1 /*
2  * Copyright (c) 2005 David Xu <davidxu@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 unmodified, this list of conditions, and the following
10  *    disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  *
15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25  *
26  * $DragonFly: src/lib/libthread_xu/thread/thr_cond.c,v 1.10 2006/04/06 23:50:13 davidxu Exp $
27  */
28 
29 #include "namespace.h"
30 #include <machine/tls.h>
31 
32 #include <stdlib.h>
33 #include <string.h>
34 #include <pthread.h>
35 #include <limits.h>
36 #include "un-namespace.h"
37 
38 #include "thr_private.h"
39 
40 umtx_t		_cond_static_lock;
41 
42 int	__pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex);
43 int	__pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
44 		       const struct timespec *abstime);
45 /*
46  * Prototypes
47  */
48 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
49 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
50 		    const struct timespec *abstime, int cancel);
51 static int cond_signal_common(pthread_cond_t *cond, int broadcast);
52 
53 static int
54 cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
55 {
56 	pthread_cond_t	pcond;
57 	int             rval = 0;
58 
59 	if ((pcond = (pthread_cond_t)
60 	    malloc(sizeof(struct pthread_cond))) == NULL) {
61 		rval = ENOMEM;
62 	} else {
63 		/*
64 		 * Initialise the condition variable structure:
65 		 */
66 		_thr_umtx_init(&pcond->c_lock);
67 		pcond->c_seqno = 0;
68 		pcond->c_waiters = 0;
69 		pcond->c_wakeups = 0;
70 		if (cond_attr == NULL || *cond_attr == NULL) {
71 			pcond->c_pshared = 0;
72 			pcond->c_clockid = CLOCK_REALTIME;
73 		} else {
74 			pcond->c_pshared = (*cond_attr)->c_pshared;
75 			pcond->c_clockid = (*cond_attr)->c_clockid;
76 		}
77 		*cond = pcond;
78 	}
79 	/* Return the completion status: */
80 	return (rval);
81 }
82 
83 static int
84 init_static(struct pthread *thread, pthread_cond_t *cond)
85 {
86 	int ret;
87 
88 	THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
89 
90 	if (*cond == NULL)
91 		ret = cond_init(cond, NULL);
92 	else
93 		ret = 0;
94 
95 	THR_LOCK_RELEASE(thread, &_cond_static_lock);
96 
97 	return (ret);
98 }
99 
100 int
101 _pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
102 {
103 	*cond = NULL;
104 	return cond_init(cond, cond_attr);
105 }
106 
107 int
108 _pthread_cond_destroy(pthread_cond_t *cond)
109 {
110 	struct pthread_cond	*cv;
111 	struct pthread		*curthread = tls_get_curthread();
112 	int			rval = 0;
113 
114 	if (*cond == NULL)
115 		rval = EINVAL;
116 	else {
117 		/* Lock the condition variable structure: */
118 		THR_LOCK_ACQUIRE(curthread, &(*cond)->c_lock);
119 		if ((*cond)->c_waiters + (*cond)->c_wakeups != 0) {
120 			THR_LOCK_RELEASE(curthread, &(*cond)->c_lock);
121 			return (EBUSY);
122 		}
123 
124 		/*
125 		 * NULL the caller's pointer now that the condition
126 		 * variable has been destroyed:
127 		 */
128 		cv = *cond;
129 		*cond = NULL;
130 
131 		/* Unlock the condition variable structure: */
132 		THR_LOCK_RELEASE(curthread, &cv->c_lock);
133 
134 		/* Free the cond lock structure: */
135 
136 		/*
137 		 * Free the memory allocated for the condition
138 		 * variable structure:
139 		 */
140 		free(cv);
141 
142 	}
143 	/* Return the completion status: */
144 	return (rval);
145 }
146 
147 struct cond_cancel_info
148 {
149 	pthread_mutex_t	*mutex;
150 	pthread_cond_t	*cond;
151 	int		seqno;
152 	int		count;
153 };
154 
155 static void
156 cond_cancel_handler(void *arg)
157 {
158 	struct pthread *curthread = tls_get_curthread();
159 	struct cond_cancel_info *info = (struct cond_cancel_info *)arg;
160 	pthread_cond_t cv;
161 
162 	cv = *(info->cond);
163 	THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
164 	if (cv->c_seqno != info->seqno && cv->c_wakeups != 0) {
165 		if (cv->c_waiters > 0) {
166 			cv->c_seqno++;
167 			_thr_umtx_wake(&cv->c_seqno, 1);
168 		} else
169 			cv->c_wakeups--;
170 	} else {
171 		cv->c_waiters--;
172 	}
173 	THR_LOCK_RELEASE(curthread, &cv->c_lock);
174 
175 	_mutex_cv_lock(info->mutex, info->count);
176 }
177 
178 static int
179 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
180 	const struct timespec *abstime, int cancel)
181 {
182 	struct pthread	*curthread = tls_get_curthread();
183 	struct timespec ts, ts2, *tsp;
184 	struct cond_cancel_info info;
185 	pthread_cond_t  cv;
186 	int		seq, oldseq;
187 	int		oldcancel;
188 	int		ret = 0;
189 
190 	/*
191 	 * If the condition variable is statically initialized,
192 	 * perform the dynamic initialization:
193 	 */
194 	if (__predict_false(*cond == NULL &&
195 	    (ret = init_static(curthread, cond)) != 0))
196 		return (ret);
197 
198 	cv = *cond;
199 	THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
200 	ret = _mutex_cv_unlock(mutex, &info.count);
201 	if (ret) {
202 		THR_LOCK_RELEASE(curthread, &cv->c_lock);
203 		return (ret);
204 	}
205 	oldseq = seq = cv->c_seqno;
206 	info.mutex = mutex;
207 	info.cond  = cond;
208 	info.seqno = oldseq;
209 
210 	cv->c_waiters++;
211 	do {
212 		THR_LOCK_RELEASE(curthread, &cv->c_lock);
213 
214 		if (abstime != NULL) {
215 			clock_gettime(cv->c_clockid, &ts);
216 			TIMESPEC_SUB(&ts2, abstime, &ts);
217 			tsp = &ts2;
218 		} else
219 			tsp = NULL;
220 
221 		if (cancel) {
222 			THR_CLEANUP_PUSH(curthread, cond_cancel_handler, &info);
223 			oldcancel = _thr_cancel_enter(curthread);
224 			ret = _thr_umtx_wait(&cv->c_seqno, seq, tsp,
225 				cv->c_clockid);
226 			_thr_cancel_leave(curthread, oldcancel);
227 			THR_CLEANUP_POP(curthread, 0);
228 		} else {
229 			ret = _thr_umtx_wait(&cv->c_seqno, seq, tsp,
230 				cv->c_clockid);
231 		}
232 
233 		THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
234 		seq = cv->c_seqno;
235 		if (abstime != NULL && ret == ETIMEDOUT)
236 			break;
237 
238 		/*
239 		 * loop if we have never been told to wake up
240 		 * or we lost a race.
241 		 */
242 	} while (seq == oldseq || cv->c_wakeups == 0);
243 
244 	if (seq != oldseq && cv->c_wakeups != 0) {
245 		cv->c_wakeups--;
246 		ret = 0;
247 	} else {
248 		cv->c_waiters--;
249 	}
250 	THR_LOCK_RELEASE(curthread, &cv->c_lock);
251 	_mutex_cv_lock(mutex, info.count);
252 	return (ret);
253 }
254 
255 int
256 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
257 {
258 
259 	return (cond_wait_common(cond, mutex, NULL, 0));
260 }
261 
262 int
263 __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
264 {
265 
266 	return (cond_wait_common(cond, mutex, NULL, 1));
267 }
268 
269 int
270 _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex,
271 		       const struct timespec * abstime)
272 {
273 	if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
274 	    abstime->tv_nsec >= 1000000000)
275 		return (EINVAL);
276 
277 	return (cond_wait_common(cond, mutex, abstime, 0));
278 }
279 
280 int
281 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
282 		       const struct timespec *abstime)
283 {
284 	if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
285 	    abstime->tv_nsec >= 1000000000)
286 		return (EINVAL);
287 
288 	return (cond_wait_common(cond, mutex, abstime, 1));
289 }
290 
291 static int
292 cond_signal_common(pthread_cond_t *cond, int broadcast)
293 {
294 	struct pthread	*curthread = tls_get_curthread();
295 	pthread_cond_t	cv;
296 	int		ret = 0;
297 
298 	/*
299 	 * If the condition variable is statically initialized, perform dynamic
300 	 * initialization.
301 	 */
302 	if (__predict_false(*cond == NULL &&
303 	    (ret = init_static(curthread, cond)) != 0))
304 		return (ret);
305 
306 	cv = *cond;
307 	/* Lock the condition variable structure. */
308 	THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
309 	if (cv->c_waiters) {
310 		if (!broadcast) {
311 			cv->c_wakeups++;
312 			cv->c_waiters--;
313 			cv->c_seqno++;
314 			_thr_umtx_wake(&cv->c_seqno, 1);
315 		} else {
316 			cv->c_wakeups += cv->c_waiters;
317 			cv->c_waiters = 0;
318 			cv->c_seqno++;
319 			_thr_umtx_wake(&cv->c_seqno, INT_MAX);
320 		}
321 	}
322 	THR_LOCK_RELEASE(curthread, &cv->c_lock);
323 	return (ret);
324 }
325 
326 int
327 _pthread_cond_signal(pthread_cond_t * cond)
328 {
329 
330 	return (cond_signal_common(cond, 0));
331 }
332 
333 int
334 _pthread_cond_broadcast(pthread_cond_t * cond)
335 {
336 
337 	return (cond_signal_common(cond, 1));
338 }
339 
340 /*
341  * Double underscore versions are cancellation points.  Single underscore
342  * versions are not and are provided for libc internal usage (which
343  * shouldn't introduce cancellation points).
344  */
345 __strong_reference(__pthread_cond_wait, pthread_cond_wait);
346 __strong_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
347 
348 __strong_reference(_pthread_cond_init, pthread_cond_init);
349 __strong_reference(_pthread_cond_destroy, pthread_cond_destroy);
350 __strong_reference(_pthread_cond_signal, pthread_cond_signal);
351 __strong_reference(_pthread_cond_broadcast, pthread_cond_broadcast);
352 
353