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