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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_kdtrace.h"
41 #include "opt_ktrace.h"
42 #include "opt_sched.h"
44 #include <sys/param.h>
45 #include <sys/systm.h>
46 #include <sys/condvar.h>
48 #include <sys/kernel.h>
51 #include <sys/mutex.h>
53 #include <sys/resourcevar.h>
54 #include <sys/sched.h>
56 #include <sys/signalvar.h>
57 #include <sys/sleepqueue.h>
60 #include <sys/sysctl.h>
61 #include <sys/sysproto.h>
62 #include <sys/vmmeter.h>
65 #include <sys/ktrace.h>
68 #include <machine/cpu.h>
72 #include <vm/vm_param.h>
76 #define KTDSTATE(td) \
77 (((td)->td_inhibitors & TDI_SLEEPING) != 0 ? "sleep" : \
78 ((td)->td_inhibitors & TDI_SUSPENDED) != 0 ? "suspended" : \
79 ((td)->td_inhibitors & TDI_SWAPPED) != 0 ? "swapped" : \
80 ((td)->td_inhibitors & TDI_LOCK) != 0 ? "blocked" : \
81 ((td)->td_inhibitors & TDI_IWAIT) != 0 ? "iwait" : "yielding")
83 static void synch_setup(void *dummy);
84 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
88 static int pause_wchan;
90 static struct callout loadav_callout;
92 struct loadavg averunnable =
93 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
95 * Constants for averages over 1, 5, and 15 minutes
96 * when sampling at 5 second intervals.
98 static fixpt_t cexp[3] = {
99 0.9200444146293232 * FSCALE, /* exp(-1/12) */
100 0.9834714538216174 * FSCALE, /* exp(-1/60) */
101 0.9944598480048967 * FSCALE, /* exp(-1/180) */
104 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
105 static int fscale __unused = FSCALE;
106 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
108 static void loadav(void *arg);
110 SDT_PROVIDER_DECLARE(sched);
111 SDT_PROBE_DEFINE(sched, , , preempt, preempt);
114 * These probes reference Solaris features that are not implemented in FreeBSD.
115 * Create the probes anyway for compatibility with existing D scripts; they'll
118 SDT_PROBE_DEFINE(sched, , , cpucaps_sleep, cpucaps-sleep);
119 SDT_PROBE_DEFINE(sched, , , cpucaps_wakeup, cpucaps-wakeup);
120 SDT_PROBE_DEFINE(sched, , , schedctl_nopreempt, schedctl-nopreempt);
121 SDT_PROBE_DEFINE(sched, , , schedctl_preempt, schedctl-preempt);
122 SDT_PROBE_DEFINE(sched, , , schedctl_yield, schedctl-yield);
128 hogticks = (hz / 10) * 2; /* Default only. */
133 * General sleep call. Suspends the current thread until a wakeup is
134 * performed on the specified identifier. The thread will then be made
135 * runnable with the specified priority. Sleeps at most timo/hz seconds
136 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
137 * before and after sleeping, else signals are not checked. Returns 0 if
138 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
139 * signal needs to be delivered, ERESTART is returned if the current system
140 * call should be restarted if possible, and EINTR is returned if the system
141 * call should be interrupted by the signal (return EINTR).
143 * The lock argument is unlocked before the caller is suspended, and
144 * re-locked before _sleep() returns. If priority includes the PDROP
145 * flag the lock is not re-locked before returning.
148 _sleep(void *ident, struct lock_object *lock, int priority,
149 const char *wmesg, int timo)
153 struct lock_class *class;
154 int catch, flags, lock_state, pri, rval;
155 WITNESS_SAVE_DECL(lock_witness);
160 if (KTRPOINT(td, KTR_CSW))
163 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
164 "Sleeping on \"%s\"", wmesg);
165 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL,
166 ("sleeping without a lock"));
167 KASSERT(p != NULL, ("msleep1"));
168 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
169 if (priority & PDROP)
170 KASSERT(lock != NULL && lock != &Giant.lock_object,
171 ("PDROP requires a non-Giant lock"));
173 class = LOCK_CLASS(lock);
177 if (cold || SCHEDULER_STOPPED()) {
179 * During autoconfiguration, just return;
180 * don't run any other threads or panic below,
181 * in case this is the idle thread and already asleep.
182 * XXX: this used to do "s = splhigh(); splx(safepri);
183 * splx(s);" to give interrupts a chance, but there is
184 * no way to give interrupts a chance now.
186 if (lock != NULL && priority & PDROP)
187 class->lc_unlock(lock);
190 catch = priority & PCATCH;
191 pri = priority & PRIMASK;
194 * If we are already on a sleep queue, then remove us from that
195 * sleep queue first. We have to do this to handle recursive
198 if (TD_ON_SLEEPQ(td))
199 sleepq_remove(td, td->td_wchan);
201 if (ident == &pause_wchan)
202 flags = SLEEPQ_PAUSE;
204 flags = SLEEPQ_SLEEP;
206 flags |= SLEEPQ_INTERRUPTIBLE;
207 if (priority & PBDRY)
208 flags |= SLEEPQ_STOP_ON_BDRY;
211 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
212 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
214 if (lock == &Giant.lock_object)
215 mtx_assert(&Giant, MA_OWNED);
217 if (lock != NULL && lock != &Giant.lock_object &&
218 !(class->lc_flags & LC_SLEEPABLE)) {
219 WITNESS_SAVE(lock, lock_witness);
220 lock_state = class->lc_unlock(lock);
222 /* GCC needs to follow the Yellow Brick Road */
226 * We put ourselves on the sleep queue and start our timeout
227 * before calling thread_suspend_check, as we could stop there,
228 * and a wakeup or a SIGCONT (or both) could occur while we were
229 * stopped without resuming us. Thus, we must be ready for sleep
230 * when cursig() is called. If the wakeup happens while we're
231 * stopped, then td will no longer be on a sleep queue upon
232 * return from cursig().
234 sleepq_add(ident, lock, wmesg, flags, 0);
236 sleepq_set_timeout(ident, timo);
237 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
238 sleepq_release(ident);
239 WITNESS_SAVE(lock, lock_witness);
240 lock_state = class->lc_unlock(lock);
244 rval = sleepq_timedwait_sig(ident, pri);
246 rval = sleepq_timedwait(ident, pri);
248 rval = sleepq_wait_sig(ident, pri);
250 sleepq_wait(ident, pri);
254 if (KTRPOINT(td, KTR_CSW))
258 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
259 class->lc_lock(lock, lock_state);
260 WITNESS_RESTORE(lock, lock_witness);
266 msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo)
271 WITNESS_SAVE_DECL(mtx);
275 KASSERT(mtx != NULL, ("sleeping without a mutex"));
276 KASSERT(p != NULL, ("msleep1"));
277 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
279 if (cold || SCHEDULER_STOPPED()) {
281 * During autoconfiguration, just return;
282 * don't run any other threads or panic below,
283 * in case this is the idle thread and already asleep.
284 * XXX: this used to do "s = splhigh(); splx(safepri);
285 * splx(s);" to give interrupts a chance, but there is
286 * no way to give interrupts a chance now.
292 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
293 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
296 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
297 WITNESS_SAVE(&mtx->lock_object, mtx);
298 mtx_unlock_spin(mtx);
301 * We put ourselves on the sleep queue and start our timeout.
303 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
305 sleepq_set_timeout(ident, timo);
308 * Can't call ktrace with any spin locks held so it can lock the
309 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
310 * any spin lock. Thus, we have to drop the sleepq spin lock while
311 * we handle those requests. This is safe since we have placed our
312 * thread on the sleep queue already.
315 if (KTRPOINT(td, KTR_CSW)) {
316 sleepq_release(ident);
322 sleepq_release(ident);
323 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
328 rval = sleepq_timedwait(ident, 0);
330 sleepq_wait(ident, 0);
334 if (KTRPOINT(td, KTR_CSW))
339 WITNESS_RESTORE(&mtx->lock_object, mtx);
344 * pause() is like tsleep() except that the intention is to not be
345 * explicitly woken up by another thread. Instead, the current thread
346 * simply wishes to sleep until the timeout expires. It is
347 * implemented using a dummy wait channel.
350 pause(const char *wmesg, int timo)
353 KASSERT(timo != 0, ("pause: timeout required"));
354 return (tsleep(&pause_wchan, 0, wmesg, timo));
358 * Make all threads sleeping on the specified identifier runnable.
366 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
367 sleepq_release(ident);
368 if (wakeup_swapper) {
369 KASSERT(ident != &proc0,
370 ("wakeup and wakeup_swapper and proc0"));
376 * Make a thread sleeping on the specified identifier runnable.
377 * May wake more than one thread if a target thread is currently
381 wakeup_one(void *ident)
386 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
387 sleepq_release(ident);
395 thread_unlock(curthread);
398 panic("%s: did not reenter debugger", __func__);
402 * The machine independent parts of context switching.
405 mi_switch(int flags, struct thread *newtd)
407 uint64_t runtime, new_switchtime;
411 td = curthread; /* XXX */
412 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
413 p = td->td_proc; /* XXX */
414 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
416 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
417 mtx_assert(&Giant, MA_NOTOWNED);
419 KASSERT(td->td_critnest == 1 || panicstr,
420 ("mi_switch: switch in a critical section"));
421 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
422 ("mi_switch: switch must be voluntary or involuntary"));
423 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
426 * Don't perform context switches from the debugger.
430 if (SCHEDULER_STOPPED())
433 td->td_ru.ru_nvcsw++;
435 td->td_ru.ru_nivcsw++;
437 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
440 * Compute the amount of time during which the current
441 * thread was running, and add that to its total so far.
443 new_switchtime = cpu_ticks();
444 runtime = new_switchtime - PCPU_GET(switchtime);
445 td->td_runtime += runtime;
446 td->td_incruntime += runtime;
447 PCPU_SET(switchtime, new_switchtime);
448 td->td_generation++; /* bump preempt-detect counter */
449 PCPU_INC(cnt.v_swtch);
450 PCPU_SET(switchticks, ticks);
451 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
452 td->td_tid, td->td_sched, p->p_pid, td->td_name);
453 #if (KTR_COMPILE & KTR_SCHED) != 0
454 if (TD_IS_IDLETHREAD(td))
455 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
456 "prio:%d", td->td_priority);
458 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
459 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
460 "lockname:\"%s\"", td->td_lockname);
462 SDT_PROBE0(sched, , , preempt);
466 sched_switch(td, newtd, flags);
467 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
468 "prio:%d", td->td_priority);
470 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
471 td->td_tid, td->td_sched, p->p_pid, td->td_name);
474 * If the last thread was exiting, finish cleaning it up.
476 if ((td = PCPU_GET(deadthread))) {
477 PCPU_SET(deadthread, NULL);
483 * Change thread state to be runnable, placing it on the run queue if
484 * it is in memory. If it is swapped out, return true so our caller
485 * will know to awaken the swapper.
488 setrunnable(struct thread *td)
491 THREAD_LOCK_ASSERT(td, MA_OWNED);
492 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
493 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
494 switch (td->td_state) {
500 * If we are only inhibited because we are swapped out
501 * then arange to swap in this process. Otherwise just return.
503 if (td->td_inhibitors != TDI_SWAPPED)
509 printf("state is 0x%x", td->td_state);
510 panic("setrunnable(2)");
512 if ((td->td_flags & TDF_INMEM) == 0) {
513 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
514 td->td_flags |= TDF_SWAPINREQ;
523 * Compute a tenex style load average of a quantity on
524 * 1, 5 and 15 minute intervals.
535 for (i = 0; i < 3; i++)
536 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
537 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
540 * Schedule the next update to occur after 5 seconds, but add a
541 * random variation to avoid synchronisation with processes that
542 * run at regular intervals.
544 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
550 synch_setup(void *dummy)
552 callout_init(&loadav_callout, CALLOUT_MPSAFE);
554 /* Kick off timeout driven events by calling first time. */
562 return (ticks - PCPU_GET(switchticks) >= hogticks);
570 kern_yield(PRI_USER);
581 if (prio == PRI_USER)
582 prio = td->td_user_pri;
584 sched_prio(td, prio);
585 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
591 * General purpose yield system call.
594 yield(struct thread *td, struct yield_args *uap)
598 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
599 sched_prio(td, PRI_MAX_TIMESHARE);
600 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
602 td->td_retval[0] = 0;