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/11.2/sys/kern/kern_condvar.c 315386 2017-03-16 07:10:08Z mjg $");
29
30 #include "opt_ktrace.h"
31
32 #include <sys/param.h>
33 #include <sys/systm.h>
34 #include <sys/limits.h>
35 #include <sys/lock.h>
36 #include <sys/mutex.h>
37 #include <sys/proc.h>
38 #include <sys/kernel.h>
39 #include <sys/ktr.h>
40 #include <sys/condvar.h>
41 #include <sys/sched.h>
42 #include <sys/signalvar.h>
43 #include <sys/sleepqueue.h>
44 #include <sys/resourcevar.h>
45 #ifdef KTRACE
46 #include <sys/uio.h>
47 #include <sys/ktrace.h>
48 #endif
49
50 /*
51 * A bound below which cv_waiters is valid. Once cv_waiters reaches this bound,
52 * cv_signal must manually check the wait queue for threads.
53 */
54 #define CV_WAITERS_BOUND INT_MAX
55
56 #define CV_WAITERS_INC(cvp) do { \
57 if ((cvp)->cv_waiters < CV_WAITERS_BOUND) \
58 (cvp)->cv_waiters++; \
59 } while (0)
60
61 /*
62 * Common sanity checks for cv_wait* functions.
63 */
64 #define CV_ASSERT(cvp, lock, td) do { \
65 KASSERT((td) != NULL, ("%s: td NULL", __func__)); \
66 KASSERT(TD_IS_RUNNING(td), ("%s: not TDS_RUNNING", __func__)); \
67 KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__)); \
68 KASSERT((lock) != NULL, ("%s: lock NULL", __func__)); \
69 } while (0)
70
71 /*
72 * Initialize a condition variable. Must be called before use.
73 */
74 void
75 cv_init(struct cv *cvp, const char *desc)
76 {
77
78 cvp->cv_description = desc;
79 cvp->cv_waiters = 0;
80 }
81
82 /*
83 * Destroy a condition variable. The condition variable must be re-initialized
84 * in order to be re-used.
85 */
86 void
87 cv_destroy(struct cv *cvp)
88 {
89 #ifdef INVARIANTS
90 struct sleepqueue *sq;
91
92 sleepq_lock(cvp);
93 sq = sleepq_lookup(cvp);
94 sleepq_release(cvp);
95 KASSERT(sq == NULL, ("%s: associated sleep queue non-empty", __func__));
96 #endif
97 }
98
99 /*
100 * Wait on a condition variable. The current thread is placed on the condition
101 * variable's wait queue and suspended. A cv_signal or cv_broadcast on the same
102 * condition variable will resume the thread. The mutex is released before
103 * sleeping and will be held on return. It is recommended that the mutex be
104 * held when cv_signal or cv_broadcast are called.
105 */
106 void
107 _cv_wait(struct cv *cvp, struct lock_object *lock)
108 {
109 WITNESS_SAVE_DECL(lock_witness);
110 struct lock_class *class;
111 struct thread *td;
112 uintptr_t lock_state;
113
114 td = curthread;
115 lock_state = 0;
116 #ifdef KTRACE
117 if (KTRPOINT(td, KTR_CSW))
118 ktrcsw(1, 0, cv_wmesg(cvp));
119 #endif
120 CV_ASSERT(cvp, lock, td);
121 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
122 "Waiting on \"%s\"", cvp->cv_description);
123 class = LOCK_CLASS(lock);
124
125 if (SCHEDULER_STOPPED_TD(td))
126 return;
127
128 sleepq_lock(cvp);
129
130 CV_WAITERS_INC(cvp);
131 if (lock == &Giant.lock_object)
132 mtx_assert(&Giant, MA_OWNED);
133 DROP_GIANT();
134
135 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
136 if (lock != &Giant.lock_object) {
137 if (class->lc_flags & LC_SLEEPABLE)
138 sleepq_release(cvp);
139 WITNESS_SAVE(lock, lock_witness);
140 lock_state = class->lc_unlock(lock);
141 if (class->lc_flags & LC_SLEEPABLE)
142 sleepq_lock(cvp);
143 }
144 sleepq_wait(cvp, 0);
145
146 #ifdef KTRACE
147 if (KTRPOINT(td, KTR_CSW))
148 ktrcsw(0, 0, cv_wmesg(cvp));
149 #endif
150 PICKUP_GIANT();
151 if (lock != &Giant.lock_object) {
152 class->lc_lock(lock, lock_state);
153 WITNESS_RESTORE(lock, lock_witness);
154 }
155 }
156
157 /*
158 * Wait on a condition variable. This function differs from cv_wait by
159 * not acquiring the mutex after condition variable was signaled.
160 */
161 void
162 _cv_wait_unlock(struct cv *cvp, struct lock_object *lock)
163 {
164 struct lock_class *class;
165 struct thread *td;
166
167 td = curthread;
168 #ifdef KTRACE
169 if (KTRPOINT(td, KTR_CSW))
170 ktrcsw(1, 0, cv_wmesg(cvp));
171 #endif
172 CV_ASSERT(cvp, lock, td);
173 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
174 "Waiting on \"%s\"", cvp->cv_description);
175 KASSERT(lock != &Giant.lock_object,
176 ("cv_wait_unlock cannot be used with Giant"));
177 class = LOCK_CLASS(lock);
178
179 if (SCHEDULER_STOPPED_TD(td)) {
180 class->lc_unlock(lock);
181 return;
182 }
183
184 sleepq_lock(cvp);
185
186 CV_WAITERS_INC(cvp);
187 DROP_GIANT();
188
189 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
190 if (class->lc_flags & LC_SLEEPABLE)
191 sleepq_release(cvp);
192 class->lc_unlock(lock);
193 if (class->lc_flags & LC_SLEEPABLE)
194 sleepq_lock(cvp);
195 sleepq_wait(cvp, 0);
196
197 #ifdef KTRACE
198 if (KTRPOINT(td, KTR_CSW))
199 ktrcsw(0, 0, cv_wmesg(cvp));
200 #endif
201 PICKUP_GIANT();
202 }
203
204 /*
205 * Wait on a condition variable, allowing interruption by signals. Return 0 if
206 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
207 * a signal was caught. If ERESTART is returned the system call should be
208 * restarted if possible.
209 */
210 int
211 _cv_wait_sig(struct cv *cvp, struct lock_object *lock)
212 {
213 WITNESS_SAVE_DECL(lock_witness);
214 struct lock_class *class;
215 struct thread *td;
216 uintptr_t lock_state;
217 int 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 (SCHEDULER_STOPPED_TD(td))
231 return (0);
232
233 sleepq_lock(cvp);
234
235 CV_WAITERS_INC(cvp);
236 if (lock == &Giant.lock_object)
237 mtx_assert(&Giant, MA_OWNED);
238 DROP_GIANT();
239
240 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
241 SLEEPQ_INTERRUPTIBLE, 0);
242 if (lock != &Giant.lock_object) {
243 if (class->lc_flags & LC_SLEEPABLE)
244 sleepq_release(cvp);
245 WITNESS_SAVE(lock, lock_witness);
246 lock_state = class->lc_unlock(lock);
247 if (class->lc_flags & LC_SLEEPABLE)
248 sleepq_lock(cvp);
249 }
250 rval = sleepq_wait_sig(cvp, 0);
251
252 #ifdef KTRACE
253 if (KTRPOINT(td, KTR_CSW))
254 ktrcsw(0, 0, cv_wmesg(cvp));
255 #endif
256 PICKUP_GIANT();
257 if (lock != &Giant.lock_object) {
258 class->lc_lock(lock, lock_state);
259 WITNESS_RESTORE(lock, lock_witness);
260 }
261
262 return (rval);
263 }
264
265 /*
266 * Wait on a condition variable for (at most) the value specified in sbt
267 * argument. Returns 0 if the process was resumed by cv_signal or cv_broadcast,
268 * EWOULDBLOCK if the timeout expires.
269 */
270 int
271 _cv_timedwait_sbt(struct cv *cvp, struct lock_object *lock, sbintime_t sbt,
272 sbintime_t pr, int flags)
273 {
274 WITNESS_SAVE_DECL(lock_witness);
275 struct lock_class *class;
276 struct thread *td;
277 int lock_state, rval;
278
279 td = curthread;
280 lock_state = 0;
281 #ifdef KTRACE
282 if (KTRPOINT(td, KTR_CSW))
283 ktrcsw(1, 0, cv_wmesg(cvp));
284 #endif
285 CV_ASSERT(cvp, lock, td);
286 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
287 "Waiting on \"%s\"", cvp->cv_description);
288 class = LOCK_CLASS(lock);
289
290 if (SCHEDULER_STOPPED_TD(td))
291 return (0);
292
293 sleepq_lock(cvp);
294
295 CV_WAITERS_INC(cvp);
296 if (lock == &Giant.lock_object)
297 mtx_assert(&Giant, MA_OWNED);
298 DROP_GIANT();
299
300 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR, 0);
301 sleepq_set_timeout_sbt(cvp, sbt, pr, flags);
302 if (lock != &Giant.lock_object) {
303 if (class->lc_flags & LC_SLEEPABLE)
304 sleepq_release(cvp);
305 WITNESS_SAVE(lock, lock_witness);
306 lock_state = class->lc_unlock(lock);
307 if (class->lc_flags & LC_SLEEPABLE)
308 sleepq_lock(cvp);
309 }
310 rval = sleepq_timedwait(cvp, 0);
311
312 #ifdef KTRACE
313 if (KTRPOINT(td, KTR_CSW))
314 ktrcsw(0, 0, cv_wmesg(cvp));
315 #endif
316 PICKUP_GIANT();
317 if (lock != &Giant.lock_object) {
318 class->lc_lock(lock, lock_state);
319 WITNESS_RESTORE(lock, lock_witness);
320 }
321
322 return (rval);
323 }
324
325 /*
326 * Wait on a condition variable for (at most) the value specified in sbt
327 * argument, allowing interruption by signals.
328 * Returns 0 if the thread was resumed by cv_signal or cv_broadcast,
329 * EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if a signal
330 * was caught.
331 */
332 int
333 _cv_timedwait_sig_sbt(struct cv *cvp, struct lock_object *lock,
334 sbintime_t sbt, sbintime_t pr, int flags)
335 {
336 WITNESS_SAVE_DECL(lock_witness);
337 struct lock_class *class;
338 struct thread *td;
339 int lock_state, rval;
340
341 td = curthread;
342 lock_state = 0;
343 #ifdef KTRACE
344 if (KTRPOINT(td, KTR_CSW))
345 ktrcsw(1, 0, cv_wmesg(cvp));
346 #endif
347 CV_ASSERT(cvp, lock, td);
348 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, lock,
349 "Waiting on \"%s\"", cvp->cv_description);
350 class = LOCK_CLASS(lock);
351
352 if (SCHEDULER_STOPPED_TD(td))
353 return (0);
354
355 sleepq_lock(cvp);
356
357 CV_WAITERS_INC(cvp);
358 if (lock == &Giant.lock_object)
359 mtx_assert(&Giant, MA_OWNED);
360 DROP_GIANT();
361
362 sleepq_add(cvp, lock, cvp->cv_description, SLEEPQ_CONDVAR |
363 SLEEPQ_INTERRUPTIBLE, 0);
364 sleepq_set_timeout_sbt(cvp, sbt, pr, flags);
365 if (lock != &Giant.lock_object) {
366 if (class->lc_flags & LC_SLEEPABLE)
367 sleepq_release(cvp);
368 WITNESS_SAVE(lock, lock_witness);
369 lock_state = class->lc_unlock(lock);
370 if (class->lc_flags & LC_SLEEPABLE)
371 sleepq_lock(cvp);
372 }
373 rval = sleepq_timedwait_sig(cvp, 0);
374
375 #ifdef KTRACE
376 if (KTRPOINT(td, KTR_CSW))
377 ktrcsw(0, 0, cv_wmesg(cvp));
378 #endif
379 PICKUP_GIANT();
380 if (lock != &Giant.lock_object) {
381 class->lc_lock(lock, lock_state);
382 WITNESS_RESTORE(lock, lock_witness);
383 }
384
385 return (rval);
386 }
387
388 /*
389 * Signal a condition variable, wakes up one waiting thread. Will also wakeup
390 * the swapper if the process is not in memory, so that it can bring the
391 * sleeping process in. Note that this may also result in additional threads
392 * being made runnable. Should be called with the same mutex as was passed to
393 * cv_wait held.
394 */
395 void
396 cv_signal(struct cv *cvp)
397 {
398 int wakeup_swapper;
399
400 if (cvp->cv_waiters == 0)
401 return;
402 wakeup_swapper = 0;
403 sleepq_lock(cvp);
404 if (cvp->cv_waiters > 0) {
405 if (cvp->cv_waiters == CV_WAITERS_BOUND &&
406 sleepq_lookup(cvp) == NULL) {
407 cvp->cv_waiters = 0;
408 } else {
409 if (cvp->cv_waiters < CV_WAITERS_BOUND)
410 cvp->cv_waiters--;
411 wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0,
412 0);
413 }
414 }
415 sleepq_release(cvp);
416 if (wakeup_swapper)
417 kick_proc0();
418 }
419
420 /*
421 * Broadcast a signal to a condition variable. Wakes up all waiting threads.
422 * Should be called with the same mutex as was passed to cv_wait held.
423 */
424 void
425 cv_broadcastpri(struct cv *cvp, int pri)
426 {
427 int wakeup_swapper;
428
429 if (cvp->cv_waiters == 0)
430 return;
431 /*
432 * XXX sleepq_broadcast pri argument changed from -1 meaning
433 * no pri to 0 meaning no pri.
434 */
435 wakeup_swapper = 0;
436 if (pri == -1)
437 pri = 0;
438 sleepq_lock(cvp);
439 if (cvp->cv_waiters > 0) {
440 cvp->cv_waiters = 0;
441 wakeup_swapper = sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri, 0);
442 }
443 sleepq_release(cvp);
444 if (wakeup_swapper)
445 kick_proc0();
446 }
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