lib/libthr/thread/thr_cond.c

   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  * $FreeBSD$
  27  */
  28
  29 #include <stdlib.h>
  30 #include <errno.h>
  31 #include <string.h>
  32 #include <pthread.h>
  33 #include <limits.h>
  34
  35 #include "thr_private.h"
  36
  37 /*
  38  * Prototypes
  39  */
  40 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
  41 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
  42                     const struct timespec *abstime, int cancel);
  43 static int cond_signal_common(pthread_cond_t *cond, int broadcast);
  44
  45 /*
  46  * Double underscore versions are cancellation points.  Single underscore
  47  * versions are not and are provided for libc internal usage (which
  48  * shouldn't introduce cancellation points).
  49  */
  50 __weak_reference(__pthread_cond_wait, pthread_cond_wait);
  51 __weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
  52
  53 __weak_reference(_pthread_cond_init, pthread_cond_init);
  54 __weak_reference(_pthread_cond_destroy, pthread_cond_destroy);
  55 __weak_reference(_pthread_cond_signal, pthread_cond_signal);
  56 __weak_reference(_pthread_cond_broadcast, pthread_cond_broadcast);
  57
  58 static int
  59 cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
  60 {
  61         pthread_cond_t  pcond;
  62         int             rval = 0;
  63
  64         if ((pcond = (pthread_cond_t)
  65             malloc(sizeof(struct pthread_cond))) == NULL) {
  66                 rval = ENOMEM;
  67         } else {
  68                 /*
  69                  * Initialise the condition variable structure:
  70                  */
  71                 _thr_umtx_init(&pcond->c_lock);
  72                 pcond->c_seqno = 0;
  73                 pcond->c_waiters = 0;
  74                 pcond->c_wakeups = 0;
  75                 if (cond_attr == NULL || *cond_attr == NULL) {
  76                         pcond->c_pshared = 0;
  77                         pcond->c_clockid = CLOCK_REALTIME;
  78                 } else {
  79                         pcond->c_pshared = (*cond_attr)->c_pshared;
  80                         pcond->c_clockid = (*cond_attr)->c_clockid;
  81                 }
  82                 *cond = pcond;
  83         }
  84         /* Return the completion status: */
  85         return (rval);
  86 }
  87
  88 static int
  89 init_static(struct pthread *thread, pthread_cond_t *cond)
  90 {
  91         int ret;
  92
  93         THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
  94
  95         if (*cond == NULL)
  96                 ret = cond_init(cond, NULL);
  97         else
  98                 ret = 0;
  99
 100         THR_LOCK_RELEASE(thread, &_cond_static_lock);
 101
 102         return (ret);
 103 }
 104
 105 int
 106 _pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
 107 {
 108
 109         *cond = NULL;
 110         return (cond_init(cond, cond_attr));
 111 }
 112
 113 int
 114 _pthread_cond_destroy(pthread_cond_t *cond)
 115 {
 116         struct pthread_cond     *cv;
 117         struct pthread          *curthread = _get_curthread();
 118         int                     rval = 0;
 119
 120         if (*cond == NULL)
 121                 rval = EINVAL;
 122         else {
 123                 /* Lock the condition variable structure: */
 124                 THR_LOCK_ACQUIRE(curthread, &(*cond)->c_lock);
 125                 if ((*cond)->c_waiters + (*cond)->c_wakeups != 0) {
 126                         THR_LOCK_RELEASE(curthread, &(*cond)->c_lock);
 127                         return (EBUSY);
 128                 }
 129
 130                 /*
 131                  * NULL the caller's pointer now that the condition
 132                  * variable has been destroyed:
 133                  */
 134                 cv = *cond;
 135                 *cond = NULL;
 136
 137                 /* Unlock the condition variable structure: */
 138                 THR_LOCK_RELEASE(curthread, &cv->c_lock);
 139
 140                 /* Free the cond lock structure: */
 141
 142                 /*
 143                  * Free the memory allocated for the condition
 144                  * variable structure:
 145                  */
 146                 free(cv);
 147
 148         }
 149         /* Return the completion status: */
 150         return (rval);
 151 }
 152
 153 struct cond_cancel_info
 154 {
 155         pthread_mutex_t *mutex;
 156         pthread_cond_t  *cond;
 157         long            seqno;
 158 };
 159
 160 static void
 161 cond_cancel_handler(void *arg)
 162 {
 163         struct pthread *curthread = _get_curthread();
 164         struct cond_cancel_info *cci = (struct cond_cancel_info *)arg;
 165         pthread_cond_t cv;
 166
 167         cv = *(cci->cond);
 168         THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
 169         if (cv->c_seqno != cci->seqno && cv->c_wakeups != 0) {
 170                 if (cv->c_waiters > 0) {
 171                         cv->c_seqno++;
 172                         _thr_umtx_wake(&cv->c_seqno, 1);
 173                 } else
 174                         cv->c_wakeups--;
 175         } else {
 176                 cv->c_waiters--;
 177         }
 178         THR_LOCK_RELEASE(curthread, &cv->c_lock);
 179
 180         _mutex_cv_lock(cci->mutex);
 181 }
 182
 183 static int
 184 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 185         const struct timespec *abstime, int cancel)
 186 {
 187         struct pthread  *curthread = _get_curthread();
 188         struct timespec ts, ts2, *tsp;
 189         struct cond_cancel_info cci;
 190         pthread_cond_t  cv;
 191         long            seq, oldseq;
 192         int             oldcancel;
 193         int             ret = 0;
 194
 195         /*
 196          * If the condition variable is statically initialized,
 197          * perform the dynamic initialization:
 198          */
 199         if (__predict_false(*cond == NULL &&
 200             (ret = init_static(curthread, cond)) != 0))
 201                 return (ret);
 202
 203         cv = *cond;
 204         THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
 205         ret = _mutex_cv_unlock(mutex);
 206         if (ret) {
 207                 THR_LOCK_RELEASE(curthread, &cv->c_lock);
 208                 return (ret);
 209         }
 210         oldseq = seq = cv->c_seqno;
 211         cci.mutex = mutex;
 212         cci.cond  = cond;
 213         cci.seqno = oldseq;
 214
 215         cv->c_waiters++;
 216         do {
 217                 THR_LOCK_RELEASE(curthread, &cv->c_lock);
 218
 219                 if (abstime != NULL) {
 220                         clock_gettime(cv->c_clockid, &ts);
 221                         TIMESPEC_SUB(&ts2, abstime, &ts);
 222                         tsp = &ts2;
 223                 } else
 224                         tsp = NULL;
 225
 226                 if (cancel) {
 227                         THR_CLEANUP_PUSH(curthread, cond_cancel_handler, &cci);
 228                         oldcancel = _thr_cancel_enter(curthread);
 229                         ret = _thr_umtx_wait(&cv->c_seqno, seq, tsp);
 230                         _thr_cancel_leave(curthread, oldcancel);
 231                         THR_CLEANUP_POP(curthread, 0);
 232                 } else {
 233                         ret = _thr_umtx_wait(&cv->c_seqno, seq, tsp);
 234                 }
 235
 236                 THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
 237                 seq = cv->c_seqno;
 238                 if (abstime != NULL && ret == ETIMEDOUT)
 239                         break;
 240
 241                 /*
 242                  * loop if we have never been told to wake up
 243                  * or we lost a race.
 244                  */
 245         } while (seq == oldseq || cv->c_wakeups == 0);
 246
 247         if (seq != oldseq && cv->c_wakeups != 0) {
 248                 cv->c_wakeups--;
 249                 ret = 0;
 250         } else {
 251                 cv->c_waiters--;
 252         }
 253         THR_LOCK_RELEASE(curthread, &cv->c_lock);
 254         _mutex_cv_lock(mutex);
 255         return (ret);
 256 }
 257
 258 int
 259 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 260 {
 261
 262         return (cond_wait_common(cond, mutex, NULL, 0));
 263 }
 264
 265 int
 266 __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 267 {
 268
 269         return (cond_wait_common(cond, mutex, NULL, 1));
 270 }
 271
 272 int
 273 _pthread_cond_timedwait(pthread_cond_t * cond, pthread_mutex_t * mutex,
 274                        const struct timespec * abstime)
 275 {
 276
 277         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 278             abstime->tv_nsec >= 1000000000)
 279                 return (EINVAL);
 280
 281         return (cond_wait_common(cond, mutex, abstime, 0));
 282 }
 283
 284 int
 285 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 286                        const struct timespec *abstime)
 287 {
 288
 289         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 290             abstime->tv_nsec >= 1000000000)
 291                 return (EINVAL);
 292
 293         return (cond_wait_common(cond, mutex, abstime, 1));
 294 }
 295
 296 static int
 297 cond_signal_common(pthread_cond_t *cond, int broadcast)
 298 {
 299         struct pthread  *curthread = _get_curthread();
 300         pthread_cond_t  cv;
 301         int             ret = 0, oldwaiters;
 302
 303         /*
 304          * If the condition variable is statically initialized, perform dynamic
 305          * initialization.
 306          */
 307         if (__predict_false(*cond == NULL &&
 308             (ret = init_static(curthread, cond)) != 0))
 309                 return (ret);
 310
 311         cv = *cond;
 312         /* Lock the condition variable structure. */
 313         THR_LOCK_ACQUIRE(curthread, &cv->c_lock);
 314         if (cv->c_waiters) {
 315                 if (!broadcast) {
 316                         cv->c_wakeups++;
 317                         cv->c_waiters--;
 318                         cv->c_seqno++;
 319                         _thr_umtx_wake(&cv->c_seqno, 1);
 320                 } else {
 321                         oldwaiters = cv->c_waiters;
 322                         cv->c_wakeups += cv->c_waiters;
 323                         cv->c_waiters = 0;
 324                         cv->c_seqno++;
 325                         _thr_umtx_wake(&cv->c_seqno, oldwaiters);
 326                 }
 327         }
 328         THR_LOCK_RELEASE(curthread, &cv->c_lock);
 329         return (ret);
 330 }
 331
 332 int
 333 _pthread_cond_signal(pthread_cond_t * cond)
 334 {
 335
 336         return (cond_signal_common(cond, 0));
 337 }
 338
 339 int
 340 _pthread_cond_broadcast(pthread_cond_t * cond)
 341 {
 342
 343         return (cond_signal_common(cond, 1));
 344 }