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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,
73 static int pause_wchan;
75 static struct callout loadav_callout;
76 static struct callout lbolt_callout;
78 struct loadavg averunnable =
79 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
81 * Constants for averages over 1, 5, and 15 minutes
82 * when sampling at 5 second intervals.
84 static fixpt_t cexp[3] = {
85 0.9200444146293232 * FSCALE, /* exp(-1/12) */
86 0.9834714538216174 * FSCALE, /* exp(-1/60) */
87 0.9944598480048967 * FSCALE, /* exp(-1/180) */
90 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
91 static int fscale __unused = FSCALE;
92 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
94 static void loadav(void *arg);
95 static void lboltcb(void *arg);
101 hogticks = (hz / 10) * 2; /* Default only. */
106 * General sleep call. Suspends the current thread until a wakeup is
107 * performed on the specified identifier. The thread will then be made
108 * runnable with the specified priority. Sleeps at most timo/hz seconds
109 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
110 * before and after sleeping, else signals are not checked. Returns 0 if
111 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
112 * signal needs to be delivered, ERESTART is returned if the current system
113 * call should be restarted if possible, and EINTR is returned if the system
114 * call should be interrupted by the signal (return EINTR).
116 * The lock argument is unlocked before the caller is suspended, and
117 * re-locked before _sleep() returns. If priority includes the PDROP
118 * flag the lock is not re-locked before returning.
121 _sleep(void *ident, struct lock_object *lock, int priority,
122 const char *wmesg, int timo)
126 struct lock_class *class;
127 int catch, flags, lock_state, pri, rval;
128 WITNESS_SAVE_DECL(lock_witness);
133 if (KTRPOINT(td, KTR_CSW))
136 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
137 "Sleeping on \"%s\"", wmesg);
138 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL ||
139 ident == &lbolt, ("sleeping without a lock"));
140 KASSERT(p != NULL, ("msleep1"));
141 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
142 if (priority & PDROP)
143 KASSERT(lock != NULL && lock != &Giant.lock_object,
144 ("PDROP requires a non-Giant lock"));
146 class = LOCK_CLASS(lock);
152 * During autoconfiguration, just return;
153 * don't run any other threads or panic below,
154 * in case this is the idle thread and already asleep.
155 * XXX: this used to do "s = splhigh(); splx(safepri);
156 * splx(s);" to give interrupts a chance, but there is
157 * no way to give interrupts a chance now.
159 if (lock != NULL && priority & PDROP)
160 class->lc_unlock(lock);
163 catch = priority & PCATCH;
167 * If we are already on a sleep queue, then remove us from that
168 * sleep queue first. We have to do this to handle recursive
171 if (TD_ON_SLEEPQ(td))
172 sleepq_remove(td, td->td_wchan);
174 if (ident == &pause_wchan)
175 flags = SLEEPQ_PAUSE;
177 flags = SLEEPQ_SLEEP;
179 flags |= SLEEPQ_INTERRUPTIBLE;
182 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
183 td->td_tid, p->p_pid, p->p_comm, wmesg, ident);
186 if (lock != NULL && lock != &Giant.lock_object &&
187 !(class->lc_flags & LC_SLEEPABLE)) {
188 WITNESS_SAVE(lock, lock_witness);
189 lock_state = class->lc_unlock(lock);
191 /* GCC needs to follow the Yellow Brick Road */
195 * We put ourselves on the sleep queue and start our timeout
196 * before calling thread_suspend_check, as we could stop there,
197 * and a wakeup or a SIGCONT (or both) could occur while we were
198 * stopped without resuming us. Thus, we must be ready for sleep
199 * when cursig() is called. If the wakeup happens while we're
200 * stopped, then td will no longer be on a sleep queue upon
201 * return from cursig().
203 sleepq_add(ident, ident == &lbolt ? NULL : lock, wmesg, flags, 0);
205 sleepq_set_timeout(ident, timo);
206 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
207 sleepq_release(ident);
208 WITNESS_SAVE(lock, lock_witness);
209 lock_state = class->lc_unlock(lock);
214 * Adjust this thread's priority, if necessary.
216 pri = priority & PRIMASK;
217 if (pri != 0 && pri != td->td_priority) {
224 rval = sleepq_timedwait_sig(ident);
226 rval = sleepq_timedwait(ident);
228 rval = sleepq_wait_sig(ident);
234 if (KTRPOINT(td, KTR_CSW))
238 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
239 class->lc_lock(lock, lock_state);
240 WITNESS_RESTORE(lock, lock_witness);
246 msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo)
251 WITNESS_SAVE_DECL(mtx);
255 KASSERT(mtx != NULL, ("sleeping without a mutex"));
256 KASSERT(p != NULL, ("msleep1"));
257 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
261 * During autoconfiguration, just return;
262 * don't run any other threads or panic below,
263 * in case this is the idle thread and already asleep.
264 * XXX: this used to do "s = splhigh(); splx(safepri);
265 * splx(s);" to give interrupts a chance, but there is
266 * no way to give interrupts a chance now.
272 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
273 td->td_tid, p->p_pid, p->p_comm, wmesg, ident);
276 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
277 WITNESS_SAVE(&mtx->lock_object, mtx);
278 mtx_unlock_spin(mtx);
281 * We put ourselves on the sleep queue and start our timeout.
283 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
285 sleepq_set_timeout(ident, timo);
288 * Can't call ktrace with any spin locks held so it can lock the
289 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
290 * any spin lock. Thus, we have to drop the sleepq spin lock while
291 * we handle those requests. This is safe since we have placed our
292 * thread on the sleep queue already.
295 if (KTRPOINT(td, KTR_CSW)) {
296 sleepq_release(ident);
302 sleepq_release(ident);
303 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
308 rval = sleepq_timedwait(ident);
314 if (KTRPOINT(td, KTR_CSW))
319 WITNESS_RESTORE(&mtx->lock_object, mtx);
324 * pause() is like tsleep() except that the intention is to not be
325 * explicitly woken up by another thread. Instead, the current thread
326 * simply wishes to sleep until the timeout expires. It is
327 * implemented using a dummy wait channel.
330 pause(const char *wmesg, int timo)
333 KASSERT(timo != 0, ("pause: timeout required"));
334 return (tsleep(&pause_wchan, 0, wmesg, timo));
338 * Make all threads sleeping on the specified identifier runnable.
346 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, -1, 0);
352 * Make a thread sleeping on the specified identifier runnable.
353 * May wake more than one thread if a target thread is currently
357 wakeup_one(void *ident)
362 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, -1, 0);
363 sleepq_release(ident);
369 * The machine independent parts of context switching.
372 mi_switch(int flags, struct thread *newtd)
374 uint64_t runtime, new_switchtime;
378 td = curthread; /* XXX */
379 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
380 p = td->td_proc; /* XXX */
381 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
383 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
384 mtx_assert(&Giant, MA_NOTOWNED);
386 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
387 (td->td_owepreempt) && (flags & SW_INVOL) != 0 &&
388 newtd == NULL) || panicstr,
389 ("mi_switch: switch in a critical section"));
390 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
391 ("mi_switch: switch must be voluntary or involuntary"));
392 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
395 * Don't perform context switches from the debugger.
401 panic("%s: did not reenter debugger", __func__);
404 td->td_ru.ru_nvcsw++;
406 td->td_ru.ru_nivcsw++;
408 * Compute the amount of time during which the current
409 * thread was running, and add that to its total so far.
411 new_switchtime = cpu_ticks();
412 runtime = new_switchtime - PCPU_GET(switchtime);
413 td->td_runtime += runtime;
414 td->td_incruntime += runtime;
415 PCPU_SET(switchtime, new_switchtime);
416 td->td_generation++; /* bump preempt-detect counter */
417 PCPU_INC(cnt.v_swtch);
418 PCPU_SET(switchticks, ticks);
419 CTR4(KTR_PROC, "mi_switch: old thread %ld (kse %p, pid %ld, %s)",
420 td->td_tid, td->td_sched, p->p_pid, p->p_comm);
421 #if (KTR_COMPILE & KTR_SCHED) != 0
422 if (TD_IS_IDLETHREAD(td))
423 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
424 td, td->td_proc->p_comm, td->td_priority);
425 else if (newtd != NULL)
427 "mi_switch: %p(%s) prio %d preempted by %p(%s)",
428 td, td->td_proc->p_comm, td->td_priority, newtd,
429 newtd->td_proc->p_comm);
432 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
433 td, td->td_proc->p_comm, td->td_priority,
434 td->td_inhibitors, td->td_wmesg, td->td_lockname);
437 * We call thread_switchout after the KTR_SCHED prints above so kse
438 * selecting a new thread to run does not show up as a preemption.
441 if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
442 newtd = thread_switchout(td, flags, newtd);
444 sched_switch(td, newtd, flags);
445 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
446 td, td->td_proc->p_comm, td->td_priority);
448 CTR4(KTR_PROC, "mi_switch: new thread %ld (kse %p, pid %ld, %s)",
449 td->td_tid, td->td_sched, p->p_pid, p->p_comm);
452 * If the last thread was exiting, finish cleaning it up.
454 if ((td = PCPU_GET(deadthread))) {
455 PCPU_SET(deadthread, NULL);
461 * Change thread state to be runnable, placing it on the run queue if
462 * it is in memory. If it is swapped out, return true so our caller
463 * will know to awaken the swapper.
466 setrunnable(struct thread *td)
469 THREAD_LOCK_ASSERT(td, MA_OWNED);
470 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
471 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
472 switch (td->td_state) {
478 * If we are only inhibited because we are swapped out
479 * then arange to swap in this process. Otherwise just return.
481 if (td->td_inhibitors != TDI_SWAPPED)
487 printf("state is 0x%x", td->td_state);
488 panic("setrunnable(2)");
490 if ((td->td_flags & TDF_INMEM) == 0) {
491 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
492 td->td_flags |= TDF_SWAPINREQ;
501 * Compute a tenex style load average of a quantity on
502 * 1, 5 and 15 minute intervals.
503 * XXXKSE Needs complete rewrite when correct info is available.
504 * Completely Bogus.. only works with 1:1 (but compiles ok now :-)
515 for (i = 0; i < 3; i++)
516 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
517 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
520 * Schedule the next update to occur after 5 seconds, but add a
521 * random variation to avoid synchronisation with processes that
522 * run at regular intervals.
524 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
532 callout_reset(&lbolt_callout, hz, lboltcb, NULL);
537 synch_setup(void *dummy)
539 callout_init(&loadav_callout, CALLOUT_MPSAFE);
540 callout_init(&lbolt_callout, CALLOUT_MPSAFE);
542 /* Kick off timeout driven events by calling first time. */
548 * General purpose yield system call.
551 yield(struct thread *td, struct yield_args *uap)
555 sched_prio(td, PRI_MAX_TIMESHARE);
556 mi_switch(SW_VOL, NULL);
558 td->td_retval[0] = 0;