));
456 sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0);
458 ret = sleepq_wait_sig(wchan, prio);
460 sleepq_wait(wchan, prio);
466 if (lock != NULL && !drop)
467 LOCK_CLASS(lock)->lc_lock(lock, lock_state);
475 thread_unlock(curthread);
478 panic("%s: did not reenter debugger", __func__);
482 * The machine independent parts of context switching.
484 * The thread lock is required on entry and is no longer held on return.
489 uint64_t runtime, new_switchtime;
492 td = curthread; /* XXX */
493 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
494 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
496 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
497 mtx_assert(&Giant, MA_NOTOWNED);
499 KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(),
500 ("mi_switch: switch in a critical section"));
501 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
502 ("mi_switch: switch must be voluntary or involuntary"));
505 * Don't perform context switches from the debugger.
509 if (SCHEDULER_STOPPED_TD(td))
511 if (flags & SW_VOL) {
512 td->td_ru.ru_nvcsw++;
513 td->td_swvoltick = ticks;
515 td->td_ru.ru_nivcsw++;
516 td->td_swinvoltick = ticks;
519 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
522 * Compute the amount of time during which the current
523 * thread was running, and add that to its total so far.
525 new_switchtime = cpu_ticks();
526 runtime = new_switchtime - PCPU_GET(switchtime);
527 td->td_runtime += runtime;
528 td->td_incruntime += runtime;
529 PCPU_SET(switchtime, new_switchtime);
530 td->td_generation++; /* bump preempt-detect counter */
532 PCPU_SET(switchticks, ticks);
533 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
534 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
536 if (SDT_PROBES_ENABLED() &&
537 ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
538 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED)))
539 SDT_PROBE0(sched, , , preempt);
541 sched_switch(td, flags);
542 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
543 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
546 * If the last thread was exiting, finish cleaning it up.
548 if ((td = PCPU_GET(deadthread))) {
549 PCPU_SET(deadthread, NULL);
556 * Change thread state to be runnable, placing it on the run queue if
557 * it is in memory. If it is swapped out, return true so our caller
558 * will know to awaken the swapper.
560 * Requires the thread lock on entry, drops on exit.
563 setrunnable(struct thread *td, int srqflags)
567 THREAD_LOCK_ASSERT(td, MA_OWNED);
568 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
569 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
572 switch (TD_GET_STATE(td)) {
577 KASSERT((td->td_flags & TDF_INMEM) != 0,
578 ("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X",
579 td, td->td_flags, td->td_inhibitors));
580 /* unlocks thread lock according to flags */
581 sched_wakeup(td, srqflags);
585 * If we are only inhibited because we are swapped out
586 * arrange to swap in this process.
588 if (td->td_inhibitors == TDI_SWAPPED &&
589 (td->td_flags & TDF_SWAPINREQ) == 0) {
590 td->td_flags |= TDF_SWAPINREQ;
595 panic("setrunnable: state 0x%x", TD_GET_STATE(td));
597 if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0)
604 * Compute a tenex style load average of a quantity on
605 * 1, 5 and 15 minute intervals.
616 for (i = 0; i < 3; i++)
617 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
618 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
621 * Schedule the next update to occur after 5 seconds, but add a
622 * random variation to avoid synchronisation with processes that
623 * run at regular intervals.
625 callout_reset_sbt(&loadav_callout,
626 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
627 loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
632 synch_setup(void *dummy)
634 callout_init(&loadav_callout, 1);
636 /* Kick off timeout driven events by calling first time. */
644 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
652 kern_yield(PRI_USER);
663 if (prio == PRI_USER)
664 prio = td->td_user_pri;
666 sched_prio(td, prio);
667 mi_switch(SW_VOL | SWT_RELINQUISH);
672 * General purpose yield system call.
675 sys_yield(struct thread *td, struct yield_args *uap)
679 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
680 sched_prio(td, PRI_MAX_TIMESHARE);
681 mi_switch(SW_VOL | SWT_RELINQUISH);
682 td->td_retval[0] = 0;