1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1990, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37 #include <sys/cdefs.h>
38 #include "opt_ktrace.h"
39 #include "opt_sched.h"
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/blockcount.h>
44 #include <sys/condvar.h>
45 #include <sys/kdb.h>
46 #include <sys/kernel.h>
47 #include <sys/ktr.h>
48 #include <sys/ktrace.h>
49 #include <sys/lock.h>
50 #include <sys/mutex.h>
51 #include <sys/proc.h>
52 #include <sys/resourcevar.h>
53 #include <sys/sched.h>
54 #include <sys/sdt.h>
55 #include <sys/signalvar.h>
56 #include <sys/sleepqueue.h>
57 #include <sys/smp.h>
58 #include <sys/sx.h>
59 #include <sys/sysctl.h>
60 #include <sys/sysproto.h>
61 #include <sys/vmmeter.h>
62 #ifdef KTRACE
63 #include <sys/uio.h>
64 #endif
65 #ifdef EPOCH_TRACE
66 #include <sys/epoch.h>
67 #endif
68
69 #include <machine/cpu.h>
70
71 static void synch_setup(void *dummy);
72 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup,
73 NULL);
74
75 int hogticks;
76 static const char pause_wchan[MAXCPU];
77
78 static struct callout loadav_callout;
79
80 struct loadavg averunnable =
81 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
82 /*
83 * Constants for averages over 1, 5, and 15 minutes
84 * when sampling at 5 second intervals.
85 */
86 static uint64_t cexp[3] = {
87 0.9200444146293232 * FSCALE, /* exp(-1/12) */
88 0.9834714538216174 * FSCALE, /* exp(-1/60) */
89 0.9944598480048967 * FSCALE, /* exp(-1/180) */
90 };
91
92 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
93 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, SYSCTL_NULL_INT_PTR, FSCALE,
94 "Fixed-point scale factor used for calculating load average values");
95
96 static void loadav(void *arg);
97
98 SDT_PROVIDER_DECLARE(sched);
99 SDT_PROBE_DEFINE(sched, , , preempt);
100
101 static void
sleepinit(void * unused)102 sleepinit(void *unused)
103 {
104
105 hogticks = (hz / 10) * 2; /* Default only. */
106 init_sleepqueues();
107 }
108
109 /*
110 * vmem tries to lock the sleepq mutexes when free'ing kva, so make sure
111 * it is available.
112 */
113 SYSINIT(sleepinit, SI_SUB_KMEM, SI_ORDER_ANY, sleepinit, NULL);
114
115 /*
116 * General sleep call. Suspends the current thread until a wakeup is
117 * performed on the specified identifier. The thread will then be made
118 * runnable with the specified priority. Sleeps at most sbt units of time
119 * (0 means no timeout). If pri includes the PCATCH flag, let signals
120 * interrupt the sleep, otherwise ignore them while sleeping. Returns 0 if
121 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
122 * signal becomes pending, ERESTART is returned if the current system
123 * call should be restarted if possible, and EINTR is returned if the system
124 * call should be interrupted by the signal (return EINTR).
125 *
126 * The lock argument is unlocked before the caller is suspended, and
127 * re-locked before _sleep() returns. If priority includes the PDROP
128 * flag the lock is not re-locked before returning.
129 */
130 int
_sleep(const void * ident,struct lock_object * lock,int priority,const char * wmesg,sbintime_t sbt,sbintime_t pr,int flags)131 _sleep(const void *ident, struct lock_object *lock, int priority,
132 const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
133 {
134 struct thread *td __ktrace_used;
135 struct lock_class *class;
136 uintptr_t lock_state;
137 int catch, pri, rval, sleepq_flags;
138 WITNESS_SAVE_DECL(lock_witness);
139
140 TSENTER();
141 td = curthread;
142 #ifdef KTRACE
143 if (KTRPOINT(td, KTR_CSW))
144 ktrcsw(1, 0, wmesg);
145 #endif
146 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
147 "Sleeping on \"%s\"", wmesg);
148 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL ||
149 (priority & PNOLOCK) != 0,
150 ("sleeping without a lock"));
151 KASSERT(ident != NULL, ("_sleep: NULL ident"));
152 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
153 if (priority & PDROP)
154 KASSERT(lock != NULL && lock != &Giant.lock_object,
155 ("PDROP requires a non-Giant lock"));
156 if (lock != NULL)
157 class = LOCK_CLASS(lock);
158 else
159 class = NULL;
160
161 if (SCHEDULER_STOPPED()) {
162 if (lock != NULL && priority & PDROP)
163 class->lc_unlock(lock);
164 return (0);
165 }
166 catch = priority & PCATCH;
167 pri = priority & PRIMASK;
168
169 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));
170
171 if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] &&
172 (uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1])
173 sleepq_flags = SLEEPQ_PAUSE;
174 else
175 sleepq_flags = SLEEPQ_SLEEP;
176 if (catch)
177 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
178
179 sleepq_lock(ident);
180 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
181 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
182
183 if (lock == &Giant.lock_object)
184 mtx_assert(&Giant, MA_OWNED);
185 DROP_GIANT();
186 if (lock != NULL && lock != &Giant.lock_object &&
187 !(class->lc_flags & LC_SLEEPABLE)) {
188 KASSERT(!(class->lc_flags & LC_SPINLOCK),
189 ("spin locks can only use msleep_spin"));
190 WITNESS_SAVE(lock, lock_witness);
191 lock_state = class->lc_unlock(lock);
192 } else
193 /* GCC needs to follow the Yellow Brick Road */
194 lock_state = -1;
195
196 /*
197 * We put ourselves on the sleep queue and start our timeout
198 * before calling thread_suspend_check, as we could stop there,
199 * and a wakeup or a SIGCONT (or both) could occur while we were
200 * stopped without resuming us. Thus, we must be ready for sleep
201 * when cursig() is called. If the wakeup happens while we're
202 * stopped, then td will no longer be on a sleep queue upon
203 * return from cursig().
204 */
205 sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
206 if (sbt != 0)
207 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
208 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
209 sleepq_release(ident);
210 WITNESS_SAVE(lock, lock_witness);
211 lock_state = class->lc_unlock(lock);
212 sleepq_lock(ident);
213 }
214 if (sbt != 0 && catch)
215 rval = sleepq_timedwait_sig(ident, pri);
216 else if (sbt != 0)
217 rval = sleepq_timedwait(ident, pri);
218 else if (catch)
219 rval = sleepq_wait_sig(ident, pri);
220 else {
221 sleepq_wait(ident, pri);
222 rval = 0;
223 }
224 #ifdef KTRACE
225 if (KTRPOINT(td, KTR_CSW))
226 ktrcsw(0, 0, wmesg);
227 #endif
228 PICKUP_GIANT();
229 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
230 class->lc_lock(lock, lock_state);
231 WITNESS_RESTORE(lock, lock_witness);
232 }
233 TSEXIT();
234 return (rval);
235 }
236
237 int
msleep_spin_sbt(const void * ident,struct mtx * mtx,const char * wmesg,sbintime_t sbt,sbintime_t pr,int flags)238 msleep_spin_sbt(const void *ident, struct mtx *mtx, const char *wmesg,
239 sbintime_t sbt, sbintime_t pr, int flags)
240 {
241 struct thread *td __ktrace_used;
242 int rval;
243 WITNESS_SAVE_DECL(mtx);
244
245 td = curthread;
246 KASSERT(mtx != NULL, ("sleeping without a mutex"));
247 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
248 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));
249
250 if (SCHEDULER_STOPPED())
251 return (0);
252
253 sleepq_lock(ident);
254 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
255 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
256
257 DROP_GIANT();
258 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
259 WITNESS_SAVE(&mtx->lock_object, mtx);
260 mtx_unlock_spin(mtx);
261
262 /*
263 * We put ourselves on the sleep queue and start our timeout.
264 */
265 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
266 if (sbt != 0)
267 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
268
269 /*
270 * Can't call ktrace with any spin locks held so it can lock the
271 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
272 * any spin lock. Thus, we have to drop the sleepq spin lock while
273 * we handle those requests. This is safe since we have placed our
274 * thread on the sleep queue already.
275 */
276 #ifdef KTRACE
277 if (KTRPOINT(td, KTR_CSW)) {
278 sleepq_release(ident);
279 ktrcsw(1, 0, wmesg);
280 sleepq_lock(ident);
281 }
282 #endif
283 #ifdef WITNESS
284 sleepq_release(ident);
285 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
286 wmesg);
287 sleepq_lock(ident);
288 #endif
289 if (sbt != 0)
290 rval = sleepq_timedwait(ident, 0);
291 else {
292 sleepq_wait(ident, 0);
293 rval = 0;
294 }
295 #ifdef KTRACE
296 if (KTRPOINT(td, KTR_CSW))
297 ktrcsw(0, 0, wmesg);
298 #endif
299 PICKUP_GIANT();
300 mtx_lock_spin(mtx);
301 WITNESS_RESTORE(&mtx->lock_object, mtx);
302 return (rval);
303 }
304
305 /*
306 * pause_sbt() delays the calling thread by the given signed binary
307 * time. During cold bootup, pause_sbt() uses the DELAY() function
308 * instead of the _sleep() function to do the waiting. The "sbt"
309 * argument must be greater than or equal to zero. A "sbt" value of
310 * zero is equivalent to a "sbt" value of one tick.
311 */
312 int
pause_sbt(const char * wmesg,sbintime_t sbt,sbintime_t pr,int flags)313 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
314 {
315 KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0"));
316
317 /* silently convert invalid timeouts */
318 if (sbt == 0)
319 sbt = tick_sbt;
320
321 if ((cold && curthread == &thread0) || kdb_active ||
322 SCHEDULER_STOPPED()) {
323 /*
324 * We delay one second at a time to avoid overflowing the
325 * system specific DELAY() function(s):
326 */
327 while (sbt >= SBT_1S) {
328 DELAY(1000000);
329 sbt -= SBT_1S;
330 }
331 /* Do the delay remainder, if any */
332 sbt = howmany(sbt, SBT_1US);
333 if (sbt > 0)
334 DELAY(sbt);
335 return (EWOULDBLOCK);
336 }
337 return (_sleep(&pause_wchan[curcpu], NULL,
338 (flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags));
339 }
340
341 /*
342 * Make all threads sleeping on the specified identifier runnable.
343 */
344 void
wakeup(const void * ident)345 wakeup(const void *ident)
346 {
347 int wakeup_swapper;
348
349 sleepq_lock(ident);
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"));
355 kick_proc0();
356 }
357 }
358
359 /*
360 * Make a thread sleeping on the specified identifier runnable.
361 * May wake more than one thread if a target thread is currently
362 * swapped out.
363 */
364 void
wakeup_one(const void * ident)365 wakeup_one(const void *ident)
366 {
367 int wakeup_swapper;
368
369 sleepq_lock(ident);
370 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0);
371 if (wakeup_swapper)
372 kick_proc0();
373 }
374
375 void
wakeup_any(const void * ident)376 wakeup_any(const void *ident)
377 {
378 int wakeup_swapper;
379
380 sleepq_lock(ident);
381 wakeup_swapper = sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR |
382 SLEEPQ_DROP, 0, 0);
383 if (wakeup_swapper)
384 kick_proc0();
385 }
386
387 /*
388 * Signal sleeping waiters after the counter has reached zero.
389 */
390 void
_blockcount_wakeup(blockcount_t * bc,u_int old)391 _blockcount_wakeup(blockcount_t *bc, u_int old)
392 {
393
394 KASSERT(_BLOCKCOUNT_WAITERS(old),
395 ("%s: no waiters on %p", __func__, bc));
396
397 if (atomic_cmpset_int(&bc->__count, _BLOCKCOUNT_WAITERS_FLAG, 0))
398 wakeup(bc);
399 }
400
401 /*
402 * Wait for a wakeup or a signal. This does not guarantee that the count is
403 * still zero on return. Callers wanting a precise answer should use
404 * blockcount_wait() with an interlock.
405 *
406 * If there is no work to wait for, return 0. If the sleep was interrupted by a
407 * signal, return EINTR or ERESTART, and return EAGAIN otherwise.
408 */
409 int
_blockcount_sleep(blockcount_t * bc,struct lock_object * lock,const char * wmesg,int prio)410 _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
411 int prio)
412 {
413 void *wchan;
414 uintptr_t lock_state;
415 u_int old;
416 int ret;
417 bool catch, drop;
418
419 KASSERT(lock != &Giant.lock_object,
420 ("%s: cannot use Giant as the interlock", __func__));
421
422 catch = (prio & PCATCH) != 0;
423 drop = (prio & PDROP) != 0;
424 prio &= PRIMASK;
425
426 /*
427 * Synchronize with the fence in blockcount_release(). If we end up
428 * waiting, the sleepqueue lock acquisition will provide the required
429 * side effects.
430 *
431 * If there is no work to wait for, but waiters are present, try to put
432 * ourselves to sleep to avoid jumping ahead.
433 */
434 if (atomic_load_acq_int(&bc->__count) == 0) {
435 if (lock != NULL && drop)
436 LOCK_CLASS(lock)->lc_unlock(lock);
437 return (0);
438 }
439 lock_state = 0;
440 wchan = bc;
441 sleepq_lock(wchan);
442 DROP_GIANT();
443 if (lock != NULL)
444 lock_state = LOCK_CLASS(lock)->lc_unlock(lock);
445 old = blockcount_read(bc);
446 ret = 0;
447 do {
448 if (_BLOCKCOUNT_COUNT(old) == 0) {
449 sleepq_release(wchan);
450 goto out;
451 }
452 if (_BLOCKCOUNT_WAITERS(old))
453 break;
454 } while (!atomic_fcmpset_int(&bc->__count, &old,
455 old | _BLOCKCOUNT_WAITERS_FLAG));
456 sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0);
457 if (catch)
458 ret = sleepq_wait_sig(wchan, prio);
459 else
460 sleepq_wait(wchan, prio);
461 if (ret == 0)
462 ret = EAGAIN;
463
464 out:
465 PICKUP_GIANT();
466 if (lock != NULL && !drop)
467 LOCK_CLASS(lock)->lc_lock(lock, lock_state);
468
469 return (ret);
470 }
471
472 static void
kdb_switch(void)473 kdb_switch(void)
474 {
475 thread_unlock(curthread);
476 kdb_backtrace();
477 kdb_reenter();
478 panic("%s: did not reenter debugger", __func__);
479 }
480
481 /*
482 * mi_switch(9): The machine-independent parts of context switching.
483 *
484 * The thread lock is required on entry and is no longer held on return.
485 */
486 void
mi_switch(int flags)487 mi_switch(int flags)
488 {
489 uint64_t runtime, new_switchtime;
490 struct thread *td;
491
492 td = curthread; /* XXX */
493 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
494 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
495 #ifdef INVARIANTS
496 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
497 mtx_assert(&Giant, MA_NOTOWNED);
498 #endif
499 /* thread_lock() performs spinlock_enter(). */
500 KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(),
501 ("mi_switch: switch in a critical section"));
502 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
503 ("mi_switch: switch must be voluntary or involuntary"));
504 KASSERT((flags & SW_TYPE_MASK) != 0,
505 ("mi_switch: a switch reason (type) must be specified"));
506 KASSERT((flags & SW_TYPE_MASK) < SWT_COUNT,
507 ("mi_switch: invalid switch reason %d", (flags & SW_TYPE_MASK)));
508
509 /*
510 * Don't perform context switches from the debugger.
511 */
512 if (kdb_active)
513 kdb_switch();
514 if (SCHEDULER_STOPPED())
515 return;
516 if (flags & SW_VOL) {
517 td->td_ru.ru_nvcsw++;
518 td->td_swvoltick = ticks;
519 } else {
520 td->td_ru.ru_nivcsw++;
521 td->td_swinvoltick = ticks;
522 }
523 #ifdef SCHED_STATS
524 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
525 #endif
526 /*
527 * Compute the amount of time during which the current
528 * thread was running, and add that to its total so far.
529 */
530 new_switchtime = cpu_ticks();
531 runtime = new_switchtime - PCPU_GET(switchtime);
532 td->td_runtime += runtime;
533 td->td_incruntime += runtime;
534 PCPU_SET(switchtime, new_switchtime);
535 td->td_generation++; /* bump preempt-detect counter */
536 VM_CNT_INC(v_swtch);
537 PCPU_SET(switchticks, ticks);
538 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
539 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
540 #ifdef KDTRACE_HOOKS
541 if (SDT_PROBES_ENABLED() &&
542 ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
543 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED)))
544 SDT_PROBE0(sched, , , preempt);
545 #endif
546 sched_switch(td, flags);
547 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
548 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
549
550 /*
551 * If the last thread was exiting, finish cleaning it up.
552 */
553 if ((td = PCPU_GET(deadthread))) {
554 PCPU_SET(deadthread, NULL);
555 thread_stash(td);
556 }
557 spinlock_exit();
558 }
559
560 /*
561 * Change thread state to be runnable, placing it on the run queue if
562 * it is in memory. If it is swapped out, return true so our caller
563 * will know to awaken the swapper.
564 *
565 * Requires the thread lock on entry, drops on exit.
566 */
567 int
setrunnable(struct thread * td,int srqflags)568 setrunnable(struct thread *td, int srqflags)
569 {
570 int swapin;
571
572 THREAD_LOCK_ASSERT(td, MA_OWNED);
573 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
574 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
575
576 swapin = 0;
577 switch (TD_GET_STATE(td)) {
578 case TDS_RUNNING:
579 case TDS_RUNQ:
580 break;
581 case TDS_CAN_RUN:
582 KASSERT((td->td_flags & TDF_INMEM) != 0,
583 ("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X",
584 td, td->td_flags, td->td_inhibitors));
585 /* unlocks thread lock according to flags */
586 sched_wakeup(td, srqflags);
587 return (0);
588 case TDS_INHIBITED:
589 /*
590 * If we are only inhibited because we are swapped out
591 * arrange to swap in this process.
592 */
593 if (td->td_inhibitors == TDI_SWAPPED &&
594 (td->td_flags & TDF_SWAPINREQ) == 0) {
595 td->td_flags |= TDF_SWAPINREQ;
596 swapin = 1;
597 }
598 break;
599 default:
600 panic("setrunnable: state 0x%x", TD_GET_STATE(td));
601 }
602 if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0)
603 thread_unlock(td);
604
605 return (swapin);
606 }
607
608 /*
609 * Compute a tenex style load average of a quantity on
610 * 1, 5 and 15 minute intervals.
611 */
612 static void
loadav(void * arg)613 loadav(void *arg)
614 {
615 int i;
616 uint64_t nrun;
617 struct loadavg *avg;
618
619 nrun = (uint64_t)sched_load();
620 avg = &averunnable;
621
622 for (i = 0; i < 3; i++)
623 avg->ldavg[i] = (cexp[i] * (uint64_t)avg->ldavg[i] +
624 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
625
626 /*
627 * Schedule the next update to occur after 5 seconds, but add a
628 * random variation to avoid synchronisation with processes that
629 * run at regular intervals.
630 */
631 callout_reset_sbt(&loadav_callout,
632 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
633 loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
634 }
635
636 static void
ast_scheduler(struct thread * td,int tda __unused)637 ast_scheduler(struct thread *td, int tda __unused)
638 {
639 #ifdef KTRACE
640 if (KTRPOINT(td, KTR_CSW))
641 ktrcsw(1, 1, __func__);
642 #endif
643 thread_lock(td);
644 sched_prio(td, td->td_user_pri);
645 mi_switch(SW_INVOL | SWT_NEEDRESCHED);
646 #ifdef KTRACE
647 if (KTRPOINT(td, KTR_CSW))
648 ktrcsw(0, 1, __func__);
649 #endif
650 }
651
652 static void
synch_setup(void * dummy __unused)653 synch_setup(void *dummy __unused)
654 {
655 callout_init(&loadav_callout, 1);
656 ast_register(TDA_SCHED, ASTR_ASTF_REQUIRED, 0, ast_scheduler);
657
658 /* Kick off timeout driven events by calling first time. */
659 loadav(NULL);
660 }
661
662 bool
should_yield(void)663 should_yield(void)
664 {
665
666 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
667 }
668
669 void
maybe_yield(void)670 maybe_yield(void)
671 {
672
673 if (should_yield())
674 kern_yield(PRI_USER);
675 }
676
677 void
kern_yield(int prio)678 kern_yield(int prio)
679 {
680 struct thread *td;
681
682 td = curthread;
683 DROP_GIANT();
684 thread_lock(td);
685 if (prio == PRI_USER)
686 prio = td->td_user_pri;
687 if (prio >= 0)
688 sched_prio(td, prio);
689 mi_switch(SW_VOL | SWT_RELINQUISH);
690 PICKUP_GIANT();
691 }
692
693 /*
694 * General purpose yield system call.
695 */
696 int
sys_yield(struct thread * td,struct yield_args * uap)697 sys_yield(struct thread *td, struct yield_args *uap)
698 {
699
700 thread_lock(td);
701 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
702 sched_prio(td, PRI_MAX_TIMESHARE);
703 mi_switch(SW_VOL | SWT_RELINQUISH);
704 td->td_retval[0] = 0;
705 return (0);
706 }
707
708 int
sys_sched_getcpu(struct thread * td,struct sched_getcpu_args * uap)709 sys_sched_getcpu(struct thread *td, struct sched_getcpu_args *uap)
710 {
711 td->td_retval[0] = td->td_oncpu;
712 return (0);
713 }
714