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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 #define KTDSTATE(td) \
75 (((td)->td_inhibitors & TDI_SLEEPING) != 0 ? "sleep" : \
76 ((td)->td_inhibitors & TDI_SUSPENDED) != 0 ? "suspended" : \
77 ((td)->td_inhibitors & TDI_SWAPPED) != 0 ? "swapped" : \
78 ((td)->td_inhibitors & TDI_LOCK) != 0 ? "blocked" : \
79 ((td)->td_inhibitors & TDI_IWAIT) != 0 ? "iwait" : "yielding")
81 static void synch_setup(void *dummy);
82 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
86 static int pause_wchan;
88 static struct callout loadav_callout;
90 struct loadavg averunnable =
91 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
93 * Constants for averages over 1, 5, and 15 minutes
94 * when sampling at 5 second intervals.
96 static fixpt_t cexp[3] = {
97 0.9200444146293232 * FSCALE, /* exp(-1/12) */
98 0.9834714538216174 * FSCALE, /* exp(-1/60) */
99 0.9944598480048967 * FSCALE, /* exp(-1/180) */
102 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
103 static int fscale __unused = FSCALE;
104 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
106 static void loadav(void *arg);
112 hogticks = (hz / 10) * 2; /* Default only. */
117 * General sleep call. Suspends the current thread until a wakeup is
118 * performed on the specified identifier. The thread will then be made
119 * runnable with the specified priority. Sleeps at most timo/hz seconds
120 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
121 * before and after sleeping, else signals are not checked. Returns 0 if
122 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
123 * signal needs to be delivered, ERESTART is returned if the current system
124 * call should be restarted if possible, and EINTR is returned if the system
125 * call should be interrupted by the signal (return EINTR).
127 * The lock argument is unlocked before the caller is suspended, and
128 * re-locked before _sleep() returns. If priority includes the PDROP
129 * flag the lock is not re-locked before returning.
132 _sleep(void *ident, struct lock_object *lock, int priority,
133 const char *wmesg, int timo)
137 struct lock_class *class;
138 int catch, flags, lock_state, pri, rval;
139 WITNESS_SAVE_DECL(lock_witness);
144 if (KTRPOINT(td, KTR_CSW))
147 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
148 "Sleeping on \"%s\"", wmesg);
149 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL,
150 ("sleeping without a lock"));
151 KASSERT(p != NULL, ("msleep1"));
152 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
153 if (priority & PDROP)
154 KASSERT(lock != NULL && lock != &Giant.lock_object,
155 ("PDROP requires a non-Giant lock"));
157 class = LOCK_CLASS(lock);
163 * During autoconfiguration, just return;
164 * don't run any other threads or panic below,
165 * in case this is the idle thread and already asleep.
166 * XXX: this used to do "s = splhigh(); splx(safepri);
167 * splx(s);" to give interrupts a chance, but there is
168 * no way to give interrupts a chance now.
170 if (lock != NULL && priority & PDROP)
171 class->lc_unlock(lock);
174 catch = priority & PCATCH;
175 pri = priority & PRIMASK;
178 * If we are already on a sleep queue, then remove us from that
179 * sleep queue first. We have to do this to handle recursive
182 if (TD_ON_SLEEPQ(td))
183 sleepq_remove(td, td->td_wchan);
185 if (ident == &pause_wchan)
186 flags = SLEEPQ_PAUSE;
188 flags = SLEEPQ_SLEEP;
190 flags |= SLEEPQ_INTERRUPTIBLE;
191 if (priority & PBDRY)
192 flags |= SLEEPQ_STOP_ON_BDRY;
195 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
196 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
198 if (lock == &Giant.lock_object)
199 mtx_assert(&Giant, MA_OWNED);
201 if (lock != NULL && lock != &Giant.lock_object &&
202 !(class->lc_flags & LC_SLEEPABLE)) {
203 WITNESS_SAVE(lock, lock_witness);
204 lock_state = class->lc_unlock(lock);
206 /* GCC needs to follow the Yellow Brick Road */
210 * We put ourselves on the sleep queue and start our timeout
211 * before calling thread_suspend_check, as we could stop there,
212 * and a wakeup or a SIGCONT (or both) could occur while we were
213 * stopped without resuming us. Thus, we must be ready for sleep
214 * when cursig() is called. If the wakeup happens while we're
215 * stopped, then td will no longer be on a sleep queue upon
216 * return from cursig().
218 sleepq_add(ident, lock, wmesg, flags, 0);
220 sleepq_set_timeout(ident, timo);
221 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
222 sleepq_release(ident);
223 WITNESS_SAVE(lock, lock_witness);
224 lock_state = class->lc_unlock(lock);
228 rval = sleepq_timedwait_sig(ident, pri);
230 rval = sleepq_timedwait(ident, pri);
232 rval = sleepq_wait_sig(ident, pri);
234 sleepq_wait(ident, pri);
238 if (KTRPOINT(td, KTR_CSW))
242 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
243 class->lc_lock(lock, lock_state);
244 WITNESS_RESTORE(lock, lock_witness);
250 msleep_spin(void *ident, struct mtx *mtx, const char *wmesg, int timo)
255 WITNESS_SAVE_DECL(mtx);
259 KASSERT(mtx != NULL, ("sleeping without a mutex"));
260 KASSERT(p != NULL, ("msleep1"));
261 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
265 * During autoconfiguration, just return;
266 * don't run any other threads or panic below,
267 * in case this is the idle thread and already asleep.
268 * XXX: this used to do "s = splhigh(); splx(safepri);
269 * splx(s);" to give interrupts a chance, but there is
270 * no way to give interrupts a chance now.
276 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
277 td->td_tid, p->p_pid, td->td_name, wmesg, ident);
280 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
281 WITNESS_SAVE(&mtx->lock_object, mtx);
282 mtx_unlock_spin(mtx);
285 * We put ourselves on the sleep queue and start our timeout.
287 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
289 sleepq_set_timeout(ident, timo);
292 * Can't call ktrace with any spin locks held so it can lock the
293 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
294 * any spin lock. Thus, we have to drop the sleepq spin lock while
295 * we handle those requests. This is safe since we have placed our
296 * thread on the sleep queue already.
299 if (KTRPOINT(td, KTR_CSW)) {
300 sleepq_release(ident);
306 sleepq_release(ident);
307 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
312 rval = sleepq_timedwait(ident, 0);
314 sleepq_wait(ident, 0);
318 if (KTRPOINT(td, KTR_CSW))
323 WITNESS_RESTORE(&mtx->lock_object, mtx);
328 * pause() is like tsleep() except that the intention is to not be
329 * explicitly woken up by another thread. Instead, the current thread
330 * simply wishes to sleep until the timeout expires. It is
331 * implemented using a dummy wait channel.
334 pause(const char *wmesg, int timo)
337 KASSERT(timo != 0, ("pause: timeout required"));
338 return (tsleep(&pause_wchan, 0, wmesg, timo));
342 * Make all threads sleeping on the specified identifier runnable.
350 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
351 sleepq_release(ident);
352 if (wakeup_swapper) {
353 KASSERT(ident != &proc0,
354 ("wakeup and wakeup_swapper and proc0"));
360 * Make a thread sleeping on the specified identifier runnable.
361 * May wake more than one thread if a target thread is currently
365 wakeup_one(void *ident)
370 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
371 sleepq_release(ident);
379 thread_unlock(curthread);
382 panic("%s: did not reenter debugger", __func__);
386 * The machine independent parts of context switching.
389 mi_switch(int flags, struct thread *newtd)
391 uint64_t runtime, new_switchtime;
395 td = curthread; /* XXX */
396 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
397 p = td->td_proc; /* XXX */
398 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
400 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
401 mtx_assert(&Giant, MA_NOTOWNED);
403 KASSERT(td->td_critnest == 1 || panicstr,
404 ("mi_switch: switch in a critical section"));
405 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
406 ("mi_switch: switch must be voluntary or involuntary"));
407 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
410 * Don't perform context switches from the debugger.
414 if (flags & SW_VOL) {
415 td->td_ru.ru_nvcsw++;
416 td->td_swvoltick = ticks;
418 td->td_ru.ru_nivcsw++;
420 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
423 * Compute the amount of time during which the current
424 * thread was running, and add that to its total so far.
426 new_switchtime = cpu_ticks();
427 runtime = new_switchtime - PCPU_GET(switchtime);
428 td->td_runtime += runtime;
429 td->td_incruntime += runtime;
430 PCPU_SET(switchtime, new_switchtime);
431 td->td_generation++; /* bump preempt-detect counter */
432 PCPU_INC(cnt.v_swtch);
433 PCPU_SET(switchticks, ticks);
434 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
435 td->td_tid, td->td_sched, p->p_pid, td->td_name);
436 #if (KTR_COMPILE & KTR_SCHED) != 0
437 if (TD_IS_IDLETHREAD(td))
438 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "idle",
439 "prio:%d", td->td_priority);
441 KTR_STATE3(KTR_SCHED, "thread", sched_tdname(td), KTDSTATE(td),
442 "prio:%d", td->td_priority, "wmesg:\"%s\"", td->td_wmesg,
443 "lockname:\"%s\"", td->td_lockname);
448 sched_switch(td, newtd, flags);
449 KTR_STATE1(KTR_SCHED, "thread", sched_tdname(td), "running",
450 "prio:%d", td->td_priority);
452 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
453 td->td_tid, td->td_sched, p->p_pid, td->td_name);
456 * If the last thread was exiting, finish cleaning it up.
458 if ((td = PCPU_GET(deadthread))) {
459 PCPU_SET(deadthread, NULL);
465 * Change thread state to be runnable, placing it on the run queue if
466 * it is in memory. If it is swapped out, return true so our caller
467 * will know to awaken the swapper.
470 setrunnable(struct thread *td)
473 THREAD_LOCK_ASSERT(td, MA_OWNED);
474 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
475 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
476 switch (td->td_state) {
482 * If we are only inhibited because we are swapped out
483 * then arange to swap in this process. Otherwise just return.
485 if (td->td_inhibitors != TDI_SWAPPED)
491 printf("state is 0x%x", td->td_state);
492 panic("setrunnable(2)");
494 if ((td->td_flags & TDF_INMEM) == 0) {
495 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
496 td->td_flags |= TDF_SWAPINREQ;
505 * Compute a tenex style load average of a quantity on
506 * 1, 5 and 15 minute intervals.
517 for (i = 0; i < 3; i++)
518 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
519 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
522 * Schedule the next update to occur after 5 seconds, but add a
523 * random variation to avoid synchronisation with processes that
524 * run at regular intervals.
526 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
532 synch_setup(void *dummy)
534 callout_init(&loadav_callout, CALLOUT_MPSAFE);
536 /* Kick off timeout driven events by calling first time. */
544 return (ticks - curthread->td_swvoltick >= hogticks);
552 kern_yield(PRI_USER);
563 if (prio == PRI_USER)
564 prio = td->td_user_pri;
566 sched_prio(td, prio);
567 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
573 * General purpose yield system call.
576 sys_yield(struct thread *td, struct yield_args *uap)
580 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
581 sched_prio(td, PRI_MAX_TIMESHARE);
582 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
584 td->td_retval[0] = 0;