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 struct timespec sw_out_tv __ktrace_used;
137 uintptr_t lock_state;
138 int catch, pri, rval, sleepq_flags;
139 WITNESS_SAVE_DECL(lock_witness);
140
141 TSENTER();
142 td = curthread;
143 #ifdef KTRACE
144 if (KTRPOINT(td, KTR_CSW))
145 nanotime(&sw_out_tv);
146 #endif
147 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
148 "Sleeping on \"%s\"", wmesg);
149 KASSERT(sbt != 0 || mtx_owned(&Giant) || lock != NULL ||
150 (priority & PNOLOCK) != 0,
151 ("sleeping without a lock"));
152 KASSERT(ident != NULL, ("_sleep: NULL ident"));
153 KASSERT(TD_IS_RUNNING(td), ("_sleep: curthread not running"));
154 if (priority & PDROP)
155 KASSERT(lock != NULL && lock != &Giant.lock_object,
156 ("PDROP requires a non-Giant lock"));
157 if (lock != NULL)
158 class = LOCK_CLASS(lock);
159 else
160 class = NULL;
161
162 if (SCHEDULER_STOPPED()) {
163 if (lock != NULL && priority & PDROP)
164 class->lc_unlock(lock);
165 return (0);
166 }
167 catch = priority & PCATCH;
168 pri = priority & PRIMASK;
169
170 KASSERT(!TD_ON_SLEEPQ(td), ("recursive sleep"));
171
172 if ((uintptr_t)ident >= (uintptr_t)&pause_wchan[0] &&
173 (uintptr_t)ident <= (uintptr_t)&pause_wchan[MAXCPU - 1])
174 sleepq_flags = SLEEPQ_PAUSE;
175 else
176 sleepq_flags = SLEEPQ_SLEEP;
177 if (catch)
178 sleepq_flags |= SLEEPQ_INTERRUPTIBLE;
179
180 sleepq_lock(ident);
181 CTR5(KTR_PROC, "sleep: thread %ld (pid %ld, %s) on %s (%p)",
182 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
183
184 if (lock == &Giant.lock_object)
185 mtx_assert(&Giant, MA_OWNED);
186 DROP_GIANT();
187 if (lock != NULL && lock != &Giant.lock_object &&
188 !(class->lc_flags & LC_SLEEPABLE)) {
189 KASSERT(!(class->lc_flags & LC_SPINLOCK),
190 ("spin locks can only use msleep_spin"));
191 WITNESS_SAVE(lock, lock_witness);
192 lock_state = class->lc_unlock(lock);
193 } else
194 /* GCC needs to follow the Yellow Brick Road */
195 lock_state = -1;
196
197 /*
198 * We put ourselves on the sleep queue and start our timeout
199 * before calling thread_suspend_check, as we could stop there,
200 * and a wakeup or a SIGCONT (or both) could occur while we were
201 * stopped without resuming us. Thus, we must be ready for sleep
202 * when cursig() is called. If the wakeup happens while we're
203 * stopped, then td will no longer be on a sleep queue upon
204 * return from cursig().
205 */
206 sleepq_add(ident, lock, wmesg, sleepq_flags, 0);
207 if (sbt != 0)
208 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
209 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
210 sleepq_release(ident);
211 WITNESS_SAVE(lock, lock_witness);
212 lock_state = class->lc_unlock(lock);
213 sleepq_lock(ident);
214 }
215 if (sbt != 0 && catch)
216 rval = sleepq_timedwait_sig(ident, pri);
217 else if (sbt != 0)
218 rval = sleepq_timedwait(ident, pri);
219 else if (catch)
220 rval = sleepq_wait_sig(ident, pri);
221 else {
222 sleepq_wait(ident, pri);
223 rval = 0;
224 }
225 #ifdef KTRACE
226 if (KTRPOINT(td, KTR_CSW)) {
227 ktrcsw_out(&sw_out_tv, wmesg);
228 ktrcsw(0, 0, wmesg);
229 }
230 #endif
231 PICKUP_GIANT();
232 if (lock != NULL && lock != &Giant.lock_object && !(priority & PDROP)) {
233 class->lc_lock(lock, lock_state);
234 WITNESS_RESTORE(lock, lock_witness);
235 }
236 TSEXIT();
237 return (rval);
238 }
239
240 int
msleep_spin_sbt(const void * ident,struct mtx * mtx,const char * wmesg,sbintime_t sbt,sbintime_t pr,int flags)241 msleep_spin_sbt(const void *ident, struct mtx *mtx, const char *wmesg,
242 sbintime_t sbt, sbintime_t pr, int flags)
243 {
244 struct thread *td __ktrace_used;
245 struct timespec sw_out_tv __ktrace_used;
246 int rval;
247 WITNESS_SAVE_DECL(mtx);
248
249 td = curthread;
250 KASSERT(mtx != NULL, ("sleeping without a mutex"));
251 KASSERT(ident != NULL, ("msleep_spin_sbt: NULL ident"));
252 KASSERT(TD_IS_RUNNING(td), ("msleep_spin_sbt: curthread not running"));
253
254 if (SCHEDULER_STOPPED())
255 return (0);
256
257 sleepq_lock(ident);
258 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
259 td->td_tid, td->td_proc->p_pid, td->td_name, wmesg, ident);
260
261 DROP_GIANT();
262 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
263 WITNESS_SAVE(&mtx->lock_object, mtx);
264 mtx_unlock_spin(mtx);
265
266 /*
267 * We put ourselves on the sleep queue and start our timeout.
268 */
269 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
270 if (sbt != 0)
271 sleepq_set_timeout_sbt(ident, sbt, pr, flags);
272
273 #ifdef KTRACE
274 if (KTRPOINT(td, KTR_CSW))
275 nanotime(&sw_out_tv);
276 #endif
277 #ifdef WITNESS
278 sleepq_release(ident);
279 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
280 wmesg);
281 sleepq_lock(ident);
282 #endif
283 if (sbt != 0)
284 rval = sleepq_timedwait(ident, 0);
285 else {
286 sleepq_wait(ident, 0);
287 rval = 0;
288 }
289 #ifdef KTRACE
290 if (KTRPOINT(td, KTR_CSW)) {
291 ktrcsw_out(&sw_out_tv, wmesg);
292 ktrcsw(0, 0, wmesg);
293 }
294 #endif
295 PICKUP_GIANT();
296 mtx_lock_spin(mtx);
297 WITNESS_RESTORE(&mtx->lock_object, mtx);
298 return (rval);
299 }
300
301 /*
302 * pause_sbt() delays the calling thread by the given signed binary
303 * time. During cold bootup, pause_sbt() uses the DELAY() function
304 * instead of the _sleep() function to do the waiting. The "sbt"
305 * argument must be greater than or equal to zero. A "sbt" value of
306 * zero is equivalent to a "sbt" value of one tick.
307 */
308 int
pause_sbt(const char * wmesg,sbintime_t sbt,sbintime_t pr,int flags)309 pause_sbt(const char *wmesg, sbintime_t sbt, sbintime_t pr, int flags)
310 {
311 KASSERT(sbt >= 0, ("pause_sbt: timeout must be >= 0"));
312
313 /* silently convert invalid timeouts */
314 if (sbt == 0)
315 sbt = tick_sbt;
316
317 if ((cold && curthread == &thread0) || kdb_active ||
318 SCHEDULER_STOPPED()) {
319 /*
320 * We delay one second at a time to avoid overflowing the
321 * system specific DELAY() function(s):
322 */
323 while (sbt >= SBT_1S) {
324 DELAY(1000000);
325 sbt -= SBT_1S;
326 }
327 /* Do the delay remainder, if any */
328 sbt = howmany(sbt, SBT_1US);
329 if (sbt > 0)
330 DELAY(sbt);
331 return (EWOULDBLOCK);
332 }
333 return (_sleep(&pause_wchan[curcpu], NULL,
334 (flags & C_CATCH) ? PCATCH : 0, wmesg, sbt, pr, flags));
335 }
336
337 /*
338 * Make all threads sleeping on the specified identifier runnable.
339 */
340 void
wakeup(const void * ident)341 wakeup(const void *ident)
342 {
343 sleepq_lock(ident);
344 sleepq_broadcast(ident, SLEEPQ_SLEEP, 0, 0);
345 sleepq_release(ident);
346 }
347
348 /*
349 * Make a thread sleeping on the specified identifier runnable.
350 * May wake more than one thread if a target thread is currently
351 * swapped out.
352 */
353 void
wakeup_one(const void * ident)354 wakeup_one(const void *ident)
355 {
356 sleepq_lock(ident);
357 sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_DROP, 0, 0);
358 }
359
360 void
wakeup_any(const void * ident)361 wakeup_any(const void *ident)
362 {
363 sleepq_lock(ident);
364 sleepq_signal(ident, SLEEPQ_SLEEP | SLEEPQ_UNFAIR | SLEEPQ_DROP, 0, 0);
365 }
366
367 /*
368 * Signal sleeping waiters after the counter has reached zero.
369 */
370 void
_blockcount_wakeup(blockcount_t * bc,u_int old)371 _blockcount_wakeup(blockcount_t *bc, u_int old)
372 {
373
374 KASSERT(_BLOCKCOUNT_WAITERS(old),
375 ("%s: no waiters on %p", __func__, bc));
376
377 if (atomic_cmpset_int(&bc->__count, _BLOCKCOUNT_WAITERS_FLAG, 0))
378 wakeup(bc);
379 }
380
381 /*
382 * Wait for a wakeup or a signal. This does not guarantee that the count is
383 * still zero on return. Callers wanting a precise answer should use
384 * blockcount_wait() with an interlock.
385 *
386 * If there is no work to wait for, return 0. If the sleep was interrupted by a
387 * signal, return EINTR or ERESTART, and return EAGAIN otherwise.
388 */
389 int
_blockcount_sleep(blockcount_t * bc,struct lock_object * lock,const char * wmesg,int prio)390 _blockcount_sleep(blockcount_t *bc, struct lock_object *lock, const char *wmesg,
391 int prio)
392 {
393 void *wchan;
394 uintptr_t lock_state;
395 u_int old;
396 int ret;
397 bool catch, drop;
398
399 KASSERT(lock != &Giant.lock_object,
400 ("%s: cannot use Giant as the interlock", __func__));
401
402 catch = (prio & PCATCH) != 0;
403 drop = (prio & PDROP) != 0;
404 prio &= PRIMASK;
405
406 /*
407 * Synchronize with the fence in blockcount_release(). If we end up
408 * waiting, the sleepqueue lock acquisition will provide the required
409 * side effects.
410 *
411 * If there is no work to wait for, but waiters are present, try to put
412 * ourselves to sleep to avoid jumping ahead.
413 */
414 if (atomic_load_acq_int(&bc->__count) == 0) {
415 if (lock != NULL && drop)
416 LOCK_CLASS(lock)->lc_unlock(lock);
417 return (0);
418 }
419 lock_state = 0;
420 wchan = bc;
421 sleepq_lock(wchan);
422 DROP_GIANT();
423 if (lock != NULL)
424 lock_state = LOCK_CLASS(lock)->lc_unlock(lock);
425 old = blockcount_read(bc);
426 ret = 0;
427 do {
428 if (_BLOCKCOUNT_COUNT(old) == 0) {
429 sleepq_release(wchan);
430 goto out;
431 }
432 if (_BLOCKCOUNT_WAITERS(old))
433 break;
434 } while (!atomic_fcmpset_int(&bc->__count, &old,
435 old | _BLOCKCOUNT_WAITERS_FLAG));
436 sleepq_add(wchan, NULL, wmesg, catch ? SLEEPQ_INTERRUPTIBLE : 0, 0);
437 if (catch)
438 ret = sleepq_wait_sig(wchan, prio);
439 else
440 sleepq_wait(wchan, prio);
441 if (ret == 0)
442 ret = EAGAIN;
443
444 out:
445 PICKUP_GIANT();
446 if (lock != NULL && !drop)
447 LOCK_CLASS(lock)->lc_lock(lock, lock_state);
448
449 return (ret);
450 }
451
452 static void
kdb_switch(void)453 kdb_switch(void)
454 {
455 thread_unlock(curthread);
456 kdb_backtrace();
457 kdb_reenter();
458 panic("%s: did not reenter debugger", __func__);
459 }
460
461 /*
462 * mi_switch(9): The machine-independent parts of context switching.
463 *
464 * The thread lock is required on entry and is no longer held on return.
465 */
466 void
mi_switch(int flags)467 mi_switch(int flags)
468 {
469 uint64_t runtime, new_switchtime;
470 struct thread *td;
471
472 td = curthread; /* XXX */
473 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
474 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
475 #ifdef INVARIANTS
476 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
477 mtx_assert(&Giant, MA_NOTOWNED);
478 #endif
479 /* thread_lock() performs spinlock_enter(). */
480 KASSERT(td->td_critnest == 1 || KERNEL_PANICKED(),
481 ("mi_switch: switch in a critical section"));
482 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
483 ("mi_switch: switch must be voluntary or involuntary"));
484 KASSERT((flags & SW_TYPE_MASK) != 0,
485 ("mi_switch: a switch reason (type) must be specified"));
486 KASSERT((flags & SW_TYPE_MASK) < SWT_COUNT,
487 ("mi_switch: invalid switch reason %d", (flags & SW_TYPE_MASK)));
488
489 /*
490 * Don't perform context switches from the debugger.
491 */
492 if (kdb_active)
493 kdb_switch();
494 if (SCHEDULER_STOPPED())
495 return;
496 if (flags & SW_VOL) {
497 td->td_ru.ru_nvcsw++;
498 td->td_swvoltick = ticks;
499 } else {
500 td->td_ru.ru_nivcsw++;
501 td->td_swinvoltick = ticks;
502 }
503 #ifdef SCHED_STATS
504 SCHED_STAT_INC(sched_switch_stats[flags & SW_TYPE_MASK]);
505 #endif
506 /*
507 * Compute the amount of time during which the current
508 * thread was running, and add that to its total so far.
509 */
510 new_switchtime = cpu_ticks();
511 runtime = new_switchtime - PCPU_GET(switchtime);
512 td->td_runtime += runtime;
513 td->td_incruntime += runtime;
514 PCPU_SET(switchtime, new_switchtime);
515 td->td_generation++; /* bump preempt-detect counter */
516 VM_CNT_INC(v_swtch);
517 PCPU_SET(switchticks, ticks);
518 CTR4(KTR_PROC, "mi_switch: old thread %ld (td_sched %p, pid %ld, %s)",
519 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
520 #ifdef KDTRACE_HOOKS
521 if (SDT_PROBES_ENABLED() &&
522 ((flags & SW_PREEMPT) != 0 || ((flags & SW_INVOL) != 0 &&
523 (flags & SW_TYPE_MASK) == SWT_NEEDRESCHED)))
524 SDT_PROBE0(sched, , , preempt);
525 #endif
526 sched_switch(td, flags);
527 CTR4(KTR_PROC, "mi_switch: new thread %ld (td_sched %p, pid %ld, %s)",
528 td->td_tid, td_get_sched(td), td->td_proc->p_pid, td->td_name);
529
530 /*
531 * If the last thread was exiting, finish cleaning it up.
532 */
533 if ((td = PCPU_GET(deadthread))) {
534 PCPU_SET(deadthread, NULL);
535 thread_stash(td);
536 }
537 spinlock_exit();
538 }
539
540 /*
541 * Change thread state to be runnable, placing it on the run queue.
542 *
543 * Requires the thread lock on entry, drops on exit.
544 */
545 void
setrunnable(struct thread * td,int srqflags)546 setrunnable(struct thread *td, int srqflags)
547 {
548 THREAD_LOCK_ASSERT(td, MA_OWNED);
549 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
550 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
551
552 switch (TD_GET_STATE(td)) {
553 case TDS_RUNNING:
554 case TDS_RUNQ:
555 case TDS_INHIBITED:
556 if ((srqflags & (SRQ_HOLD | SRQ_HOLDTD)) == 0)
557 thread_unlock(td);
558 break;
559 case TDS_CAN_RUN:
560 KASSERT((td->td_flags & TDF_INMEM) != 0,
561 ("setrunnable: td %p not in mem, flags 0x%X inhibit 0x%X",
562 td, td->td_flags, td->td_inhibitors));
563 /* unlocks thread lock according to flags */
564 sched_wakeup(td, srqflags);
565 break;
566 default:
567 panic("setrunnable: state 0x%x", TD_GET_STATE(td));
568 }
569 }
570
571 /*
572 * Compute a tenex style load average of a quantity on
573 * 1, 5 and 15 minute intervals.
574 */
575 static void
loadav(void * arg)576 loadav(void *arg)
577 {
578 int i;
579 uint64_t nrun;
580 struct loadavg *avg;
581
582 nrun = (uint64_t)sched_load();
583 avg = &averunnable;
584
585 for (i = 0; i < 3; i++)
586 avg->ldavg[i] = (cexp[i] * (uint64_t)avg->ldavg[i] +
587 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
588
589 /*
590 * Schedule the next update to occur after 5 seconds, but add a
591 * random variation to avoid synchronisation with processes that
592 * run at regular intervals.
593 */
594 callout_reset_sbt(&loadav_callout,
595 SBT_1US * (4000000 + (int)(random() % 2000001)), SBT_1US,
596 loadav, NULL, C_DIRECT_EXEC | C_PREL(32));
597 }
598
599 void
ast_scheduler(struct thread * td,int tda __unused)600 ast_scheduler(struct thread *td, int tda __unused)
601 {
602 #ifdef KTRACE
603 if (KTRPOINT(td, KTR_CSW))
604 ktrcsw(1, 1, __func__);
605 #endif
606 thread_lock(td);
607 sched_prio(td, td->td_user_pri);
608 mi_switch(SW_INVOL | SWT_NEEDRESCHED);
609 #ifdef KTRACE
610 if (KTRPOINT(td, KTR_CSW))
611 ktrcsw(0, 1, __func__);
612 #endif
613 }
614
615 static void
synch_setup(void * dummy __unused)616 synch_setup(void *dummy __unused)
617 {
618 callout_init(&loadav_callout, 1);
619 ast_register(TDA_SCHED, ASTR_ASTF_REQUIRED, 0, ast_scheduler);
620
621 /* Kick off timeout driven events by calling first time. */
622 loadav(NULL);
623 }
624
625 bool
should_yield(void)626 should_yield(void)
627 {
628
629 return ((u_int)ticks - (u_int)curthread->td_swvoltick >= hogticks);
630 }
631
632 void
maybe_yield(void)633 maybe_yield(void)
634 {
635
636 if (should_yield())
637 kern_yield(PRI_USER);
638 }
639
640 void
kern_yield(int prio)641 kern_yield(int prio)
642 {
643 struct thread *td;
644
645 td = curthread;
646 DROP_GIANT();
647 thread_lock(td);
648 if (prio == PRI_USER)
649 prio = td->td_user_pri;
650 if (prio >= 0)
651 sched_prio(td, prio);
652 mi_switch(SW_VOL | SWT_RELINQUISH);
653 PICKUP_GIANT();
654 }
655
656 /*
657 * General purpose yield system call.
658 */
659 int
sys_yield(struct thread * td,struct yield_args * uap)660 sys_yield(struct thread *td, struct yield_args *uap)
661 {
662
663 thread_lock(td);
664 if (PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
665 sched_prio(td, PRI_MAX_TIMESHARE);
666 mi_switch(SW_VOL | SWT_RELINQUISH);
667 td->td_retval[0] = 0;
668 return (0);
669 }
670
671 int
sys_sched_getcpu(struct thread * td,struct sched_getcpu_args * uap)672 sys_sched_getcpu(struct thread *td, struct sched_getcpu_args *uap)
673 {
674 td->td_retval[0] = td->td_oncpu;
675 return (0);
676 }
677