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36 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
39 #include <sys/cdefs.h>
40 __FBSDID("$FreeBSD$");
42 #include "opt_ktrace.h"
43 #include "opt_sched.h"
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/condvar.h>
49 #include <sys/kernel.h>
52 #include <sys/mutex.h>
54 #include <sys/resourcevar.h>
55 #include <sys/sched.h>
57 #include <sys/signalvar.h>
58 #include <sys/sleepqueue.h>
61 #include <sys/sysctl.h>
62 #include <sys/sysproto.h>
63 #include <sys/vmmeter.h>
66 #include <sys/ktrace.h>
69 #include <machine/cpu.h>
71 static void synch_setup(void *dummy);
72 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
76 static uint8_t pause_wchan[MAXCPU];
78 static struct callout loadav_callout;
80 struct loadavg averunnable =
81 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
83 * Constants for averages over 1, 5, and 15 minutes
84 * when sampling at 5 second intervals.
86 static fixpt_t cexp[3] = {
87 0.9200444146293232 * FSCALE, /* exp(-1/12) */
88 0.9834714538216174 * FSCALE, /* exp(-1/60) */
89 0.9944598480048967 * FSCALE, /* exp(-1/180) */
92 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
93 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE, "");
95 static void loadav(void *arg);
97 SDT_PROVIDER_DECLARE(sched);
98 SDT_PROBE_DEFINE(sched, , , preempt);
101 sleepinit(void *unused)
104 hogticks = (hz / 10) * 2; /* Default only. */
109 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
112 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, 0);
115 * General sleep call. Suspends the current thread until a wakeup is
116 * performed on the specified identifier. The thread will then be made
117 * runnable with the specified priority. Sleeps at most sbt units of time
118 * (0 means no timeout). If pri includes the PCATCH flag, let signals
119 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if
120 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
121 * signal becomes pending, ERESTART is returned if the current system
122 * call should be restarted if possible, and EINTR is returned if the system
123 * call should be interrupted by the signal (return EINTR).
125 * The lock argument is unlocked before the caller is suspended, and
126 * re-locked before _sleep() returns. If priority includes the PDROP
127 * flag the lock is not re-locked before returning.
130 _sleep(void *ident, struct lock_object *lock, int priority,
131 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
134 struct lock_class *class;
135 uintptr_t lock_state;
136 int catch, pri, rval, sleepq_flags;
137 WITNESS_SAVE_DECL(lock_witness);
141 if (KTRPOINT(td, KTR_CSW))
144 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
145 "Sleeping on \"%s\"", wmesg);
146 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL,
147 ("sleeping without a lock"));
148 KASSERT(ident != NULL, ("_sleep: NULL ident"));
149 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
150 if (priority & PDROP)
151 KASSERT(lock != NULL && lock != &Giant.lock_object,
152 ("PDROP requires a non-Giant lock"));
154 class = LOCK_CLASS(lock);
158 if (SCHEDULER_STOPPED_TD(td)) {
159 if (lock != NULL && priority & PDROP)
160 class->lc_unlock(lock);
163 catch = priority & PCATCH;
164 pri = priority & PRIMASK;
166 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));
168 if ((uint8_t *)ident >= &pause_wchan[0] &&
169 (uint8_t *)ident <= &pause_wchan[MAXCPU - 1])
170 sleepq_flags = SLEEPQ_PAUSE;
172 sleepq_flags = SLEEPQ_SLEEP;
174 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
177 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
178 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
180 if (lock == &Giant.lock_object)
181 mtx_assert(&Giant, MA_OWNED);
183 if (lock != NULL && lock != &Giant.lock_object &&
184 !(class->lc_flags & LC_SLEEPABLE)) {
185 WITNESS_SAVE(lock, lock_witness);
186 lock_state = class->lc_unlock(lock);
188 /* GCC needs to follow the Yellow Brick Road */
192 * We put ourselves on the sleep queue and start our timeout
193 * before calling thread_suspend_check, as we could stop there,
194 * and a wakeup or a SIGCONT (or both) could occur while we were
195 * stopped without resuming us. Thus, we must be ready for sleep
196 * when cursig() is called. If the wakeup happens while we're
197 * stopped, then td will no longer be on a sleep queue upon
198 * return from cursig().
200 sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
202 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
203 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
204 sleepq_release(ident);
205 WITNESS_SAVE(lock, lock_witness);
206 lock_state = class->lc_unlock(lock);
209 if (sbt != 0 && catch)
210 rval = sleepq_timedwait_sig(ident, pri);
212 rval = sleepq_timedwait(ident, pri);
214 rval = sleepq_wait_sig(ident, pri);
216 sleepq_wait(ident, pri);
220 if (KTRPOINT(td, KTR_CSW))
224 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
225 class->lc_lock(lock, lock_state);
226 WITNESS_RESTORE(lock, lock_witness);
232 msleep_spin_sbt(void *ident, struct mtx *mtx, const char *wmesg,
233 sbintime_t sbt, sbintime_t pr, int flags)
237 WITNESS_SAVE_DECL(mtx);
240 KASSERT(mtx != NULL, ("sleeping without a mutex"));
241 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
242 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));
244 if (SCHEDULER_STOPPED_TD(td))
248 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
249 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
252 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
253 WITNESS_SAVE(&mtx->lock_object, mtx);
254 mtx_unlock_spin(mtx);
257 * We put ourselves on the sleep queue and start our timeout.
259 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
261 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
264 * Can't call ktrace with any spin locks held so it can lock the
265 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
266 * any spin lock. Thus, we have to drop the sleepq spin lock while
267 * we handle those requests. This is safe since we have placed our
268 * thread on the sleep queue already.
271 if (KTRPOINT(td, KTR_CSW)) {
272 sleepq_release(ident);
278 sleepq_release(ident);
279 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
284 rval = sleepq_timedwait(ident, 0);
286 sleepq_wait(ident, 0);
290 if (KTRPOINT(td, KTR_CSW))
295 WITNESS_RESTORE(&mtx->lock_object, mtx);
300 * pause() delays the calling thread by the given number of system ticks.
301 * During cold bootup, pause() uses the DELAY() function instead of
302 * the tsleep() function to do the waiting. The "timo" argument must be
303 * greater than or equal to zero. A "timo" value of zero is equivalent
304 * to a "timo" value of one.
307 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
309 KASSERT(sbt >= 0, ("pause: timeout must be >= 0"));
311 /* silently convert invalid timeouts */
315 if ((cold && curthread == &thread0) || kdb_active ||
316 SCHEDULER_STOPPED()) {
318 * We delay one second at a time to avoid overflowing the
319 * system specific DELAY() function(s):
321 while (sbt >= SBT_1S) {
325 /* Do the delay remainder, if any */
326 sbt = howmany(sbt, SBT_1US);
331 return (_sleep(&pause_wchan[curcpu], NULL, 0, wmesg, sbt, pr, flags));
335 * Make all threads sleeping on the specified identifier runnable.
343 wakeup_swapper = sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
344 sleepq_release(ident);
345 if (wakeup_swapper) {
346 KASSERT(ident != &proc0,
347 ("wakeup and wakeup_swapper and proc0"));
353 * Make a thread sleeping on the specified identifier runnable.
354 * May wake more than one thread if a target thread is currently
358 wakeup_one(void *ident)
363 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP, 0, 0);
364 sleepq_release(ident);
372 thread_unlock(curthread);
375 panic("%s: did not reenter debugger", __func__);
379 * The machine independent parts of context switching.
382 mi_switch(int flags, struct thread *newtd)
384 uint64_t runtime, new_switchtime;
387 td = curthread; /* XXX */
388 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
389 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
391 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
392 mtx_assert(&Giant, MA_NOTOWNED);
394 KASSERT(td->td_critnest == 1 || 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.
405 if (SCHEDULER_STOPPED_TD(td))
407 if (flags & SW_VOL) {
408 td->td_ru.ru_nvcsw++;
409 td->td_swvoltick = ticks;
411 td->td_ru.ru_nivcsw++;
412 td->td_swinvoltick = ticks;
415 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
418 * Compute the amount of time during which the current
419 * thread was running, and add that to its total so far.
421 new_switchtime = cpu_ticks();
422 runtime = new_switchtime - PCPU_GET(switchtime);
423 td->td_runtime += runtime;
424 td->td_incruntime += runtime;
425 PCPU_SET(switchtime, new_switchtime);
426 td->td_generation++; /* bump preempt-detect counter */
428 PCPU_SET(switchticks, ticks);
429 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
430 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
432 if ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
433 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED))
434 SDT_PROBE0(sched, , , preempt);
436 sched_switch(td, newtd, flags);
437 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
438 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
441 * If the last thread was exiting, finish cleaning it up.
443 if ((td = PCPU_GET(deadthread))) {
444 PCPU_SET(deadthread, NULL);
450 * Change thread state to be runnable, placing it on the run queue if
451 * it is in memory. If it is swapped out, return true so our caller
452 * will know to awaken the swapper.
455 setrunnable(struct thread *td)
458 THREAD_LOCK_ASSERT(td, MA_OWNED);
459 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
460 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
461 switch (td->td_state) {
467 * If we are only inhibited because we are swapped out
468 * then arange to swap in this process. Otherwise just return.
470 if (td->td_inhibitors != TDI_SWAPPED)
476 printf("state is 0x%x", td->td_state);
477 panic("setrunnable(2)");
479 if ((td->td_flags & TDF_INMEM) == 0) {
480 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
481 td->td_flags |= TDF_SWAPINREQ;
490 * Compute a tenex style load average of a quantity on
491 * 1, 5 and 15 minute intervals.
502 for (i = 0; i < 3; i++)
503 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
504 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
507 * Schedule the next update to occur after 5 seconds, but add a
508 * random variation to avoid synchronisation with processes that
509 * run at regular intervals.
511 callout_reset_sbt(&loadav_callout,
512 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
513 loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
518 synch_setup(void *dummy)
520 callout_init(&loadav_callout, 1);
522 /* Kick off timeout driven events by calling first time. */
530 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
538 kern_yield(PRI_USER);
549 if (prio == PRI_USER)
550 prio = td->td_user_pri;
552 sched_prio(td, prio);
553 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
559 * General purpose yield system call.
562 sys_yield(struct thread *td, struct yield_args *uap)
566 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
567 sched_prio(td, PRI_MAX_TIMESHARE);
568 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
570 td->td_retval[0] = 0;