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/condvar.h>
49 #include <sys/kernel.h>
52 #include <sys/mutex.h>
54 #include <sys/resourcevar.h>
55 #include <sys/sched.h>
57 #include <sys/signalvar.h>
58 #include <sys/sleepqueue.h>
61 #include <sys/sysctl.h>
62 #include <sys/sysproto.h>
63 #include <sys/vmmeter.h>
66 #include <sys/ktrace.h>
69 #include <machine/cpu.h>
71 static void synch_setup(void *dummy);
72 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
76 static uint8_t pause_wchan[MAXCPU];
78 static struct callout loadav_callout;
80 struct loadavg averunnable =
81 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
83 * Constants for averages over 1, 5, and 15 minutes
84 * when sampling at 5 second intervals.
86 static fixpt_t cexp[3] = {
87 0.9200444146293232 * FSCALE, /* exp(-1/12) */
88 0.9834714538216174 * FSCALE, /* exp(-1/60) */
89 0.9944598480048967 * FSCALE, /* exp(-1/180) */
92 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
93 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, "");
95 static void loadav(void *arg);
97 SDT_PROVIDER_DECLARE(sched);
98 SDT_PROBE_DEFINE(sched, , , preempt);
101 sleepinit(void *unused)
104 hogticks = (hz / 10) * 2; /* Default only. */
109 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
112 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, 0);
115 * General sleep call. Suspends the current thread until a wakeup is
116 * performed on the specified identifier. The thread will then be made
117 * runnable with the specified priority. Sleeps at most sbt units of time
118 * (0 means no timeout). If pri includes the PCATCH flag, let signals
119 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if
120 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
121 * signal becomes pending, ERESTART is returned if the current system
122 * call should be restarted if possible, and EINTR is returned if the system
123 * call should be interrupted by the signal (return EINTR).
125 * The lock argument is unlocked before the caller is suspended, and
126 * re-locked before _sleep() returns. If priority includes the PDROP
127 * flag the lock is not re-locked before returning.
130 _sleep(void *ident, struct lock_object *lock, int priority,
131 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
135 struct lock_class *class;
136 uintptr_t lock_state;
137 int catch, pri, rval, sleepq_flags;
138 WITNESS_SAVE_DECL(lock_witness);
143 if (KTRPOINT(td, KTR_CSW))
146 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
147 "Sleeping on \"%s\"", wmesg);
148 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL,
149 ("sleeping without a lock"));
150 KASSERT(ident != NULL, ("_sleep: NULL ident"));
151 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
152 if (priority & PDROP)
153 KASSERT(lock != NULL && lock != &Giant.lock_object,
154 ("PDROP requires a non-Giant lock"));
156 class = LOCK_CLASS(lock);
160 if (SCHEDULER_STOPPED_TD(td)) {
161 if (lock != NULL && priority & PDROP)
162 class->lc_unlock(lock);
165 catch = priority & PCATCH;
166 pri = priority & PRIMASK;
168 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));
170 if ((uint8_t *)ident >= &pause_wchan[0] &&
171 (uint8_t *)ident <= &pause_wchan[MAXCPU - 1])
172 sleepq_flags = SLEEPQ_PAUSE;
174 sleepq_flags = SLEEPQ_SLEEP;
176 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
179 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
180 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
182 if (lock == &Giant.lock_object)
183 mtx_assert(&Giant, MA_OWNED);
185 if (lock != NULL && lock != &Giant.lock_object &&
186 !(class->lc_flags & LC_SLEEPABLE)) {
187 WITNESS_SAVE(lock, lock_witness);
188 lock_state = class->lc_unlock(lock);
190 /* GCC needs to follow the Yellow Brick Road */
194 * We put ourselves on the sleep queue and start our timeout
195 * before calling thread_suspend_check, as we could stop there,
196 * and a wakeup or a SIGCONT (or both) could occur while we were
197 * stopped without resuming us. Thus, we must be ready for sleep
198 * when cursig() is called. If the wakeup happens while we're
199 * stopped, then td will no longer be on a sleep queue upon
200 * return from cursig().
202 sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
204 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
205 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
206 sleepq_release(ident);
207 WITNESS_SAVE(lock, lock_witness);
208 lock_state = class->lc_unlock(lock);
211 if (sbt != 0 && catch)
212 rval = sleepq_timedwait_sig(ident, pri);
214 rval = sleepq_timedwait(ident, pri);
216 rval = sleepq_wait_sig(ident, pri);
218 sleepq_wait(ident, pri);
222 if (KTRPOINT(td, KTR_CSW))
226 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
227 class->lc_lock(lock, lock_state);
228 WITNESS_RESTORE(lock, lock_witness);
234 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg,
235 sbintime_t sbt, sbintime_t pr, int flags)
240 WITNESS_SAVE_DECL(mtx);
244 KASSERT(mtx != NULL, ("sleeping without a mutex"));
245 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
246 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));
248 if (SCHEDULER_STOPPED_TD(td))
252 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
253 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
256 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
257 WITNESS_SAVE(&mtx->lock_object, mtx);
258 mtx_unlock_spin(mtx);
261 * We put ourselves on the sleep queue and start our timeout.
263 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
265 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
268 * Can't call ktrace with any spin locks held so it can lock the
269 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
270 * any spin lock. Thus, we have to drop the sleepq spin lock while
271 * we handle those requests. This is safe since we have placed our
272 * thread on the sleep queue already.
275 if (KTRPOINT(td, KTR_CSW)) {
276 sleepq_release(ident);
282 sleepq_release(ident);
283 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
288 rval = sleepq_timedwait(ident, 0);
290 sleepq_wait(ident, 0);
294 if (KTRPOINT(td, KTR_CSW))
299 WITNESS_RESTORE(&mtx->lock_object, mtx);
304 * pause() delays the calling thread by the given number of system ticks.
305 * During cold bootup, pause() uses the DELAY() function instead of
306 * the tsleep() function to do the waiting. The "timo" argument must be
307 * greater than or equal to zero. A "timo" value of zero is equivalent
308 * to a "timo" value of one.
311 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
313 KASSERT(sbt >= 0, ("pause: timeout must be >= 0"));
315 /* silently convert invalid timeouts */
319 if ((cold && curthread == &thread0) || kdb_active ||
320 SCHEDULER_STOPPED()) {
322 * We delay one second at a time to avoid overflowing the
323 * system specific DELAY() function(s):
325 while (sbt >= SBT_1S) {
329 /* Do the delay remainder, if any */
330 sbt = howmany(sbt, SBT_1US);
335 return (_sleep(&pause_wchan[curcpu], NULL, 0, wmesg, sbt, pr, flags));
339 * Make all threads sleeping on the specified identifier runnable.
347 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
348 sleepq_release(ident);
349 if (wakeup_swapper) {
350 KASSERT(ident != &proc0,
351 ("wakeup and wakeup_swapper and proc0"));
357 * Make a thread sleeping on the specified identifier runnable.
358 * May wake more than one thread if a target thread is currently
362 wakeup_one(void *ident)
367 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
368 sleepq_release(ident);
376 thread_unlock(curthread);
379 panic("%s: did not reenter debugger", __func__);
383 * The machine independent parts of context switching.
386 mi_switch(int flags, struct thread *newtd)
388 uint64_t runtime, new_switchtime;
391 td = curthread; /* XXX */
392 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
393 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
395 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
396 mtx_assert(&Giant, MA_NOTOWNED);
398 KASSERT(td->td_critnest == 1 || panicstr,
399 ("mi_switch: switch in a critical section"));
400 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
401 ("mi_switch: switch must be voluntary or involuntary"));
402 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
405 * Don't perform context switches from the debugger.
409 if (SCHEDULER_STOPPED_TD(td))
411 if (flags & SW_VOL) {
412 td->td_ru.ru_nvcsw++;
413 td->td_swvoltick = ticks;
415 td->td_ru.ru_nivcsw++;
416 td->td_swinvoltick = ticks;
419 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
422 * Compute the amount of time during which the current
423 * thread was running, and add that to its total so far.
425 new_switchtime = cpu_ticks();
426 runtime = new_switchtime - PCPU_GET(switchtime);
427 td->td_runtime += runtime;
428 td->td_incruntime += runtime;
429 PCPU_SET(switchtime, new_switchtime);
430 td->td_generation++; /* bump preempt-detect counter */
432 PCPU_SET(switchticks, ticks);
433 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
434 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
436 if ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
437 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED))
438 SDT_PROBE0(sched, , , preempt);
440 sched_switch(td, newtd, flags);
441 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
442 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
445 * If the last thread was exiting, finish cleaning it up.
447 if ((td = PCPU_GET(deadthread))) {
448 PCPU_SET(deadthread, NULL);
454 * Change thread state to be runnable, placing it on the run queue if
455 * it is in memory. If it is swapped out, return true so our caller
456 * will know to awaken the swapper.
459 setrunnable(struct thread *td)
462 THREAD_LOCK_ASSERT(td, MA_OWNED);
463 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
464 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
465 switch (td->td_state) {
471 * If we are only inhibited because we are swapped out
472 * then arange to swap in this process. Otherwise just return.
474 if (td->td_inhibitors != TDI_SWAPPED)
480 printf("state is 0x%x", td->td_state);
481 panic("setrunnable(2)");
483 if ((td->td_flags & TDF_INMEM) == 0) {
484 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
485 td->td_flags |= TDF_SWAPINREQ;
494 * Compute a tenex style load average of a quantity on
495 * 1, 5 and 15 minute intervals.
506 for (i = 0; i < 3; i++)
507 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
508 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
511 * Schedule the next update to occur after 5 seconds, but add a
512 * random variation to avoid synchronisation with processes that
513 * run at regular intervals.
515 callout_reset_sbt(&loadav_callout,
516 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
517 loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
522 synch_setup(void *dummy)
524 callout_init(&loadav_callout, 1);
526 /* Kick off timeout driven events by calling first time. */
534 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
542 kern_yield(PRI_USER);
553 if (prio == PRI_USER)
554 prio = td->td_user_pri;
556 sched_prio(td, prio);
557 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
563 * General purpose yield system call.
566 sys_yield(struct thread *td, struct yield_args *uap)
570 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
571 sched_prio(td, PRI_MAX_TIMESHARE);
572 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
574 td->td_retval[0] = 0;