1 /*-
2 * Copyright (c) 2000 Jake Burkholder <jake@freebsd.org>.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 #include <sys/cdefs.h>
28 __FBSDID("$FreeBSD: releng/8.4/sys/kern/kern_condvar.c 237720 2012-06-28 18:38:50Z jhb $");
29
30 #include "opt_ktrace.h"
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/lock.h>
35 #include <sys/mutex.h>
36 #include <sys/proc.h>
37 #include <sys/kernel.h>
38 #include <sys/ktr.h>
39 #include <sys/condvar.h>
40 #include <sys/sched.h>
41 #include <sys/signalvar.h>
42 #include <sys/sleepqueue.h>
43 #include <sys/resourcevar.h>
44 #ifdef KTRACE
45 #include <sys/uio.h>
46 #include <sys/ktrace.h>
47 #endif
48
49 /*
50 * Common sanity checks for cv_wait* functions.
51 */
52 #define CV_ASSERT(cvp, lock, td) do { \
53 KASSERT((td) != NULL, ("%s: curthread NULL", __func__)); \
54 KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__)); \
55 KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__)); \
56 KASSERT((lock) != NULL, ("%s: lock NULL", __func__)); \
57 } while (0)
58
59 /*
60 * Initialize a condition variable. Must be called before use.
61 */
62 void
63 cv_init(struct cv *cvp, const char *desc)
64 {
65
66 cvp->cv_description = desc;
67 cvp->cv_waiters = 0;
68 }
69
70 /*
71 * Destroy a condition variable. The condition variable must be re-initialized
72 * in order to be re-used.
73 */
74 void
75 cv_destroy(struct cv *cvp)
76 {
77 #ifdef INVARIANTS
78 struct sleepqueue *sq;
79
80 sleepq_lock(cvp);
81 sq = sleepq_lookup(cvp);
82 sleepq_release(cvp);
83 KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__));
84 #endif
85 }
86
87 /*
88 * Wait on a condition variable. The current thread is placed on the condition
89 * variable's wait queue and suspended. A cv_signal or cv_broadcast on the same
90 * condition variable will resume the thread. The mutex is released before
91 * sleeping and will be held on return. It is recommended that the mutex be
92 * held when cv_signal or cv_broadcast are called.
93 */
94 void
95 _cv_wait(struct cv *cvp, struct lock_object *lock)
96 {
97 WITNESS_SAVE_DECL(lock_witness);
98 struct lock_class *class;
99 struct thread *td;
100 int lock_state;
101
102 td = curthread;
103 lock_state = 0;
104 #ifdef KTRACE
105 if (KTRPOINT(td, KTR_CSW))
106 ktrcsw(1, 0, cv_wmesg(cvp));
107 #endif
108 CV_ASSERT(cvp, lock, td);
109 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
110 "Waiting on \"%s\"", cvp->cv_description);
111 class = LOCK_CLASS(lock);
112
113 if (cold || panicstr) {
114 /*
115 * During autoconfiguration, just give interrupts
116 * a chance, then just return. Don't run any other
117 * thread or panic below, in case this is the idle
118 * process and already asleep.
119 */
120 return;
121 }
122
123 sleepq_lock(cvp);
124
125 cvp->cv_waiters++;
126 if (lock == &Giant.lock_object)
127 mtx_assert(&Giant, MA_OWNED);
128 DROP_GIANT();
129
130 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
131 if (lock != &Giant.lock_object) {
132 if (class->lc_flags & LC_SLEEPABLE)
133 sleepq_release(cvp);
134 WITNESS_SAVE(lock, lock_witness);
135 lock_state = class->lc_unlock(lock);
136 if (class->lc_flags & LC_SLEEPABLE)
137 sleepq_lock(cvp);
138 }
139 sleepq_wait(cvp, 0);
140
141 #ifdef KTRACE
142 if (KTRPOINT(td, KTR_CSW))
143 ktrcsw(0, 0, cv_wmesg(cvp));
144 #endif
145 PICKUP_GIANT();
146 if (lock != &Giant.lock_object) {
147 class->lc_lock(lock, lock_state);
148 WITNESS_RESTORE(lock, lock_witness);
149 }
150 }
151
152 /*
153 * Wait on a condition variable. This function differs from cv_wait by
154 * not aquiring the mutex after condition variable was signaled.
155 */
156 void
157 _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
158 {
159 struct lock_class *class;
160 struct thread *td;
161
162 td = curthread;
163 #ifdef KTRACE
164 if (KTRPOINT(td, KTR_CSW))
165 ktrcsw(1, 0, cv_wmesg(cvp));
166 #endif
167 CV_ASSERT(cvp, lock, td);
168 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
169 "Waiting on \"%s\"", cvp->cv_description);
170 KASSERT(lock != &Giant.lock_object,
171 ("cv_wait_unlock cannot be used with Giant"));
172 class = LOCK_CLASS(lock);
173
174 if (cold || panicstr) {
175 /*
176 * During autoconfiguration, just give interrupts
177 * a chance, then just return. Don't run any other
178 * thread or panic below, in case this is the idle
179 * process and already asleep.
180 */
181 class->lc_unlock(lock);
182 return;
183 }
184
185 sleepq_lock(cvp);
186
187 cvp->cv_waiters++;
188 DROP_GIANT();
189
190 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
191 if (class->lc_flags & LC_SLEEPABLE)
192 sleepq_release(cvp);
193 class->lc_unlock(lock);
194 if (class->lc_flags & LC_SLEEPABLE)
195 sleepq_lock(cvp);
196 sleepq_wait(cvp, 0);
197
198 #ifdef KTRACE
199 if (KTRPOINT(td, KTR_CSW))
200 ktrcsw(0, 0, cv_wmesg(cvp));
201 #endif
202 PICKUP_GIANT();
203 }
204
205 /*
206 * Wait on a condition variable, allowing interruption by signals. Return 0 if
207 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
208 * a signal was caught. If ERESTART is returned the system call should be
209 * restarted if possible.
210 */
211 int
212 _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
213 {
214 WITNESS_SAVE_DECL(lock_witness);
215 struct lock_class *class;
216 struct thread *td;
217 int lock_state, rval;
218
219 td = curthread;
220 lock_state = 0;
221 #ifdef KTRACE
222 if (KTRPOINT(td, KTR_CSW))
223 ktrcsw(1, 0, cv_wmesg(cvp));
224 #endif
225 CV_ASSERT(cvp, lock, td);
226 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
227 "Waiting on \"%s\"", cvp->cv_description);
228 class = LOCK_CLASS(lock);
229
230 if (cold || panicstr) {
231 /*
232 * After a panic, or during autoconfiguration, just give
233 * interrupts a chance, then just return; don't run any other
234 * procs or panic below, in case this is the idle process and
235 * already asleep.
236 */
237 return (0);
238 }
239
240 sleepq_lock(cvp);
241
242 cvp->cv_waiters++;
243 if (lock == &Giant.lock_object)
244 mtx_assert(&Giant, MA_OWNED);
245 DROP_GIANT();
246
247 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
248 SLEEPQ_INTERRUPTIBLE, 0);
249 if (lock != &Giant.lock_object) {
250 if (class->lc_flags & LC_SLEEPABLE)
251 sleepq_release(cvp);
252 WITNESS_SAVE(lock, lock_witness);
253 lock_state = class->lc_unlock(lock);
254 if (class->lc_flags & LC_SLEEPABLE)
255 sleepq_lock(cvp);
256 }
257 rval = sleepq_wait_sig(cvp, 0);
258
259 #ifdef KTRACE
260 if (KTRPOINT(td, KTR_CSW))
261 ktrcsw(0, 0, cv_wmesg(cvp));
262 #endif
263 PICKUP_GIANT();
264 if (lock != &Giant.lock_object) {
265 class->lc_lock(lock, lock_state);
266 WITNESS_RESTORE(lock, lock_witness);
267 }
268
269 return (rval);
270 }
271
272 /*
273 * Wait on a condition variable for at most timo/hz seconds. Returns 0 if the
274 * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout
275 * expires.
276 */
277 int
278 _cv_timedwait(struct cv *cvp, struct lock_object *lock, int timo)
279 {
280 WITNESS_SAVE_DECL(lock_witness);
281 struct lock_class *class;
282 struct thread *td;
283 int lock_state, rval;
284
285 td = curthread;
286 lock_state = 0;
287 #ifdef KTRACE
288 if (KTRPOINT(td, KTR_CSW))
289 ktrcsw(1, 0, cv_wmesg(cvp));
290 #endif
291 CV_ASSERT(cvp, lock, td);
292 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
293 "Waiting on \"%s\"", cvp->cv_description);
294 class = LOCK_CLASS(lock);
295
296 if (cold || panicstr) {
297 /*
298 * After a panic, or during autoconfiguration, just give
299 * interrupts a chance, then just return; don't run any other
300 * thread or panic below, in case this is the idle process and
301 * already asleep.
302 */
303 return 0;
304 }
305
306 sleepq_lock(cvp);
307
308 cvp->cv_waiters++;
309 if (lock == &Giant.lock_object)
310 mtx_assert(&Giant, MA_OWNED);
311 DROP_GIANT();
312
313 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
314 sleepq_set_timeout(cvp, timo);
315 if (lock != &Giant.lock_object) {
316 if (class->lc_flags & LC_SLEEPABLE)
317 sleepq_release(cvp);
318 WITNESS_SAVE(lock, lock_witness);
319 lock_state = class->lc_unlock(lock);
320 if (class->lc_flags & LC_SLEEPABLE)
321 sleepq_lock(cvp);
322 }
323 rval = sleepq_timedwait(cvp, 0);
324
325 #ifdef KTRACE
326 if (KTRPOINT(td, KTR_CSW))
327 ktrcsw(0, 0, cv_wmesg(cvp));
328 #endif
329 PICKUP_GIANT();
330 if (lock != &Giant.lock_object) {
331 class->lc_lock(lock, lock_state);
332 WITNESS_RESTORE(lock, lock_witness);
333 }
334
335 return (rval);
336 }
337
338 /*
339 * Wait on a condition variable for at most timo/hz seconds, allowing
340 * interruption by signals. Returns 0 if the thread was resumed by cv_signal
341 * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if
342 * a signal was caught.
343 */
344 int
345 _cv_timedwait_sig(struct cv *cvp, struct lock_object *lock, int timo)
346 {
347 WITNESS_SAVE_DECL(lock_witness);
348 struct lock_class *class;
349 struct thread *td;
350 int lock_state, rval;
351
352 td = curthread;
353 lock_state = 0;
354 #ifdef KTRACE
355 if (KTRPOINT(td, KTR_CSW))
356 ktrcsw(1, 0, cv_wmesg(cvp));
357 #endif
358 CV_ASSERT(cvp, lock, td);
359 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
360 "Waiting on \"%s\"", cvp->cv_description);
361 class = LOCK_CLASS(lock);
362
363 if (cold || panicstr) {
364 /*
365 * After a panic, or during autoconfiguration, just give
366 * interrupts a chance, then just return; don't run any other
367 * thread or panic below, in case this is the idle process and
368 * already asleep.
369 */
370 return 0;
371 }
372
373 sleepq_lock(cvp);
374
375 cvp->cv_waiters++;
376 if (lock == &Giant.lock_object)
377 mtx_assert(&Giant, MA_OWNED);
378 DROP_GIANT();
379
380 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
381 SLEEPQ_INTERRUPTIBLE, 0);
382 sleepq_set_timeout(cvp, timo);
383 if (lock != &Giant.lock_object) {
384 if (class->lc_flags & LC_SLEEPABLE)
385 sleepq_release(cvp);
386 WITNESS_SAVE(lock, lock_witness);
387 lock_state = class->lc_unlock(lock);
388 if (class->lc_flags & LC_SLEEPABLE)
389 sleepq_lock(cvp);
390 }
391 rval = sleepq_timedwait_sig(cvp, 0);
392
393 #ifdef KTRACE
394 if (KTRPOINT(td, KTR_CSW))
395 ktrcsw(0, 0, cv_wmesg(cvp));
396 #endif
397 PICKUP_GIANT();
398 if (lock != &Giant.lock_object) {
399 class->lc_lock(lock, lock_state);
400 WITNESS_RESTORE(lock, lock_witness);
401 }
402
403 return (rval);
404 }
405
406 /*
407 * Signal a condition variable, wakes up one waiting thread. Will also wakeup
408 * the swapper if the process is not in memory, so that it can bring the
409 * sleeping process in. Note that this may also result in additional threads
410 * being made runnable. Should be called with the same mutex as was passed to
411 * cv_wait held.
412 */
413 void
414 cv_signal(struct cv *cvp)
415 {
416 int wakeup_swapper;
417
418 wakeup_swapper = 0;
419 sleepq_lock(cvp);
420 if (cvp->cv_waiters > 0) {
421 cvp->cv_waiters--;
422 wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, 0);
423 }
424 sleepq_release(cvp);
425 if (wakeup_swapper)
426 kick_proc0();
427 }
428
429 /*
430 * Broadcast a signal to a condition variable. Wakes up all waiting threads.
431 * Should be called with the same mutex as was passed to cv_wait held.
432 */
433 void
434 cv_broadcastpri(struct cv *cvp, int pri)
435 {
436 int wakeup_swapper;
437
438 /*
439 * XXX sleepq_broadcast pri argument changed from -1 meaning
440 * no pri to 0 meaning no pri.
441 */
442 wakeup_swapper = 0;
443 if (pri == -1)
444 pri = 0;
445 sleepq_lock(cvp);
446 if (cvp->cv_waiters > 0) {
447 cvp->cv_waiters = 0;
448 wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0);
449 }
450 sleepq_release(cvp);
451 if (wakeup_swapper)
452 kick_proc0();
453 }
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