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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>
70 #include <vm/vm_param.h>
74 static void synch_setup(void *dummy);
75 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
79 static int pause_wchan;
81 static struct callout loadav_callout;
83 struct loadavg averunnable =
84 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
86 * Constants for averages over 1, 5, and 15 minutes
87 * when sampling at 5 second intervals.
89 static fixpt_t cexp[3] = {
90 0.9200444146293232 * FSCALE, /* exp(-1/12) */
91 0.9834714538216174 * FSCALE, /* exp(-1/60) */
92 0.9944598480048967 * FSCALE, /* exp(-1/180) */
95 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
96 static int fscale __unused = FSCALE;
97 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
99 static void loadav(void *arg);
105 hogticks = (hz / 10) * 2; /* Default only. */
110 * General sleep call. Suspends the current thread until a wakeup is
111 * performed on the specified identifier. The thread will then be made
112 * runnable with the specified priority. Sleeps at most timo/hz seconds
113 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
114 * before and after sleeping, else signals are not checked. Returns 0 if
115 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
116 * signal needs to be delivered, ERESTART is returned if the current system
117 * call should be restarted if possible, and EINTR is returned if the system
118 * call should be interrupted by the signal (return EINTR).
120 * The lock argument is unlocked before the caller is suspended, and
121 * re-locked before _sleep() returns. If priority includes the PDROP
122 * flag the lock is not re-locked before returning.
125 _sleep(void *ident, struct lock_object *lock, int priority,
126 const char *wmesg, int timo)
130 struct lock_class *class;
131 int catch, flags, lock_state, pri, rval;
132 WITNESS_SAVE_DECL(lock_witness);
137 if (KTRPOINT(td, KTR_CSW))
140 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
141 "Sleeping on \"%s\"", wmesg);
142 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL,
143 ("sleeping without a lock"));
144 KASSERT(p != NULL, ("msleep1"));
145 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
146 if (priority & PDROP)
147 KASSERT(lock != NULL && lock != &Giant.lock_object,
148 ("PDROP requires a non-Giant lock"));
150 class = LOCK_CLASS(lock);
156 * During autoconfiguration, just return;
157 * don't run any other threads or panic below,
158 * in case this is the idle thread and already asleep.
159 * XXX: this used to do "s = splhigh(); splx(safepri);
160 * splx(s);" to give interrupts a chance, but there is
161 * no way to give interrupts a chance now.
163 if (lock != NULL && priority & PDROP)
164 class->lc_unlock(lock);
167 catch = priority & PCATCH;
168 pri = priority & PRIMASK;
172 * If we are already on a sleep queue, then remove us from that
173 * sleep queue first. We have to do this to handle recursive
176 if (TD_ON_SLEEPQ(td))
177 sleepq_remove(td, td->td_wchan);
179 if (ident == &pause_wchan)
180 flags = SLEEPQ_PAUSE;
182 flags = SLEEPQ_SLEEP;
184 flags |= SLEEPQ_INTERRUPTIBLE;
187 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
188 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
190 if (lock == &Giant.lock_object)
191 mtx_assert(&Giant, MA_OWNED);
193 if (lock != NULL && lock != &Giant.lock_object &&
194 !(class->lc_flags & LC_SLEEPABLE)) {
195 WITNESS_SAVE(lock, lock_witness);
196 lock_state = class->lc_unlock(lock);
198 /* GCC needs to follow the Yellow Brick Road */
202 * We put ourselves on the sleep queue and start our timeout
203 * before calling thread_suspend_check, as we could stop there,
204 * and a wakeup or a SIGCONT (or both) could occur while we were
205 * stopped without resuming us. Thus, we must be ready for sleep
206 * when cursig() is called. If the wakeup happens while we're
207 * stopped, then td will no longer be on a sleep queue upon
208 * return from cursig().
210 sleepq_add(ident, lock, wmesg, flags, 0);
212 sleepq_set_timeout(ident, timo);
213 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
214 sleepq_release(ident);
215 WITNESS_SAVE(lock, lock_witness);
216 lock_state = class->lc_unlock(lock);
220 rval = sleepq_timedwait_sig(ident, pri);
222 rval = sleepq_timedwait(ident, pri);
224 rval = sleepq_wait_sig(ident, pri);
226 sleepq_wait(ident, pri);
230 if (KTRPOINT(td, KTR_CSW))
234 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
235 class->lc_lock(lock, lock_state);
236 WITNESS_RESTORE(lock, lock_witness);
242 msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo)
247 WITNESS_SAVE_DECL(mtx);
251 KASSERT(mtx != NULL, ("sleeping without a mutex"));
252 KASSERT(p != NULL, ("msleep1"));
253 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
257 * During autoconfiguration, just return;
258 * don't run any other threads or panic below,
259 * in case this is the idle thread and already asleep.
260 * XXX: this used to do "s = splhigh(); splx(safepri);
261 * splx(s);" to give interrupts a chance, but there is
262 * no way to give interrupts a chance now.
268 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
269 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
272 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
273 WITNESS_SAVE(&mtx->lock_object, mtx);
274 mtx_unlock_spin(mtx);
277 * We put ourselves on the sleep queue and start our timeout.
279 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
281 sleepq_set_timeout(ident, timo);
284 * Can't call ktrace with any spin locks held so it can lock the
285 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
286 * any spin lock. Thus, we have to drop the sleepq spin lock while
287 * we handle those requests. This is safe since we have placed our
288 * thread on the sleep queue already.
291 if (KTRPOINT(td, KTR_CSW)) {
292 sleepq_release(ident);
298 sleepq_release(ident);
299 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
304 rval = sleepq_timedwait(ident, 0);
306 sleepq_wait(ident, 0);
310 if (KTRPOINT(td, KTR_CSW))
315 WITNESS_RESTORE(&mtx->lock_object, mtx);
320 * pause() is like tsleep() except that the intention is to not be
321 * explicitly woken up by another thread. Instead, the current thread
322 * simply wishes to sleep until the timeout expires. It is
323 * implemented using a dummy wait channel.
326 pause(const char *wmesg, int timo)
329 KASSERT(timo != 0, ("pause: timeout required"));
330 return (tsleep(&pause_wchan, 0, wmesg, timo));
334 * Make all threads sleeping on the specified identifier runnable.
342 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
343 sleepq_release(ident);
349 * Make a thread sleeping on the specified identifier runnable.
350 * May wake more than one thread if a target thread is currently
354 wakeup_one(void *ident)
359 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
360 sleepq_release(ident);
368 thread_unlock(curthread);
371 panic("%s: did not reenter debugger", __func__);
375 * The machine independent parts of context switching.
378 mi_switch(int flags, struct thread *newtd)
380 uint64_t runtime, new_switchtime;
384 td = curthread; /* XXX */
385 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
386 p = td->td_proc; /* XXX */
387 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
389 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
390 mtx_assert(&Giant, MA_NOTOWNED);
392 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
393 (td->td_owepreempt) && (flags & SW_INVOL) != 0 &&
394 newtd == NULL) || panicstr,
395 ("mi_switch: switch in a critical section"));
396 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
397 ("mi_switch: switch must be voluntary or involuntary"));
398 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
401 * Don't perform context switches from the debugger.
406 td->td_ru.ru_nvcsw++;
408 td->td_ru.ru_nivcsw++;
410 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
413 * Compute the amount of time during which the current
414 * thread was running, and add that to its total so far.
416 new_switchtime = cpu_ticks();
417 runtime = new_switchtime - PCPU_GET(switchtime);
418 td->td_runtime += runtime;
419 td->td_incruntime += runtime;
420 PCPU_SET(switchtime, new_switchtime);
421 td->td_generation++; /* bump preempt-detect counter */
422 PCPU_INC(cnt.v_swtch);
423 PCPU_SET(switchticks, ticks);
424 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
425 td->td_tid, td->td_sched, p->p_pid, td->td_name);
426 #if (KTR_COMPILE & KTR_SCHED) != 0
427 if (TD_IS_IDLETHREAD(td))
428 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
429 td, td->td_name, td->td_priority);
430 else if (newtd != NULL)
432 "mi_switch: %p(%s) prio %d preempted by %p(%s)",
433 td, td->td_name, td->td_priority, newtd,
437 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
438 td, td->td_name, td->td_priority,
439 td->td_inhibitors, td->td_wmesg, td->td_lockname);
444 sched_switch(td, newtd, flags);
445 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
446 td, td->td_name, td->td_priority);
448 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
449 td->td_tid, td->td_sched, p->p_pid, td->td_name);
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.
513 for (i = 0; i < 3; i++)
514 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
515 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
518 * Schedule the next update to occur after 5 seconds, but add a
519 * random variation to avoid synchronisation with processes that
520 * run at regular intervals.
522 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
528 synch_setup(void *dummy)
530 callout_init(&loadav_callout, CALLOUT_MPSAFE);
532 /* Kick off timeout driven events by calling first time. */
537 * General purpose yield system call.
540 yield(struct thread *td, struct yield_args *uap)
544 sched_prio(td, PRI_MAX_TIMESHARE);
545 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
547 td->td_retval[0] = 0;