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/5.4/sys/kern/kern_condvar.c 145335 2005-04-20 19:11:07Z cvs2svn $");
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, mp, 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((mp) != NULL, ("%s: mp NULL", __func__)); \
57 mtx_assert((mp), MA_OWNED | MA_NOTRECURSED); \
58 } while (0)
59
60 /*
61 * Initialize a condition variable. Must be called before use.
62 */
63 void
64 cv_init(struct cv *cvp, const char *desc)
65 {
66
67 cvp->cv_description = desc;
68 cvp->cv_waiters = 0;
69 }
70
71 /*
72 * Destroy a condition variable. The condition variable must be re-initialized
73 * in order to be re-used.
74 */
75 void
76 cv_destroy(struct cv *cvp)
77 {
78 #ifdef INVARIANTS
79 struct sleepqueue *sq;
80
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 mtx *mp)
96 {
97 struct sleepqueue *sq;
98 struct thread *td;
99 WITNESS_SAVE_DECL(mp);
100
101 td = curthread;
102 #ifdef KTRACE
103 if (KTRPOINT(td, KTR_CSW))
104 ktrcsw(1, 0);
105 #endif
106 CV_ASSERT(cvp, mp, td);
107 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
108 "Waiting on \"%s\"", cvp->cv_description);
109 WITNESS_SAVE(&mp->mtx_object, mp);
110
111 if (cold || panicstr) {
112 /*
113 * During autoconfiguration, just give interrupts
114 * a chance, then just return. Don't run any other
115 * thread or panic below, in case this is the idle
116 * process and already asleep.
117 */
118 return;
119 }
120
121 sq = sleepq_lookup(cvp);
122
123 cvp->cv_waiters++;
124 DROP_GIANT();
125 mtx_unlock(mp);
126
127 sleepq_add(sq, cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR);
128 sleepq_wait(cvp);
129
130 #ifdef KTRACE
131 if (KTRPOINT(td, KTR_CSW))
132 ktrcsw(0, 0);
133 #endif
134 PICKUP_GIANT();
135 mtx_lock(mp);
136 WITNESS_RESTORE(&mp->mtx_object, mp);
137 }
138
139 /*
140 * Wait on a condition variable, allowing interruption by signals. Return 0 if
141 * the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
142 * a signal was caught. If ERESTART is returned the system call should be
143 * restarted if possible.
144 */
145 int
146 cv_wait_sig(struct cv *cvp, struct mtx *mp)
147 {
148 struct sleepqueue *sq;
149 struct thread *td;
150 struct proc *p;
151 int rval, sig;
152 WITNESS_SAVE_DECL(mp);
153
154 td = curthread;
155 p = td->td_proc;
156 #ifdef KTRACE
157 if (KTRPOINT(td, KTR_CSW))
158 ktrcsw(1, 0);
159 #endif
160 CV_ASSERT(cvp, mp, td);
161 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
162 "Waiting on \"%s\"", cvp->cv_description);
163 WITNESS_SAVE(&mp->mtx_object, mp);
164
165 if (cold || panicstr) {
166 /*
167 * After a panic, or during autoconfiguration, just give
168 * interrupts a chance, then just return; don't run any other
169 * procs or panic below, in case this is the idle process and
170 * already asleep.
171 */
172 return (0);
173 }
174
175 sq = sleepq_lookup(cvp);
176
177 /*
178 * Don't bother sleeping if we are exiting and not the exiting
179 * thread or if our thread is marked as interrupted.
180 */
181 mtx_lock_spin(&sched_lock);
182 rval = thread_sleep_check(td);
183 mtx_unlock_spin(&sched_lock);
184 if (rval != 0) {
185 sleepq_release(cvp);
186 return (rval);
187 }
188
189 cvp->cv_waiters++;
190 DROP_GIANT();
191 mtx_unlock(mp);
192
193 sleepq_add(sq, cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR |
194 SLEEPQ_INTERRUPTIBLE);
195 sig = sleepq_catch_signals(cvp);
196 rval = sleepq_wait_sig(cvp);
197 if (rval == 0)
198 rval = sleepq_calc_signal_retval(sig);
199
200 #ifdef KTRACE
201 if (KTRPOINT(td, KTR_CSW))
202 ktrcsw(0, 0);
203 #endif
204 PICKUP_GIANT();
205 mtx_lock(mp);
206 WITNESS_RESTORE(&mp->mtx_object, mp);
207
208 return (rval);
209 }
210
211 /*
212 * Wait on a condition variable for at most timo/hz seconds. Returns 0 if the
213 * process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout
214 * expires.
215 */
216 int
217 cv_timedwait(struct cv *cvp, struct mtx *mp, int timo)
218 {
219 struct sleepqueue *sq;
220 struct thread *td;
221 int rval;
222 WITNESS_SAVE_DECL(mp);
223
224 td = curthread;
225 rval = 0;
226 #ifdef KTRACE
227 if (KTRPOINT(td, KTR_CSW))
228 ktrcsw(1, 0);
229 #endif
230 CV_ASSERT(cvp, mp, td);
231 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
232 "Waiting on \"%s\"", cvp->cv_description);
233 WITNESS_SAVE(&mp->mtx_object, mp);
234
235 if (cold || panicstr) {
236 /*
237 * After a panic, or during autoconfiguration, just give
238 * interrupts a chance, then just return; don't run any other
239 * thread or panic below, in case this is the idle process and
240 * already asleep.
241 */
242 return 0;
243 }
244
245 sq = sleepq_lookup(cvp);
246
247 cvp->cv_waiters++;
248 DROP_GIANT();
249 mtx_unlock(mp);
250
251 sleepq_add(sq, cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR);
252 sleepq_set_timeout(cvp, timo);
253 rval = sleepq_timedwait(cvp);
254
255 #ifdef KTRACE
256 if (KTRPOINT(td, KTR_CSW))
257 ktrcsw(0, 0);
258 #endif
259 PICKUP_GIANT();
260 mtx_lock(mp);
261 WITNESS_RESTORE(&mp->mtx_object, mp);
262
263 return (rval);
264 }
265
266 /*
267 * Wait on a condition variable for at most timo/hz seconds, allowing
268 * interruption by signals. Returns 0 if the thread was resumed by cv_signal
269 * or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if
270 * a signal was caught.
271 */
272 int
273 cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo)
274 {
275 struct sleepqueue *sq;
276 struct thread *td;
277 struct proc *p;
278 int rval;
279 int sig;
280 WITNESS_SAVE_DECL(mp);
281
282 td = curthread;
283 p = td->td_proc;
284 rval = 0;
285 #ifdef KTRACE
286 if (KTRPOINT(td, KTR_CSW))
287 ktrcsw(1, 0);
288 #endif
289 CV_ASSERT(cvp, mp, td);
290 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
291 "Waiting on \"%s\"", cvp->cv_description);
292 WITNESS_SAVE(&mp->mtx_object, mp);
293
294 if (cold || panicstr) {
295 /*
296 * After a panic, or during autoconfiguration, just give
297 * interrupts a chance, then just return; don't run any other
298 * thread or panic below, in case this is the idle process and
299 * already asleep.
300 */
301 return 0;
302 }
303
304 sq = sleepq_lookup(cvp);
305
306 /*
307 * Don't bother sleeping if we are exiting and not the exiting
308 * thread or if our thread is marked as interrupted.
309 */
310 mtx_lock_spin(&sched_lock);
311 rval = thread_sleep_check(td);
312 mtx_unlock_spin(&sched_lock);
313 if (rval != 0) {
314 sleepq_release(cvp);
315 return (rval);
316 }
317
318 cvp->cv_waiters++;
319 DROP_GIANT();
320 mtx_unlock(mp);
321
322 sleepq_add(sq, cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR |
323 SLEEPQ_INTERRUPTIBLE);
324 sleepq_set_timeout(cvp, timo);
325 sig = sleepq_catch_signals(cvp);
326 rval = sleepq_timedwait_sig(cvp, sig != 0);
327 if (rval == 0)
328 rval = sleepq_calc_signal_retval(sig);
329
330 #ifdef KTRACE
331 if (KTRPOINT(td, KTR_CSW))
332 ktrcsw(0, 0);
333 #endif
334 PICKUP_GIANT();
335 mtx_lock(mp);
336 WITNESS_RESTORE(&mp->mtx_object, mp);
337
338 return (rval);
339 }
340
341 /*
342 * Signal a condition variable, wakes up one waiting thread. Will also wakeup
343 * the swapper if the process is not in memory, so that it can bring the
344 * sleeping process in. Note that this may also result in additional threads
345 * being made runnable. Should be called with the same mutex as was passed to
346 * cv_wait held.
347 */
348 void
349 cv_signal(struct cv *cvp)
350 {
351
352 if (cvp->cv_waiters > 0) {
353 cvp->cv_waiters--;
354 sleepq_signal(cvp, SLEEPQ_CONDVAR, -1);
355 }
356 }
357
358 /*
359 * Broadcast a signal to a condition variable. Wakes up all waiting threads.
360 * Should be called with the same mutex as was passed to cv_wait held.
361 */
362 void
363 cv_broadcastpri(struct cv *cvp, int pri)
364 {
365
366 if (cvp->cv_waiters > 0) {
367 cvp->cv_waiters = 0;
368 sleepq_broadcast(cvp, SLEEPQ_CONDVAR, pri);
369 }
370 }
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