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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>
54 #include <sys/signalvar.h>
55 #include <sys/sleepqueue.h>
58 #include <sys/sysctl.h>
59 #include <sys/sysproto.h>
60 #include <sys/vmmeter.h>
63 #include <sys/ktrace.h>
66 #include <machine/cpu.h>
68 static void synch_setup(void *dummy);
69 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
74 static int pause_wchan;
76 static struct callout loadav_callout;
77 static struct callout lbolt_callout;
79 struct loadavg averunnable =
80 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
82 * Constants for averages over 1, 5, and 15 minutes
83 * when sampling at 5 second intervals.
85 static fixpt_t cexp[3] = {
86 0.9200444146293232 * FSCALE, /* exp(-1/12) */
87 0.9834714538216174 * FSCALE, /* exp(-1/60) */
88 0.9944598480048967 * FSCALE, /* exp(-1/180) */
91 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
92 static int fscale __unused = FSCALE;
93 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
95 static void loadav(void *arg);
96 static void lboltcb(void *arg);
102 hogticks = (hz / 10) * 2; /* Default only. */
107 * General sleep call. Suspends the current thread until a wakeup is
108 * performed on the specified identifier. The thread will then be made
109 * runnable with the specified priority. Sleeps at most timo/hz seconds
110 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
111 * before and after sleeping, else signals are not checked. Returns 0 if
112 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
113 * signal needs to be delivered, ERESTART is returned if the current system
114 * call should be restarted if possible, and EINTR is returned if the system
115 * call should be interrupted by the signal (return EINTR).
117 * The lock argument is unlocked before the caller is suspended, and
118 * re-locked before _sleep() returns. If priority includes the PDROP
119 * flag the lock is not re-locked before returning.
122 _sleep(void *ident, struct lock_object *lock, int priority,
123 const char *wmesg, int timo)
127 struct lock_class *class;
128 int catch, flags, lock_state, pri, rval;
129 WITNESS_SAVE_DECL(lock_witness);
134 if (KTRPOINT(td, KTR_CSW))
137 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
138 "Sleeping on \"%s\"", wmesg);
139 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL ||
140 ident == &lbolt, ("sleeping without a lock"));
141 KASSERT(p != NULL, ("msleep1"));
142 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
144 class = LOCK_CLASS(lock);
150 * During autoconfiguration, just return;
151 * don't run any other threads or panic below,
152 * in case this is the idle thread and already asleep.
153 * XXX: this used to do "s = splhigh(); splx(safepri);
154 * splx(s);" to give interrupts a chance, but there is
155 * no way to give interrupts a chance now.
157 if (lock != NULL && priority & PDROP)
158 class->lc_unlock(lock);
161 catch = priority & PCATCH;
162 pri = priority & PRIMASK;
166 * If we are already on a sleep queue, then remove us from that
167 * sleep queue first. We have to do this to handle recursive
170 if (TD_ON_SLEEPQ(td))
171 sleepq_remove(td, td->td_wchan);
173 if (ident == &pause_wchan)
174 flags = SLEEPQ_PAUSE;
176 flags = SLEEPQ_SLEEP;
178 flags |= SLEEPQ_INTERRUPTIBLE;
181 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
182 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
185 if (lock != NULL && !(class->lc_flags & LC_SLEEPABLE)) {
186 WITNESS_SAVE(lock, lock_witness);
187 lock_state = class->lc_unlock(lock);
189 /* GCC needs to follow the Yellow Brick Road */
193 * We put ourselves on the sleep queue and start our timeout
194 * before calling thread_suspend_check, as we could stop there,
195 * and a wakeup or a SIGCONT (or both) could occur while we were
196 * stopped without resuming us. Thus, we must be ready for sleep
197 * when cursig() is called. If the wakeup happens while we're
198 * stopped, then td will no longer be on a sleep queue upon
199 * return from cursig().
201 sleepq_add(ident, ident == &lbolt ? NULL : lock, wmesg, flags, 0);
203 sleepq_set_timeout(ident, timo);
204 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
205 sleepq_release(ident);
206 WITNESS_SAVE(lock, lock_witness);
207 lock_state = class->lc_unlock(lock);
211 rval = sleepq_timedwait_sig(ident, pri);
213 rval = sleepq_timedwait(ident, pri);
215 rval = sleepq_wait_sig(ident, pri);
217 sleepq_wait(ident, pri);
221 if (KTRPOINT(td, KTR_CSW))
225 if (lock != NULL && !(priority & PDROP)) {
226 class->lc_lock(lock, lock_state);
227 WITNESS_RESTORE(lock, lock_witness);
233 msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo)
238 WITNESS_SAVE_DECL(mtx);
242 KASSERT(mtx != NULL, ("sleeping without a mutex"));
243 KASSERT(p != NULL, ("msleep1"));
244 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
248 * During autoconfiguration, just return;
249 * don't run any other threads or panic below,
250 * in case this is the idle thread and already asleep.
251 * XXX: this used to do "s = splhigh(); splx(safepri);
252 * splx(s);" to give interrupts a chance, but there is
253 * no way to give interrupts a chance now.
259 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
260 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
263 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
264 WITNESS_SAVE(&mtx->lock_object, mtx);
265 mtx_unlock_spin(mtx);
268 * We put ourselves on the sleep queue and start our timeout.
270 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
272 sleepq_set_timeout(ident, timo);
275 * Can't call ktrace with any spin locks held so it can lock the
276 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
277 * any spin lock. Thus, we have to drop the sleepq spin lock while
278 * we handle those requests. This is safe since we have placed our
279 * thread on the sleep queue already.
282 if (KTRPOINT(td, KTR_CSW)) {
283 sleepq_release(ident);
289 sleepq_release(ident);
290 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
295 rval = sleepq_timedwait(ident, 0);
297 sleepq_wait(ident, 0);
301 if (KTRPOINT(td, KTR_CSW))
306 WITNESS_RESTORE(&mtx->lock_object, mtx);
311 * pause() is like tsleep() except that the intention is to not be
312 * explicitly woken up by another thread. Instead, the current thread
313 * simply wishes to sleep until the timeout expires. It is
314 * implemented using a dummy wait channel.
317 pause(const char *wmesg, int timo)
320 KASSERT(timo != 0, ("pause: timeout required"));
321 return (tsleep(&pause_wchan, 0, wmesg, timo));
325 * Make all threads sleeping on the specified identifier runnable.
332 sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
333 sleepq_release(ident);
337 * Make a thread sleeping on the specified identifier runnable.
338 * May wake more than one thread if a target thread is currently
342 wakeup_one(void *ident)
346 sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
347 sleepq_release(ident);
353 thread_unlock(curthread);
356 panic("%s: did not reenter debugger", __func__);
360 * The machine independent parts of context switching.
363 mi_switch(int flags, struct thread *newtd)
365 uint64_t runtime, new_switchtime;
369 td = curthread; /* XXX */
370 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
371 p = td->td_proc; /* XXX */
372 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
374 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
375 mtx_assert(&Giant, MA_NOTOWNED);
377 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
378 (td->td_owepreempt) && (flags & SW_INVOL) != 0 &&
379 newtd == NULL) || panicstr,
380 ("mi_switch: switch in a critical section"));
381 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
382 ("mi_switch: switch must be voluntary or involuntary"));
383 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
386 * Don't perform context switches from the debugger.
391 td->td_ru.ru_nvcsw++;
393 td->td_ru.ru_nivcsw++;
395 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
398 * Compute the amount of time during which the current
399 * thread was running, and add that to its total so far.
401 new_switchtime = cpu_ticks();
402 runtime = new_switchtime - PCPU_GET(switchtime);
403 td->td_runtime += runtime;
404 td->td_incruntime += runtime;
405 PCPU_SET(switchtime, new_switchtime);
406 td->td_generation++; /* bump preempt-detect counter */
407 PCPU_INC(cnt.v_swtch);
408 PCPU_SET(switchticks, ticks);
409 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
410 td->td_tid, td->td_sched, p->p_pid, td->td_name);
411 #if (KTR_COMPILE & KTR_SCHED) != 0
412 if (TD_IS_IDLETHREAD(td))
413 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
414 td, td->td_name, td->td_priority);
415 else if (newtd != NULL)
417 "mi_switch: %p(%s) prio %d preempted by %p(%s)",
418 td, td->td_name, td->td_priority, newtd,
422 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
423 td, td->td_name, td->td_priority,
424 td->td_inhibitors, td->td_wmesg, td->td_lockname);
426 sched_switch(td, newtd, flags);
427 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
428 td, td->td_name, td->td_priority);
430 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
431 td->td_tid, td->td_sched, p->p_pid, td->td_name);
434 * If the last thread was exiting, finish cleaning it up.
436 if ((td = PCPU_GET(deadthread))) {
437 PCPU_SET(deadthread, NULL);
443 * Change process state to be runnable,
444 * placing it on the run queue if it is in memory,
445 * and awakening the swapper if it isn't in memory.
448 setrunnable(struct thread *td)
451 THREAD_LOCK_ASSERT(td, MA_OWNED);
452 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
453 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
454 switch (td->td_state) {
460 * If we are only inhibited because we are swapped out
461 * then arange to swap in this process. Otherwise just return.
463 if (td->td_inhibitors != TDI_SWAPPED)
465 /* XXX: intentional fall-through ? */
469 printf("state is 0x%x", td->td_state);
470 panic("setrunnable(2)");
472 if ((td->td_flags & TDF_INMEM) == 0) {
473 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
474 td->td_flags |= TDF_SWAPINREQ;
476 * due to a LOR between the thread lock and
477 * the sleepqueue chain locks, use
478 * lower level scheduling functions.
487 * Compute a tenex style load average of a quantity on
488 * 1, 5 and 15 minute intervals.
499 for (i = 0; i < 3; i++)
500 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
501 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
504 * Schedule the next update to occur after 5 seconds, but add a
505 * random variation to avoid synchronisation with processes that
506 * run at regular intervals.
508 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
516 callout_reset(&lbolt_callout, hz, lboltcb, NULL);
521 synch_setup(void *dummy)
523 callout_init(&loadav_callout, CALLOUT_MPSAFE);
524 callout_init(&lbolt_callout, CALLOUT_MPSAFE);
526 /* Kick off timeout driven events by calling first time. */
532 * General purpose yield system call.
535 yield(struct thread *td, struct yield_args *uap)
539 sched_prio(td, PRI_MAX_TIMESHARE);
540 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
542 td->td_retval[0] = 0;