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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"
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/condvar.h>
46 #include <sys/kernel.h>
49 #include <sys/mutex.h>
51 #include <sys/resourcevar.h>
52 #include <sys/sched.h>
53 #include <sys/signalvar.h>
54 #include <sys/sleepqueue.h>
57 #include <sys/sysctl.h>
58 #include <sys/sysproto.h>
59 #include <sys/vmmeter.h>
62 #include <sys/ktrace.h>
65 #include <machine/cpu.h>
67 static void synch_setup(void *dummy);
68 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL)
73 static struct callout loadav_callout;
74 static struct callout lbolt_callout;
76 struct loadavg averunnable =
77 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
79 * Constants for averages over 1, 5, and 15 minutes
80 * when sampling at 5 second intervals.
82 static fixpt_t cexp[3] = {
83 0.9200444146293232 * FSCALE, /* exp(-1/12) */
84 0.9834714538216174 * FSCALE, /* exp(-1/60) */
85 0.9944598480048967 * FSCALE, /* exp(-1/180) */
88 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
89 static int fscale __unused = FSCALE;
90 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
92 static void loadav(void *arg);
93 static void lboltcb(void *arg);
99 hogticks = (hz / 10) * 2; /* Default only. */
104 * General sleep call. Suspends the current thread until a wakeup is
105 * performed on the specified identifier. The thread will then be made
106 * runnable with the specified priority. Sleeps at most timo/hz seconds
107 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
108 * before and after sleeping, else signals are not checked. Returns 0 if
109 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
110 * signal needs to be delivered, ERESTART is returned if the current system
111 * call should be restarted if possible, and EINTR is returned if the system
112 * call should be interrupted by the signal (return EINTR).
114 * The mutex argument is unlocked before the caller is suspended, and
115 * re-locked before msleep returns. If priority includes the PDROP
116 * flag the mutex is not re-locked before returning.
119 msleep(ident, mtx, priority, wmesg, timo)
127 int catch, rval, flags;
128 WITNESS_SAVE_DECL(mtx);
133 if (KTRPOINT(td, KTR_CSW))
136 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, mtx == NULL ? NULL :
137 &mtx->mtx_object, "Sleeping on \"%s\"", wmesg);
138 KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL,
139 ("sleeping without a mutex"));
140 KASSERT(p != NULL, ("msleep1"));
141 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
145 * During autoconfiguration, just return;
146 * don't run any other threads or panic below,
147 * in case this is the idle thread and already asleep.
148 * XXX: this used to do "s = splhigh(); splx(safepri);
149 * splx(s);" to give interrupts a chance, but there is
150 * no way to give interrupts a chance now.
152 if (mtx != NULL && priority & PDROP)
156 catch = priority & PCATCH;
160 * If we are already on a sleep queue, then remove us from that
161 * sleep queue first. We have to do this to handle recursive
164 if (TD_ON_SLEEPQ(td))
165 sleepq_remove(td, td->td_wchan);
167 flags = SLEEPQ_MSLEEP;
169 flags |= SLEEPQ_INTERRUPTIBLE;
172 CTR5(KTR_PROC, "msleep: thread %p (pid %ld, %s) on %s (%p)",
173 (void *)td, (long)p->p_pid, p->p_comm, wmesg, ident);
177 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
178 WITNESS_SAVE(&mtx->mtx_object, mtx);
183 * We put ourselves on the sleep queue and start our timeout
184 * before calling thread_suspend_check, as we could stop there,
185 * and a wakeup or a SIGCONT (or both) could occur while we were
186 * stopped without resuming us. Thus, we must be ready for sleep
187 * when cursig() is called. If the wakeup happens while we're
188 * stopped, then td will no longer be on a sleep queue upon
189 * return from cursig().
191 sleepq_add(ident, mtx, wmesg, flags);
193 sleepq_set_timeout(ident, timo);
196 * Adjust this thread's priority.
198 mtx_lock_spin(&sched_lock);
199 sched_prio(td, priority & PRIMASK);
200 mtx_unlock_spin(&sched_lock);
203 rval = sleepq_timedwait_sig(ident);
205 rval = sleepq_timedwait(ident);
207 rval = sleepq_wait_sig(ident);
213 if (KTRPOINT(td, KTR_CSW))
217 if (mtx != NULL && !(priority & PDROP)) {
219 WITNESS_RESTORE(&mtx->mtx_object, mtx);
225 msleep_spin(ident, mtx, wmesg, timo)
234 WITNESS_SAVE_DECL(mtx);
238 KASSERT(mtx != NULL, ("sleeping without a mutex"));
239 KASSERT(p != NULL, ("msleep1"));
240 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
244 * During autoconfiguration, just return;
245 * don't run any other threads or panic below,
246 * in case this is the idle thread and already asleep.
247 * XXX: this used to do "s = splhigh(); splx(safepri);
248 * splx(s);" to give interrupts a chance, but there is
249 * no way to give interrupts a chance now.
255 CTR5(KTR_PROC, "msleep_spin: thread %p (pid %ld, %s) on %s (%p)",
256 (void *)td, (long)p->p_pid, p->p_comm, wmesg, ident);
259 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
260 WITNESS_SAVE(&mtx->mtx_object, mtx);
261 mtx_unlock_spin(mtx);
264 * We put ourselves on the sleep queue and start our timeout.
266 sleepq_add(ident, mtx, wmesg, SLEEPQ_MSLEEP);
268 sleepq_set_timeout(ident, timo);
271 * Can't call ktrace with any spin locks held so it can lock the
272 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
273 * any spin lock. Thus, we have to drop the sleepq spin lock while
274 * we handle those requests. This is safe since we have placed our
275 * thread on the sleep queue already.
278 if (KTRPOINT(td, KTR_CSW)) {
279 sleepq_release(ident);
285 sleepq_release(ident);
286 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
291 rval = sleepq_timedwait(ident);
297 if (KTRPOINT(td, KTR_CSW))
302 WITNESS_RESTORE(&mtx->mtx_object, mtx);
307 * Make all threads sleeping on the specified identifier runnable.
311 register void *ident;
315 sleepq_broadcast(ident, SLEEPQ_MSLEEP, -1);
319 * Make a thread sleeping on the specified identifier runnable.
320 * May wake more than one thread if a target thread is currently
325 register void *ident;
329 sleepq_signal(ident, SLEEPQ_MSLEEP, -1);
333 * The machine independent parts of context switching.
336 mi_switch(int flags, struct thread *newtd)
338 uint64_t new_switchtime;
342 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
343 td = curthread; /* XXX */
344 p = td->td_proc; /* XXX */
345 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
347 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
348 mtx_assert(&Giant, MA_NOTOWNED);
350 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
351 (td->td_owepreempt) && (flags & SW_INVOL) != 0 &&
352 newtd == NULL) || panicstr,
353 ("mi_switch: switch in a critical section"));
354 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
355 ("mi_switch: switch must be voluntary or involuntary"));
356 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
359 p->p_stats->p_ru.ru_nvcsw++;
361 p->p_stats->p_ru.ru_nivcsw++;
364 * Compute the amount of time during which the current
365 * process was running, and add that to its total so far.
367 new_switchtime = cpu_ticks();
368 p->p_rux.rux_runtime += (new_switchtime - PCPU_GET(switchtime));
369 p->p_rux.rux_uticks += td->td_uticks;
371 p->p_rux.rux_iticks += td->td_iticks;
373 p->p_rux.rux_sticks += td->td_sticks;
376 td->td_generation++; /* bump preempt-detect counter */
379 * Don't perform context switches from the debugger.
382 mtx_unlock_spin(&sched_lock);
385 panic("%s: did not reenter debugger", __func__);
389 * Check if the process exceeds its cpu resource allocation. If
390 * it reaches the max, arrange to kill the process in ast().
392 if (p->p_cpulimit != RLIM_INFINITY &&
393 p->p_rux.rux_runtime >= p->p_cpulimit * cpu_tickrate()) {
394 p->p_sflag |= PS_XCPU;
395 td->td_flags |= TDF_ASTPENDING;
399 * Finish up stats for outgoing thread.
402 PCPU_SET(switchtime, new_switchtime);
403 PCPU_SET(switchticks, ticks);
404 CTR4(KTR_PROC, "mi_switch: old thread %p (kse %p, pid %ld, %s)",
405 (void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
406 if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
407 newtd = thread_switchout(td, flags, newtd);
408 #if (KTR_COMPILE & KTR_SCHED) != 0
409 if (td == PCPU_GET(idlethread))
410 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
411 td, td->td_proc->p_comm, td->td_priority);
412 else if (newtd != NULL)
414 "mi_switch: %p(%s) prio %d preempted by %p(%s)",
415 td, td->td_proc->p_comm, td->td_priority, newtd,
416 newtd->td_proc->p_comm);
419 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
420 td, td->td_proc->p_comm, td->td_priority,
421 td->td_inhibitors, td->td_wmesg, td->td_lockname);
423 sched_switch(td, newtd, flags);
424 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
425 td, td->td_proc->p_comm, td->td_priority);
427 CTR4(KTR_PROC, "mi_switch: new thread %p (kse %p, pid %ld, %s)",
428 (void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
431 * If the last thread was exiting, finish cleaning it up.
433 if ((td = PCPU_GET(deadthread))) {
434 PCPU_SET(deadthread, NULL);
440 * Change process state to be runnable,
441 * placing it on the run queue if it is in memory,
442 * and awakening the swapper if it isn't in memory.
445 setrunnable(struct thread *td)
450 mtx_assert(&sched_lock, MA_OWNED);
451 switch (p->p_state) {
453 panic("setrunnable(1)");
457 switch (td->td_state) {
463 * If we are only inhibited because we are swapped out
464 * then arange to swap in this process. Otherwise just return.
466 if (td->td_inhibitors != TDI_SWAPPED)
468 /* XXX: intentional fall-through ? */
472 printf("state is 0x%x", td->td_state);
473 panic("setrunnable(2)");
475 if ((p->p_sflag & PS_INMEM) == 0) {
476 if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
477 p->p_sflag |= PS_SWAPINREQ;
479 * due to a LOR between sched_lock and
480 * the sleepqueue chain locks, use
481 * lower level scheduling functions.
490 * Compute a tenex style load average of a quantity on
491 * 1, 5 and 15 minute intervals.
492 * XXXKSE Needs complete rewrite when correct info is available.
493 * Completely Bogus.. only works with 1:1 (but compiles ok now :-)
504 for (i = 0; i < 3; i++)
505 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
506 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
509 * Schedule the next update to occur after 5 seconds, but add a
510 * random variation to avoid synchronisation with processes that
511 * run at regular intervals.
513 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
521 callout_reset(&lbolt_callout, hz, lboltcb, NULL);
529 callout_init(&loadav_callout, CALLOUT_MPSAFE);
530 callout_init(&lbolt_callout, CALLOUT_MPSAFE);
532 /* Kick off timeout driven events by calling first time. */
538 * General purpose yield system call
541 yield(struct thread *td, struct yield_args *uap)
546 mtx_assert(&Giant, MA_NOTOWNED);
547 mtx_lock_spin(&sched_lock);
548 sched_prio(td, PRI_MAX_TIMESHARE);
549 mi_switch(SW_VOL, NULL);
550 mtx_unlock_spin(&sched_lock);
551 td->td_retval[0] = 0;