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 "namespace.h"
  30 #include <stdlib.h>
  31 #include <errno.h>
  32 #include <string.h>
  33 #include <pthread.h>
  34 #include <limits.h>
  35 #include "un-namespace.h"
  36
  37 #include "thr_private.h"
  38
  39 /*
  40  * Prototypes
  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 static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
  46 static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
  47                     const struct timespec *abstime, int cancel);
  48 static int cond_signal_common(pthread_cond_t *cond);
  49 static int cond_broadcast_common(pthread_cond_t *cond);
  50
  51 /*
  52  * Double underscore versions are cancellation points.  Single underscore
  53  * versions are not and are provided for libc internal usage (which
  54  * shouldn't introduce cancellation points).
  55  */
  56 __weak_reference(__pthread_cond_wait, pthread_cond_wait);
  57 __weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
  58
  59 __weak_reference(_pthread_cond_init, pthread_cond_init);
  60 __weak_reference(_pthread_cond_destroy, pthread_cond_destroy);
  61 __weak_reference(_pthread_cond_signal, pthread_cond_signal);
  62 __weak_reference(_pthread_cond_broadcast, pthread_cond_broadcast);
  63
  64 #define CV_PSHARED(cvp) (((cvp)->__flags & USYNC_PROCESS_SHARED) != 0)
  65
  66 static int
  67 cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
  68 {
  69         struct pthread_cond     *cvp;
  70         int     error = 0;
  71
  72         if ((cvp = (pthread_cond_t)
  73             calloc(1, sizeof(struct pthread_cond))) == NULL) {
  74                 error = ENOMEM;
  75         } else {
  76                 /*
  77                  * Initialise the condition variable structure:
  78                  */
  79                 if (cond_attr == NULL || *cond_attr == NULL) {
  80                         cvp->__clock_id = CLOCK_REALTIME;
  81                 } else {
  82                         if ((*cond_attr)->c_pshared)
  83                                 cvp->__flags |= USYNC_PROCESS_SHARED;
  84                         cvp->__clock_id = (*cond_attr)->c_clockid;
  85                 }
  86                 *cond = cvp;
  87         }
  88         return (error);
  89 }
  90
  91 static int
  92 init_static(struct pthread *thread, pthread_cond_t *cond)
  93 {
  94         int ret;
  95
  96         THR_LOCK_ACQUIRE(thread, &_cond_static_lock);
  97
  98         if (*cond == NULL)
  99                 ret = cond_init(cond, NULL);
 100         else
 101                 ret = 0;
 102
 103         THR_LOCK_RELEASE(thread, &_cond_static_lock);
 104
 105         return (ret);
 106 }
 107
 108 #define CHECK_AND_INIT_COND                                                     \
 109         if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) {           \
 110                 if (cvp == THR_COND_INITIALIZER) {                              \
 111                         int ret;                                                \
 112                         ret = init_static(_get_curthread(), cond);              \
 113                         if (ret)                                                \
 114                                 return (ret);                                   \
 115                 } else if (cvp == THR_COND_DESTROYED) {                         \
 116                         return (EINVAL);                                        \
 117                 }                                                               \
 118                 cvp = *cond;                                                    \
 119         }
 120
 121 int
 122 _pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
 123 {
 124
 125         *cond = NULL;
 126         return (cond_init(cond, cond_attr));
 127 }
 128
 129 int
 130 _pthread_cond_destroy(pthread_cond_t *cond)
 131 {
 132         struct pthread_cond     *cvp;
 133         int                     error = 0;
 134
 135         if ((cvp = *cond) == THR_COND_INITIALIZER)
 136                 error = 0;
 137         else if (cvp == THR_COND_DESTROYED)
 138                 error = EINVAL;
 139         else {
 140                 cvp = *cond;
 141                 *cond = THR_COND_DESTROYED;
 142
 143                 /*
 144                  * Free the memory allocated for the condition
 145                  * variable structure:
 146                  */
 147                 free(cvp);
 148         }
 149         return (error);
 150 }
 151
 152 /*
 153  * Cancellation behaivor:
 154  *   Thread may be canceled at start, if thread is canceled, it means it
 155  *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
 156  *   not canceled.
 157  *   Thread cancellation never cause wakeup from pthread_cond_signal()
 158  *   to be lost.
 159  */
 160 static int
 161 cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
 162         const struct timespec *abstime, int cancel)
 163 {
 164         struct pthread  *curthread = _get_curthread();
 165         int             recurse;
 166         int             error, error2 = 0;
 167
 168         error = _mutex_cv_detach(mp, &recurse);
 169         if (error != 0)
 170                 return (error);
 171
 172         if (cancel) {
 173                 _thr_cancel_enter2(curthread, 0);
 174                 error = _thr_ucond_wait((struct ucond *)&cvp->__has_kern_waiters,
 175                         (struct umutex *)&mp->m_lock, abstime,
 176                         CVWAIT_ABSTIME|CVWAIT_CLOCKID);
 177                 _thr_cancel_leave(curthread, 0);
 178         } else {
 179                 error = _thr_ucond_wait((struct ucond *)&cvp->__has_kern_waiters,
 180                         (struct umutex *)&mp->m_lock, abstime,
 181                         CVWAIT_ABSTIME|CVWAIT_CLOCKID);
 182         }
 183
 184         /*
 185          * Note that PP mutex and ROBUST mutex may return
 186          * interesting error codes.
 187          */
 188         if (error == 0) {
 189                 error2 = _mutex_cv_lock(mp, recurse);
 190         } else if (error == EINTR || error == ETIMEDOUT) {
 191                 error2 = _mutex_cv_lock(mp, recurse);
 192                 if (error2 == 0 && cancel)
 193                         _thr_testcancel(curthread);
 194                 if (error == EINTR)
 195                         error = 0;
 196         } else {
 197                 /* We know that it didn't unlock the mutex. */
 198                 error2 = _mutex_cv_attach(mp, recurse);
 199                 if (error2 == 0 && cancel)
 200                         _thr_testcancel(curthread);
 201         }
 202         return (error2 != 0 ? error2 : error);
 203 }
 204
 205 /*
 206  * Thread waits in userland queue whenever possible, when thread
 207  * is signaled or broadcasted, it is removed from the queue, and
 208  * is saved in curthread's defer_waiters[] buffer, but won't be
 209  * woken up until mutex is unlocked.
 210  */
 211
 212 static int
 213 cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
 214         const struct timespec *abstime, int cancel)
 215 {
 216         struct pthread  *curthread = _get_curthread();
 217         struct sleepqueue *sq;
 218         int     recurse;
 219         int     error;
 220
 221         if (curthread->wchan != NULL)
 222                 PANIC("thread was already on queue.");
 223
 224         if (cancel)
 225                 _thr_testcancel(curthread);
 226
 227         _sleepq_lock(cvp);
 228         /*
 229          * set __has_user_waiters before unlocking mutex, this allows
 230          * us to check it without locking in pthread_cond_signal().
 231          */
 232         cvp->__has_user_waiters = 1;
 233         curthread->will_sleep = 1;
 234         (void)_mutex_cv_unlock(mp, &recurse);
 235         curthread->mutex_obj = mp;
 236         _sleepq_add(cvp, curthread);
 237         for(;;) {
 238                 _thr_clear_wake(curthread);
 239                 _sleepq_unlock(cvp);
 240
 241                 if (cancel) {
 242                         _thr_cancel_enter2(curthread, 0);
 243                         error = _thr_sleep(curthread, cvp->__clock_id, abstime);
 244                         _thr_cancel_leave(curthread, 0);
 245                 } else {
 246                         error = _thr_sleep(curthread, cvp->__clock_id, abstime);
 247                 }
 248
 249                 _sleepq_lock(cvp);
 250                 if (curthread->wchan == NULL) {
 251                         error = 0;
 252                         break;
 253                 } else if (cancel && SHOULD_CANCEL(curthread)) {
 254                         sq = _sleepq_lookup(cvp);
 255                         cvp->__has_user_waiters =
 256                                 _sleepq_remove(sq, curthread);
 257                         _sleepq_unlock(cvp);
 258                         curthread->mutex_obj = NULL;
 259                         _mutex_cv_lock(mp, recurse);
 260                         if (!THR_IN_CRITICAL(curthread))
 261                                 _pthread_exit(PTHREAD_CANCELED);
 262                         else /* this should not happen */
 263                                 return (0);
 264                 } else if (error == ETIMEDOUT) {
 265                         sq = _sleepq_lookup(cvp);
 266                         cvp->__has_user_waiters =
 267                                 _sleepq_remove(sq, curthread);
 268                         break;
 269                 }
 270         }
 271         _sleepq_unlock(cvp);
 272         curthread->mutex_obj = NULL;
 273         _mutex_cv_lock(mp, recurse);
 274         return (error);
 275 }
 276
 277 static int
 278 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 279         const struct timespec *abstime, int cancel)
 280 {
 281         struct pthread  *curthread = _get_curthread();
 282         struct pthread_cond *cvp;
 283         struct pthread_mutex *mp;
 284         int     error;
 285
 286         CHECK_AND_INIT_COND
 287
 288         mp = *mutex;
 289
 290         if ((error = _mutex_owned(curthread, mp)) != 0)
 291                 return (error);
 292
 293         if (curthread->attr.sched_policy != SCHED_OTHER ||
 294             (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT|UMUTEX_PRIO_INHERIT|
 295                 USYNC_PROCESS_SHARED)) != 0 ||
 296             (cvp->__flags & USYNC_PROCESS_SHARED) != 0)
 297                 return cond_wait_kernel(cvp, mp, abstime, cancel);
 298         else
 299                 return cond_wait_user(cvp, mp, abstime, cancel);
 300 }
 301
 302 int
 303 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 304 {
 305
 306         return (cond_wait_common(cond, mutex, NULL, 0));
 307 }
 308
 309 int
 310 __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 311 {
 312
 313         return (cond_wait_common(cond, mutex, NULL, 1));
 314 }
 315
 316 int
 317 _pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 318                        const struct timespec * abstime)
 319 {
 320
 321         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 322             abstime->tv_nsec >= 1000000000)
 323                 return (EINVAL);
 324
 325         return (cond_wait_common(cond, mutex, abstime, 0));
 326 }
 327
 328 int
 329 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 330                        const struct timespec *abstime)
 331 {
 332
 333         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 334             abstime->tv_nsec >= 1000000000)
 335                 return (EINVAL);
 336
 337         return (cond_wait_common(cond, mutex, abstime, 1));
 338 }
 339
 340 static int
 341 cond_signal_common(pthread_cond_t *cond)
 342 {
 343         struct pthread  *curthread = _get_curthread();
 344         struct pthread *td;
 345         struct pthread_cond *cvp;
 346         struct pthread_mutex *mp;
 347         struct sleepqueue *sq;
 348         int     *waddr;
 349         int     pshared;
 350
 351         /*
 352          * If the condition variable is statically initialized, perform dynamic
 353          * initialization.
 354          */
 355         CHECK_AND_INIT_COND
 356
 357         pshared = CV_PSHARED(cvp);
 358
 359         _thr_ucond_signal((struct ucond *)&cvp->__has_kern_waiters);
 360
 361         if (pshared || cvp->__has_user_waiters == 0)
 362                 return (0);
 363
 364         curthread = _get_curthread();
 365         waddr = NULL;
 366         _sleepq_lock(cvp);
 367         sq = _sleepq_lookup(cvp);
 368         if (sq == NULL) {
 369                 _sleepq_unlock(cvp);
 370                 return (0);
 371         }
 372
 373         td = _sleepq_first(sq);
 374         mp = td->mutex_obj;
 375         cvp->__has_user_waiters = _sleepq_remove(sq, td);
 376         if (mp->m_owner == curthread) {
 377                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 378                         _thr_wake_all(curthread->defer_waiters,
 379                                         curthread->nwaiter_defer);
 380                         curthread->nwaiter_defer = 0;
 381                 }
 382                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 383                         &td->wake_addr->value;
 384                 mp->m_flags |= PMUTEX_FLAG_DEFERED;
 385         } else {
 386                 waddr = &td->wake_addr->value;
 387         }
 388         _sleepq_unlock(cvp);
 389         if (waddr != NULL)
 390                 _thr_set_wake(waddr);
 391         return (0);
 392 }
 393
 394 struct broadcast_arg {
 395         struct pthread *curthread;
 396         unsigned int *waddrs[MAX_DEFER_WAITERS];
 397         int count;
 398 };
 399
 400 static void
 401 drop_cb(struct pthread *td, void *arg)
 402 {
 403         struct broadcast_arg *ba = arg;
 404         struct pthread_mutex *mp;
 405         struct pthread *curthread = ba->curthread;
 406
 407         mp = td->mutex_obj;
 408         if (mp->m_owner == curthread) {
 409                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 410                         _thr_wake_all(curthread->defer_waiters,
 411                                 curthread->nwaiter_defer);
 412                         curthread->nwaiter_defer = 0;
 413                 }
 414                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 415                         &td->wake_addr->value;
 416                 mp->m_flags |= PMUTEX_FLAG_DEFERED;
 417         } else {
 418                 if (ba->count >= MAX_DEFER_WAITERS) {
 419                         _thr_wake_all(ba->waddrs, ba->count);
 420                         ba->count = 0;
 421                 }
 422                 ba->waddrs[ba->count++] = &td->wake_addr->value;
 423         }
 424 }
 425
 426 static int
 427 cond_broadcast_common(pthread_cond_t *cond)
 428 {
 429         int    pshared;
 430         struct pthread_cond *cvp;
 431         struct sleepqueue *sq;
 432         struct broadcast_arg ba;
 433
 434         /*
 435          * If the condition variable is statically initialized, perform dynamic
 436          * initialization.
 437          */
 438         CHECK_AND_INIT_COND
 439
 440         pshared = CV_PSHARED(cvp);
 441
 442         _thr_ucond_broadcast((struct ucond *)&cvp->__has_kern_waiters);
 443
 444         if (pshared || cvp->__has_user_waiters == 0)
 445                 return (0);
 446
 447         ba.curthread = _get_curthread();
 448         ba.count = 0;
 449
 450         _sleepq_lock(cvp);
 451         sq = _sleepq_lookup(cvp);
 452         if (sq == NULL) {
 453                 _sleepq_unlock(cvp);
 454                 return (0);
 455         }
 456         _sleepq_drop(sq, drop_cb, &ba);
 457         cvp->__has_user_waiters = 0;
 458         _sleepq_unlock(cvp);
 459         if (ba.count > 0)
 460                 _thr_wake_all(ba.waddrs, ba.count);
 461         return (0);
 462 }
 463
 464 int
 465 _pthread_cond_signal(pthread_cond_t * cond)
 466 {
 467
 468         return (cond_signal_common(cond));
 469 }
 470
 471 int
 472 _pthread_cond_broadcast(pthread_cond_t * cond)
 473 {
 474
 475         return (cond_broadcast_common(cond));
 476 }