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: src/sys/kern/kern_synch.c,v 1.257.2.9 2005/12/05 20:14:56 jhb Exp $");
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
73 static struct callout loadav_callout;
74 static struct callout lbolt_callout;
75
76 struct loadavg averunnable =
77 { {0, 0, 0}, FSCALE }; /* load average, of runnable procs */
78 /*
79 * Constants for averages over 1, 5, and 15 minutes
80 * when sampling at 5 second intervals.
81 */
82 static fixpt_t cexp[3] = {
83 0.9200444146293232 * FSCALE, /* exp(-1/12) */
84 0.9834714538216174 * FSCALE, /* exp(-1/60) */
85 0.9944598480048967 * FSCALE, /* exp(-1/180) */
86 };
87
88 /* kernel uses `FSCALE', userland (SHOULD) use kern.fscale */
89 static int fscale __unused = FSCALE;
90 SYSCTL_INT(_kern, OID_AUTO, fscale, CTLFLAG_RD, 0, FSCALE, "");
91
92 static void loadav(void *arg);
93 static void lboltcb(void *arg);
94
95 void
96 sleepinit(void)
97 {
98
99 hogticks = (hz / 10) * 2; /* Default only. */
100 init_sleepqueues();
101 }
102
103 /*
104 * General sleep call. Suspends the current process until a wakeup is
105 * performed on the specified identifier. The process will then be made
106 * runnable with the specified priority. Sleeps at most timo/hz seconds
107 * (0 means no timeout). If pri includes PCATCH flag, signals are checked
108 * before and after sleeping, else signals are not checked. Returns 0 if
109 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
110 * signal needs to be delivered, ERESTART is returned if the current system
111 * call should be restarted if possible, and EINTR is returned if the system
112 * call should be interrupted by the signal (return EINTR).
113 *
114 * The mutex argument is exited before the caller is suspended, and
115 * entered before msleep returns. If priority includes the PDROP
116 * flag the mutex is not entered before returning.
117 */
118 int
119 msleep(ident, mtx, priority, wmesg, timo)
120 void *ident;
121 struct mtx *mtx;
122 int priority, timo;
123 const char *wmesg;
124 {
125 struct sleepqueue *sq;
126 struct thread *td;
127 struct proc *p;
128 int catch, rval, sig, flags;
129 WITNESS_SAVE_DECL(mtx);
130
131 td = curthread;
132 p = td->td_proc;
133 #ifdef KTRACE
134 if (KTRPOINT(td, KTR_CSW))
135 ktrcsw(1, 0);
136 #endif
137 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, mtx == NULL ? NULL :
138 &mtx->mtx_object, "Sleeping on \"%s\"", wmesg);
139 KASSERT(timo != 0 || mtx_owned(&Giant) || mtx != NULL,
140 ("sleeping without a mutex"));
141 KASSERT(p != NULL, ("msleep1"));
142 KASSERT(ident != NULL && TD_IS_RUNNING(td), ("msleep"));
143
144 if (cold) {
145 /*
146 * During autoconfiguration, just return;
147 * don't run any other threads or panic below,
148 * in case this is the idle thread and already asleep.
149 * XXX: this used to do "s = splhigh(); splx(safepri);
150 * splx(s);" to give interrupts a chance, but there is
151 * no way to give interrupts a chance now.
152 */
153 if (mtx != NULL && priority & PDROP)
154 mtx_unlock(mtx);
155 return (0);
156 }
157 catch = priority & PCATCH;
158 rval = 0;
159
160 /*
161 * If we are already on a sleep queue, then remove us from that
162 * sleep queue first. We have to do this to handle recursive
163 * sleeps.
164 */
165 if (TD_ON_SLEEPQ(td))
166 sleepq_remove(td, td->td_wchan);
167
168 sq = sleepq_lookup(ident);
169 if (catch) {
170 /*
171 * Don't bother sleeping if we are exiting and not the exiting
172 * thread or if our thread is marked as interrupted.
173 */
174 mtx_lock_spin(&sched_lock);
175 rval = thread_sleep_check(td);
176 mtx_unlock_spin(&sched_lock);
177 if (rval != 0) {
178 sleepq_release(ident);
179 return (rval);
180 }
181 }
182 CTR5(KTR_PROC, "msleep: thread %p (pid %ld, %s) on %s (%p)",
183 (void *)td, (long)p->p_pid, p->p_comm, wmesg, ident);
184
185 DROP_GIANT();
186 if (mtx != NULL) {
187 mtx_assert(mtx, MA_OWNED | MA_NOTRECURSED);
188 WITNESS_SAVE(&mtx->mtx_object, mtx);
189 mtx_unlock(mtx);
190 }
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 flags = SLEEPQ_MSLEEP;
202 if (catch)
203 flags |= SLEEPQ_INTERRUPTIBLE;
204 sleepq_add(sq, ident, mtx, wmesg, flags);
205 if (timo)
206 sleepq_set_timeout(ident, timo);
207 if (catch) {
208 sig = sleepq_catch_signals(ident);
209 } else
210 sig = 0;
211
212 /*
213 * Adjust this thread's priority.
214 *
215 * XXX: do we need to save priority in td_base_pri?
216 */
217 mtx_lock_spin(&sched_lock);
218 sched_prio(td, priority & PRIMASK);
219 mtx_unlock_spin(&sched_lock);
220
221 if (timo && catch)
222 rval = sleepq_timedwait_sig(ident, sig != 0);
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 if (rval == 0 && catch)
232 rval = sleepq_calc_signal_retval(sig);
233 #ifdef KTRACE
234 if (KTRPOINT(td, KTR_CSW))
235 ktrcsw(0, 0);
236 #endif
237 PICKUP_GIANT();
238 if (mtx != NULL && !(priority & PDROP)) {
239 mtx_lock(mtx);
240 WITNESS_RESTORE(&mtx->mtx_object, mtx);
241 }
242 return (rval);
243 }
244
245 /*
246 * Make all threads sleeping on the specified identifier runnable.
247 */
248 void
249 wakeup(ident)
250 register void *ident;
251 {
252
253 sleepq_broadcast(ident, SLEEPQ_MSLEEP, -1);
254 }
255
256 /*
257 * Make a thread sleeping on the specified identifier runnable.
258 * May wake more than one thread if a target thread is currently
259 * swapped out.
260 */
261 void
262 wakeup_one(ident)
263 register void *ident;
264 {
265
266 sleepq_signal(ident, SLEEPQ_MSLEEP, -1);
267 }
268
269 /*
270 * The machine independent parts of context switching.
271 */
272 void
273 mi_switch(int flags, struct thread *newtd)
274 {
275 struct bintime new_switchtime;
276 struct thread *td;
277 struct proc *p;
278
279 mtx_assert(&sched_lock, MA_OWNED | MA_NOTRECURSED);
280 td = curthread; /* XXX */
281 p = td->td_proc; /* XXX */
282 KASSERT(!TD_ON_RUNQ(td), ("mi_switch: called by old code"));
283 #ifdef INVARIANTS
284 if (!TD_ON_LOCK(td) && !TD_IS_RUNNING(td))
285 mtx_assert(&Giant, MA_NOTOWNED);
286 #endif
287 KASSERT(td->td_critnest == 1 || (td->td_critnest == 2 &&
288 (td->td_pflags & TDP_OWEPREEMPT) != 0 && (flags & SW_INVOL) != 0 &&
289 newtd == NULL),
290 ("mi_switch: switch in a critical section"));
291 KASSERT((flags & (SW_INVOL | SW_VOL)) != 0,
292 ("mi_switch: switch must be voluntary or involuntary"));
293 KASSERT(newtd != curthread, ("mi_switch: preempting back to ourself"));
294
295 if (flags & SW_VOL)
296 p->p_stats->p_ru.ru_nvcsw++;
297 else
298 p->p_stats->p_ru.ru_nivcsw++;
299
300 /*
301 * Compute the amount of time during which the current
302 * process was running, and add that to its total so far.
303 */
304 binuptime(&new_switchtime);
305 bintime_add(&p->p_runtime, &new_switchtime);
306 bintime_sub(&p->p_runtime, PCPU_PTR(switchtime));
307
308 td->td_generation++; /* bump preempt-detect counter */
309
310 /*
311 * Don't perform context switches from the debugger.
312 */
313 if (kdb_active) {
314 mtx_unlock_spin(&sched_lock);
315 kdb_backtrace();
316 kdb_reenter();
317 panic("%s: did not reenter debugger", __func__);
318 }
319
320 /*
321 * Check if the process exceeds its cpu resource allocation. If
322 * it reaches the max, arrange to kill the process in ast().
323 */
324 if (p->p_cpulimit != RLIM_INFINITY &&
325 p->p_runtime.sec >= p->p_cpulimit) {
326 p->p_sflag |= PS_XCPU;
327 td->td_flags |= TDF_ASTPENDING;
328 }
329
330 /*
331 * Finish up stats for outgoing thread.
332 */
333 cnt.v_swtch++;
334 PCPU_SET(switchtime, new_switchtime);
335 PCPU_SET(switchticks, ticks);
336 CTR4(KTR_PROC, "mi_switch: old thread %p (kse %p, pid %ld, %s)",
337 (void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
338 if ((flags & SW_VOL) && (td->td_proc->p_flag & P_SA))
339 newtd = thread_switchout(td, flags, newtd);
340 #if (KTR_COMPILE & KTR_SCHED) != 0
341 if (td == PCPU_GET(idlethread))
342 CTR3(KTR_SCHED, "mi_switch: %p(%s) prio %d idle",
343 td, td->td_proc->p_comm, td->td_priority);
344 else if (newtd != NULL)
345 CTR5(KTR_SCHED,
346 "mi_switch: %p(%s) prio %d preempted by %p(%s)",
347 td, td->td_proc->p_comm, td->td_priority, newtd,
348 newtd->td_proc->p_comm);
349 else
350 CTR6(KTR_SCHED,
351 "mi_switch: %p(%s) prio %d inhibit %d wmesg %s lock %s",
352 td, td->td_proc->p_comm, td->td_priority,
353 td->td_inhibitors, td->td_wmesg, td->td_lockname);
354 #endif
355 sched_switch(td, newtd, flags);
356 CTR3(KTR_SCHED, "mi_switch: running %p(%s) prio %d",
357 td, td->td_proc->p_comm, td->td_priority);
358
359 CTR4(KTR_PROC, "mi_switch: new thread %p (kse %p, pid %ld, %s)",
360 (void *)td, td->td_sched, (long)p->p_pid, p->p_comm);
361
362 /*
363 * If the last thread was exiting, finish cleaning it up.
364 */
365 if ((td = PCPU_GET(deadthread))) {
366 PCPU_SET(deadthread, NULL);
367 thread_stash(td);
368 }
369 }
370
371 /*
372 * Change process state to be runnable,
373 * placing it on the run queue if it is in memory,
374 * and awakening the swapper if it isn't in memory.
375 */
376 void
377 setrunnable(struct thread *td)
378 {
379 struct proc *p;
380
381 p = td->td_proc;
382 mtx_assert(&sched_lock, MA_OWNED);
383 switch (p->p_state) {
384 case PRS_ZOMBIE:
385 panic("setrunnable(1)");
386 default:
387 break;
388 }
389 switch (td->td_state) {
390 case TDS_RUNNING:
391 case TDS_RUNQ:
392 return;
393 case TDS_INHIBITED:
394 /*
395 * If we are only inhibited because we are swapped out
396 * then arange to swap in this process. Otherwise just return.
397 */
398 if (td->td_inhibitors != TDI_SWAPPED)
399 return;
400 /* XXX: intentional fall-through ? */
401 case TDS_CAN_RUN:
402 break;
403 default:
404 printf("state is 0x%x", td->td_state);
405 panic("setrunnable(2)");
406 }
407 if ((p->p_sflag & PS_INMEM) == 0) {
408 if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
409 p->p_sflag |= PS_SWAPINREQ;
410 /*
411 * due to a LOR between sched_lock and
412 * the sleepqueue chain locks, delay
413 * wakeup proc0 until thread leaves
414 * critical region.
415 */
416 curthread->td_pflags |= TDP_WAKEPROC0;
417 }
418 } else
419 sched_wakeup(td);
420 }
421
422 /*
423 * Compute a tenex style load average of a quantity on
424 * 1, 5 and 15 minute intervals.
425 * XXXKSE Needs complete rewrite when correct info is available.
426 * Completely Bogus.. only works with 1:1 (but compiles ok now :-)
427 */
428 static void
429 loadav(void *arg)
430 {
431 int i, nrun;
432 struct loadavg *avg;
433
434 nrun = sched_load();
435 avg = &averunnable;
436
437 for (i = 0; i < 3; i++)
438 avg->ldavg[i] = (cexp[i] * avg->ldavg[i] +
439 nrun * FSCALE * (FSCALE - cexp[i])) >> FSHIFT;
440
441 /*
442 * Schedule the next update to occur after 5 seconds, but add a
443 * random variation to avoid synchronisation with processes that
444 * run at regular intervals.
445 */
446 callout_reset(&loadav_callout, hz * 4 + (int)(random() % (hz * 2 + 1)),
447 loadav, NULL);
448 }
449
450 static void
451 lboltcb(void *arg)
452 {
453 wakeup(&lbolt);
454 callout_reset(&lbolt_callout, hz, lboltcb, NULL);
455 }
456
457 /* ARGSUSED */
458 static void
459 synch_setup(dummy)
460 void *dummy;
461 {
462 callout_init(&loadav_callout, CALLOUT_MPSAFE);
463 callout_init(&lbolt_callout, CALLOUT_MPSAFE);
464
465 /* Kick off timeout driven events by calling first time. */
466 loadav(NULL);
467 lboltcb(NULL);
468 }
469
470 /*
471 * General purpose yield system call
472 */
473 int
474 yield(struct thread *td, struct yield_args *uap)
475 {
476 struct ksegrp *kg;
477
478 kg = td->td_ksegrp;
479 mtx_assert(&Giant, MA_NOTOWNED);
480 mtx_lock_spin(&sched_lock);
481 sched_prio(td, PRI_MAX_TIMESHARE);
482 mi_switch(SW_VOL, NULL);
483 mtx_unlock_spin(&sched_lock);
484 td->td_retval[0] = 0;
485 return (0);
486 }
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