FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_synch.c
1 /*-
2 * Copyright (c) 1982, 1986, 1990, 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * (c) UNIX System Laboratories, Inc.
5 * All or some portions of this file are derived from material licensed
6 * to the University of California by American Telephone and Telegraph
7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
8 * the permission of UNIX System Laboratories, Inc.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95
35 */
36
37 #include <sys/cdefs.h>
38 __FBSDID("$FreeBSD$");
39
40 #include "opt_ktrace.h"
41
42 #include <sys/param.h>
43 #include <sys/systm.h>
44 #include <sys/condvar.h>
45 #include <sys/kdb.h>
46 #include <sys/kernel.h>
47 #include <sys/ktr.h>
48 #include <sys/lock.h>
49 #include <sys/mutex.h>
50 #include <sys/proc.h>
51 #include <sys/resourcevar.h>
52 #include <sys/sched.h>
53 #include <sys/signalvar.h>
54 #include <sys/sleepqueue.h>
55 #include <sys/smp.h>
56 #include <sys/sx.h>
57 #include <sys/sysctl.h>
58 #include <sys/sysproto.h>
59 #include <sys/vmmeter.h>
60 #ifdef KTRACE
61 #include <sys/uio.h>
62 #include <sys/ktrace.h>
63 #endif
64
65 #include <machine/cpu.h>
66
67 static void synch_setup(void *dummy);
68 SYSINIT(synch_setup, SI_SUB_KICK_SCHEDULER, SI_ORDER_FIRST, synch_setup, NULL)
69
70 int hogticks;
71 int lbolt;
72 static int pause_wchan;
73
74 static struct callout loadav_callout;
75 static struct callout lbolt_callout;
76
77 struct loadavg averunnable =
78 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
79 /*
80 * Constants for averages over 1, 5, and 15 minutes
81 * when sampling at 5 second intervals.
82 */
83 static fixpt_t cexp[3] = {
84 0.9200444146293232 * FSCALE, /* exp(-1/12) */
85 0.9834714538216174 * FSCALE, /* exp(-1/60) */
86 0.9944598480048967 * FSCALE, /* exp(-1/180) */
87 };
88
89 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
90 static int fscale __unused = FSCALE;
91 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
92
93 static void loadav(void *arg);
94 static void lboltcb(void *arg);
95
96 void
97 sleepinit(void)
98 {
99
100 hogticks = (hz / 10) * 2; /* Default only. */
101 init_sleepqueues();
102 }
103
104 /*
105 * General sleep call. Suspends the current thread until a wakeup is
106 * performed on the specified identifier. The thread will then be made
107 * runnable with the specified priority. Sleeps at most timo/hz seconds
108 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
109 * before and after sleeping, else signals are not checked. Returns 0 if
110 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
111 * signal needs to be delivered, ERESTART is returned if the current system
112 * call should be restarted if possible, and EINTR is returned if the system
113 * call should be interrupted by the signal (return EINTR).
114 *
115 * The lock argument is unlocked before the caller is suspended, and
116 * re-locked before _sleep() returns. If priority includes the PDROP
117 * flag the lock is not re-locked before returning.
118 */
119 int
120 _sleep(ident, lock, priority, wmesg, timo)
121 void *ident;
122 struct lock_object *lock;
123 int priority, timo;
124 const char *wmesg;
125 {
126 struct thread *td;
127 struct proc *p;
128 struct lock_class *class;
129 int catch, flags, lock_state, pri, rval;
130 WITNESS_SAVE_DECL(lock_witness);
131
132 td = curthread;
133 p = td->td_proc;
134 #ifdef KTRACE
135 if (KTRPOINT(td, KTR_CSW))
136 ktrcsw(1, 0);
137 #endif
138 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
139 "Sleeping on \"%s\"", wmesg);
140 KASSERT(timo != 0 || mtx_owned(&Giant) || lock != NULL ||
141 ident == &lbolt, ("sleeping without a lock"));
142 KASSERT(p != NULL, ("msleep1"));
143 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
144 if (lock != NULL)
145 class = LOCK_CLASS(lock);
146 else
147 class = NULL;
148
149 if (cold) {
150 /*
151 * During autoconfiguration, just return;
152 * don't run any other threads or panic below,
153 * in case this is the idle thread and already asleep.
154 * XXX: this used to do "s = splhigh(); splx(safepri);
155 * splx(s);" to give interrupts a chance, but there is
156 * no way to give interrupts a chance now.
157 */
158 if (lock != NULL && priority & PDROP)
159 class->lc_unlock(lock);
160 return (0);
161 }
162 catch = priority & PCATCH;
163 rval = 0;
164
165 /*
166 * If we are already on a sleep queue, then remove us from that
167 * sleep queue first. We have to do this to handle recursive
168 * sleeps.
169 */
170 if (TD_ON_SLEEPQ(td))
171 sleepq_remove(td, td->td_wchan);
172
173 if (ident == &pause_wchan)
174 flags = SLEEPQ_PAUSE;
175 else
176 flags = SLEEPQ_SLEEP;
177 if (catch)
178 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, p->p_pid, p->p_comm, wmesg, ident);
183
184 DROP_GIANT();
185 if (lock != NULL && !(class->lc_flags & LC_SLEEPABLE)) {
186 WITNESS_SAVE(lock, lock_witness);
187 lock_state = class->lc_unlock(lock);
188 } else
189 /* GCC needs to follow the Yellow Brick Road */
190 lock_state = -1;
191
192 /*
193 * We put ourselves on the sleep queue and start our timeout
194 * before calling thread_suspend_check, as we could stop there,
195 * and a wakeup or a SIGCONT (or both) could occur while we were
196 * stopped without resuming us. Thus, we must be ready for sleep
197 * when cursig() is called. If the wakeup happens while we're
198 * stopped, then td will no longer be on a sleep queue upon
199 * return from cursig().
200 */
201 sleepq_add(ident, ident == &lbolt ? NULL : lock, wmesg, flags, 0);
202 if (timo)
203 sleepq_set_timeout(ident, timo);
204 if (lock != NULL && class->lc_flags & LC_SLEEPABLE) {
205 sleepq_release(ident);
206 WITNESS_SAVE(lock, lock_witness);
207 lock_state = class->lc_unlock(lock);
208 sleepq_lock(ident);
209 }
210
211 /*
212 * Adjust this thread's priority, if necessary.
213 */
214 pri = priority & PRIMASK;
215 if (pri != 0 && pri != td->td_priority) {
216 thread_lock(td);
217 sched_prio(td, pri);
218 thread_unlock(td);
219 }
220
221 if (timo && catch)
222 rval = sleepq_timedwait_sig(ident);
223 else if (timo)
224 rval = sleepq_timedwait(ident);
225 else if (catch)
226 rval = sleepq_wait_sig(ident);
227 else {
228 sleepq_wait(ident);
229 rval = 0;
230 }
231 #ifdef KTRACE
232 if (KTRPOINT(td, KTR_CSW))
233 ktrcsw(0, 0);
234 #endif
235 PICKUP_GIANT();
236 if (lock != NULL && !(priority & PDROP)) {
237 class->lc_lock(lock, lock_state);
238 WITNESS_RESTORE(lock, lock_witness);
239 }
240 return (rval);
241 }
242
243 int
244 msleep_spin(ident, mtx, wmesg, timo)
245 void *ident;
246 struct mtx *mtx;
247 const char *wmesg;
248 int timo;
249 {
250 struct thread *td;
251 struct proc *p;
252 int rval;
253 WITNESS_SAVE_DECL(mtx);
254
255 td = curthread;
256 p = td->td_proc;
257 KASSERT(mtx != NULL, ("sleeping without a mutex"));
258 KASSERT(p != NULL, ("msleep1"));
259 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
260
261 if (cold) {
262 /*
263 * During autoconfiguration, just return;
264 * don't run any other threads or panic below,
265 * in case this is the idle thread and already asleep.
266 * XXX: this used to do "s = splhigh(); splx(safepri);
267 * splx(s);" to give interrupts a chance, but there is
268 * no way to give interrupts a chance now.
269 */
270 return (0);
271 }
272
273 sleepq_lock(ident);
274 CTR5(KTR_PROC, "msleep_spin: thread %ld (pid %ld, %s) on %s (%p)",
275 td->td_tid, p->p_pid, p->p_comm, wmesg, ident);
276
277 DROP_GIANT();
278 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
279 WITNESS_SAVE(&mtx->lock_object, mtx);
280 mtx_unlock_spin(mtx);
281
282 /*
283 * We put ourselves on the sleep queue and start our timeout.
284 */
285 sleepq_add(ident, &mtx->lock_object, wmesg, SLEEPQ_SLEEP, 0);
286 if (timo)
287 sleepq_set_timeout(ident, timo);
288
289 /*
290 * Can't call ktrace with any spin locks held so it can lock the
291 * ktrace_mtx lock, and WITNESS_WARN considers it an error to hold
292 * any spin lock. Thus, we have to drop the sleepq spin lock while
293 * we handle those requests. This is safe since we have placed our
294 * thread on the sleep queue already.
295 */
296 #ifdef KTRACE
297 if (KTRPOINT(td, KTR_CSW)) {
298 sleepq_release(ident);
299 ktrcsw(1, 0);
300 sleepq_lock(ident);
301 }
302 #endif
303 #ifdef WITNESS
304 sleepq_release(ident);
305 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "Sleeping on \"%s\"",
306 wmesg);
307 sleepq_lock(ident);
308 #endif
309 if (timo)
310 rval = sleepq_timedwait(ident);
311 else {
312 sleepq_wait(ident);
313 rval = 0;
314 }
315 #ifdef KTRACE
316 if (KTRPOINT(td, KTR_CSW))
317 ktrcsw(0, 0);
318 #endif
319 PICKUP_GIANT();
320 mtx_lock_spin(mtx);
321 WITNESS_RESTORE(&mtx->lock_object, mtx);
322 return (rval);
323 }
324
325 /*
326 * pause() is like tsleep() except that the intention is to not be
327 * explicitly woken up by another thread. Instead, the current thread
328 * simply wishes to sleep until the timeout expires. It is
329 * implemented using a dummy wait channel.
330 */
331 int
332 pause(wmesg, timo)
333 const char *wmesg;
334 int timo;
335 {
336
337 KASSERT(timo != 0, ("pause: timeout required"));
338 return (tsleep(&pause_wchan, 0, wmesg, timo));
339 }
340
341 /*
342 * Make all threads sleeping on the specified identifier runnable.
343 */
344 void
345 wakeup(ident)
346 register void *ident;
347 {
348
349 sleepq_lock(ident);
350 sleepq_broadcast(ident, SLEEPQ_SLEEP, -1, 0);
351 }
352
353 /*
354 * Make a thread sleeping on the specified identifier runnable.
355 * May wake more than one thread if a target thread is currently
356 * swapped out.
357 */
358 void
359 wakeup_one(ident)
360 register void *ident;
361 {
362
363 sleepq_lock(ident);
364 sleepq_signal(ident, SLEEPQ_SLEEP, -1, 0);
365 sleepq_release(ident);
366 }
367
368 /*
369 * The machine independent parts of context switching.
370 */
371 void
372 mi_switch(int flags, struct thread *newtd)
373 {
374 uint64_t new_switchtime;
375 struct thread *td;
376 struct proc *p;
377
378 td = curthread; /* XXX */
379 THREAD_LOCK_ASSERT(td, MA_OWNED | MA_NOTRECURSED);
380 p = td->td_proc; /* XXX */
381 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
382 #ifdef INVARIANTS
383 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
384 mtx_assert(&Giant, MA_NOTOWNED);
385 #endif
386 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
387 (td->td_owepreempt) && (flags & SW_INVOL) != 0 &&
388 newtd == NULL) || panicstr,
389 ("mi_switch: switch in a critical section"));
390 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
391 ("mi_switch: switch must be voluntary or involuntary"));
392 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
393
394 /*
395 * Don't perform context switches from the debugger.
396 */
397 if (kdb_active) {
398 thread_unlock(td);
399 kdb_backtrace();
400 kdb_reenter();
401 panic("%s: did not reenter debugger", __func__);
402 }
403 if (flags & SW_VOL)
404 td->td_ru.ru_nvcsw++;
405 else
406 td->td_ru.ru_nivcsw++;
407 /*
408 * Compute the amount of time during which the current
409 * thread was running, and add that to its total so far.
410 */
411 new_switchtime = cpu_ticks();
412 td->td_runtime += new_switchtime - PCPU_GET(switchtime);
413 PCPU_SET(switchtime, new_switchtime);
414 td->td_generation++; /* bump preempt-detect counter */
415 PCPU_INC(cnt.v_swtch);
416 PCPU_SET(switchticks, ticks);
417 CTR4(KTR_PROC, "mi_switch: old thread %ld (kse %p, pid %ld, %s)",
418 td->td_tid, td->td_sched, p->p_pid, p->p_comm);
419 #if (KTR_COMPILE & KTR_SCHED) != 0
420 if (TD_IS_IDLETHREAD(td))
421 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
422 td, td->td_proc->p_comm, td->td_priority);
423 else if (newtd != NULL)
424 CTR5(KTR_SCHED,
425 "mi_switch: %p(%s) prio %d preempted by %p(%s)",
426 td, td->td_proc->p_comm, td->td_priority, newtd,
427 newtd->td_proc->p_comm);
428 else
429 CTR6(KTR_SCHED,
430 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
431 td, td->td_proc->p_comm, td->td_priority,
432 td->td_inhibitors, td->td_wmesg, td->td_lockname);
433 #endif
434 /*
435 * We call thread_switchout after the KTR_SCHED prints above so kse
436 * selecting a new thread to run does not show up as a preemption.
437 */
438 #ifdef KSE
439 if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
440 newtd = thread_switchout(td, flags, newtd);
441 #endif
442 sched_switch(td, newtd, flags);
443 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
444 td, td->td_proc->p_comm, td->td_priority);
445
446 CTR4(KTR_PROC, "mi_switch: new thread %ld (kse %p, pid %ld, %s)",
447 td->td_tid, td->td_sched, p->p_pid, p->p_comm);
448
449 /*
450 * If the last thread was exiting, finish cleaning it up.
451 */
452 if ((td = PCPU_GET(deadthread))) {
453 PCPU_SET(deadthread, NULL);
454 thread_stash(td);
455 }
456 }
457
458 /*
459 * Change process state to be runnable,
460 * placing it on the run queue if it is in memory,
461 * and awakening the swapper if it isn't in memory.
462 */
463 void
464 setrunnable(struct thread *td)
465 {
466
467 THREAD_LOCK_ASSERT(td, MA_OWNED);
468 KASSERT(td->td_proc->p_state != PRS_ZOMBIE,
469 ("setrunnable: pid %d is a zombie", td->td_proc->p_pid));
470 switch (td->td_state) {
471 case TDS_RUNNING:
472 case TDS_RUNQ:
473 return;
474 case TDS_INHIBITED:
475 /*
476 * If we are only inhibited because we are swapped out
477 * then arange to swap in this process. Otherwise just return.
478 */
479 if (td->td_inhibitors != TDI_SWAPPED)
480 return;
481 /* XXX: intentional fall-through ? */
482 case TDS_CAN_RUN:
483 break;
484 default:
485 printf("state is 0x%x", td->td_state);
486 panic("setrunnable(2)");
487 }
488 if ((td->td_flags & TDF_INMEM) == 0) {
489 if ((td->td_flags & TDF_SWAPINREQ) == 0) {
490 td->td_flags |= TDF_SWAPINREQ;
491 /*
492 * due to a LOR between the thread lock and
493 * the sleepqueue chain locks, use
494 * lower level scheduling functions.
495 */
496 kick_proc0();
497 }
498 } else
499 sched_wakeup(td);
500 }
501
502 /*
503 * Compute a tenex style load average of a quantity on
504 * 1, 5 and 15 minute intervals.
505 * XXXKSE Needs complete rewrite when correct info is available.
506 * Completely Bogus.. only works with 1:1 (but compiles ok now :-)
507 */
508 static void
509 loadav(void *arg)
510 {
511 int i, nrun;
512 struct loadavg *avg;
513
514 nrun = sched_load();
515 avg = &averunnable;
516
517 for (i = 0; i < 3; i++)
518 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
519 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
520
521 /*
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.
525 */
526 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
527 loadav, NULL);
528 }
529
530 static void
531 lboltcb(void *arg)
532 {
533 wakeup(&lbolt);
534 callout_reset(&lbolt_callout, hz, lboltcb, NULL);
535 }
536
537 /* ARGSUSED */
538 static void
539 synch_setup(dummy)
540 void *dummy;
541 {
542 callout_init(&loadav_callout, CALLOUT_MPSAFE);
543 callout_init(&lbolt_callout, CALLOUT_MPSAFE);
544
545 /* Kick off timeout driven events by calling first time. */
546 loadav(NULL);
547 lboltcb(NULL);
548 }
549
550 /*
551 * General purpose yield system call.
552 */
553 int
554 yield(struct thread *td, struct yield_args *uap)
555 {
556
557 thread_lock(td);
558 sched_prio(td, PRI_MAX_TIMESHARE);
559 mi_switch(SW_VOL, NULL);
560 thread_unlock(td);
561 td->td_retval[0] = 0;
562 return (0);
563 }
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