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         int     defered;
 221
 222         if (curthread->wchan != NULL)
 223                 PANIC("thread was already on queue.");
 224
 225         if (cancel)
 226                 _thr_testcancel(curthread);
 227
 228         _sleepq_lock(cvp);
 229         /*
 230          * set __has_user_waiters before unlocking mutex, this allows
 231          * us to check it without locking in pthread_cond_signal().
 232          */
 233         cvp->__has_user_waiters = 1;
 234         defered = 0;
 235         (void)_mutex_cv_unlock(mp, &recurse, &defered);
 236         curthread->mutex_obj = mp;
 237         _sleepq_add(cvp, curthread);
 238         for(;;) {
 239                 _thr_clear_wake(curthread);
 240                 _sleepq_unlock(cvp);
 241                 if (defered) {
 242                         defered = 0;
 243                         if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
 244                                 (void)_umtx_op_err(&mp->m_lock, UMTX_OP_MUTEX_WAKE2,
 245                                          mp->m_lock.m_flags, 0, 0);
 246                 }
 247                 if (curthread->nwaiter_defer > 0) {
 248                         _thr_wake_all(curthread->defer_waiters,
 249                                 curthread->nwaiter_defer);
 250                         curthread->nwaiter_defer = 0;
 251                 }
 252
 253                 if (cancel) {
 254                         _thr_cancel_enter2(curthread, 0);
 255                         error = _thr_sleep(curthread, cvp->__clock_id, abstime);
 256                         _thr_cancel_leave(curthread, 0);
 257                 } else {
 258                         error = _thr_sleep(curthread, cvp->__clock_id, abstime);
 259                 }
 260
 261                 _sleepq_lock(cvp);
 262                 if (curthread->wchan == NULL) {
 263                         error = 0;
 264                         break;
 265                 } else if (cancel && SHOULD_CANCEL(curthread)) {
 266                         sq = _sleepq_lookup(cvp);
 267                         cvp->__has_user_waiters =
 268                                 _sleepq_remove(sq, curthread);
 269                         _sleepq_unlock(cvp);
 270                         curthread->mutex_obj = NULL;
 271                         _mutex_cv_lock(mp, recurse);
 272                         if (!THR_IN_CRITICAL(curthread))
 273                                 _pthread_exit(PTHREAD_CANCELED);
 274                         else /* this should not happen */
 275                                 return (0);
 276                 } else if (error == ETIMEDOUT) {
 277                         sq = _sleepq_lookup(cvp);
 278                         cvp->__has_user_waiters =
 279                                 _sleepq_remove(sq, curthread);
 280                         break;
 281                 }
 282         }
 283         _sleepq_unlock(cvp);
 284         curthread->mutex_obj = NULL;
 285         _mutex_cv_lock(mp, recurse);
 286         return (error);
 287 }
 288
 289 static int
 290 cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
 291         const struct timespec *abstime, int cancel)
 292 {
 293         struct pthread  *curthread = _get_curthread();
 294         struct pthread_cond *cvp;
 295         struct pthread_mutex *mp;
 296         int     error;
 297
 298         CHECK_AND_INIT_COND
 299
 300         mp = *mutex;
 301
 302         if ((error = _mutex_owned(curthread, mp)) != 0)
 303                 return (error);
 304
 305         if (curthread->attr.sched_policy != SCHED_OTHER ||
 306             (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT|UMUTEX_PRIO_INHERIT|
 307                 USYNC_PROCESS_SHARED)) != 0 ||
 308             (cvp->__flags & USYNC_PROCESS_SHARED) != 0)
 309                 return cond_wait_kernel(cvp, mp, abstime, cancel);
 310         else
 311                 return cond_wait_user(cvp, mp, abstime, cancel);
 312 }
 313
 314 int
 315 _pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 316 {
 317
 318         return (cond_wait_common(cond, mutex, NULL, 0));
 319 }
 320
 321 int
 322 __pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
 323 {
 324
 325         return (cond_wait_common(cond, mutex, NULL, 1));
 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, 0));
 338 }
 339
 340 int
 341 __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
 342                        const struct timespec *abstime)
 343 {
 344
 345         if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
 346             abstime->tv_nsec >= 1000000000)
 347                 return (EINVAL);
 348
 349         return (cond_wait_common(cond, mutex, abstime, 1));
 350 }
 351
 352 static int
 353 cond_signal_common(pthread_cond_t *cond)
 354 {
 355         struct pthread  *curthread = _get_curthread();
 356         struct pthread *td;
 357         struct pthread_cond *cvp;
 358         struct pthread_mutex *mp;
 359         struct sleepqueue *sq;
 360         int     *waddr;
 361         int     pshared;
 362
 363         /*
 364          * If the condition variable is statically initialized, perform dynamic
 365          * initialization.
 366          */
 367         CHECK_AND_INIT_COND
 368
 369         pshared = CV_PSHARED(cvp);
 370
 371         _thr_ucond_signal((struct ucond *)&cvp->__has_kern_waiters);
 372
 373         if (pshared || cvp->__has_user_waiters == 0)
 374                 return (0);
 375
 376         curthread = _get_curthread();
 377         waddr = NULL;
 378         _sleepq_lock(cvp);
 379         sq = _sleepq_lookup(cvp);
 380         if (sq == NULL) {
 381                 _sleepq_unlock(cvp);
 382                 return (0);
 383         }
 384
 385         td = _sleepq_first(sq);
 386         mp = td->mutex_obj;
 387         cvp->__has_user_waiters = _sleepq_remove(sq, td);
 388         if (mp->m_owner == curthread) {
 389                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 390                         _thr_wake_all(curthread->defer_waiters,
 391                                         curthread->nwaiter_defer);
 392                         curthread->nwaiter_defer = 0;
 393                 }
 394                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 395                         &td->wake_addr->value;
 396                 mp->m_flags |= PMUTEX_FLAG_DEFERED;
 397         } else {
 398                 waddr = &td->wake_addr->value;
 399         }
 400         _sleepq_unlock(cvp);
 401         if (waddr != NULL)
 402                 _thr_set_wake(waddr);
 403         return (0);
 404 }
 405
 406 struct broadcast_arg {
 407         struct pthread *curthread;
 408         unsigned int *waddrs[MAX_DEFER_WAITERS];
 409         int count;
 410 };
 411
 412 static void
 413 drop_cb(struct pthread *td, void *arg)
 414 {
 415         struct broadcast_arg *ba = arg;
 416         struct pthread_mutex *mp;
 417         struct pthread *curthread = ba->curthread;
 418
 419         mp = td->mutex_obj;
 420         if (mp->m_owner == curthread) {
 421                 if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
 422                         _thr_wake_all(curthread->defer_waiters,
 423                                 curthread->nwaiter_defer);
 424                         curthread->nwaiter_defer = 0;
 425                 }
 426                 curthread->defer_waiters[curthread->nwaiter_defer++] =
 427                         &td->wake_addr->value;
 428                 mp->m_flags |= PMUTEX_FLAG_DEFERED;
 429         } else {
 430                 if (ba->count >= MAX_DEFER_WAITERS) {
 431                         _thr_wake_all(ba->waddrs, ba->count);
 432                         ba->count = 0;
 433                 }
 434                 ba->waddrs[ba->count++] = &td->wake_addr->value;
 435         }
 436 }
 437
 438 static int
 439 cond_broadcast_common(pthread_cond_t *cond)
 440 {
 441         int    pshared;
 442         struct pthread_cond *cvp;
 443         struct sleepqueue *sq;
 444         struct broadcast_arg ba;
 445
 446         /*
 447          * If the condition variable is statically initialized, perform dynamic
 448          * initialization.
 449          */
 450         CHECK_AND_INIT_COND
 451
 452         pshared = CV_PSHARED(cvp);
 453
 454         _thr_ucond_broadcast((struct ucond *)&cvp->__has_kern_waiters);
 455
 456         if (pshared || cvp->__has_user_waiters == 0)
 457                 return (0);
 458
 459         ba.curthread = _get_curthread();
 460         ba.count = 0;
 461
 462         _sleepq_lock(cvp);
 463         sq = _sleepq_lookup(cvp);
 464         if (sq == NULL) {
 465                 _sleepq_unlock(cvp);
 466                 return (0);
 467         }
 468         _sleepq_drop(sq, drop_cb, &ba);
 469         cvp->__has_user_waiters = 0;
 470         _sleepq_unlock(cvp);
 471         if (ba.count > 0)
 472                 _thr_wake_all(ba.waddrs, ba.count);
 473         return (0);
 474 }
 475
 476 int
 477 _pthread_cond_signal(pthread_cond_t * cond)
 478 {
 479
 480         return (cond_signal_common(cond));
 481 }
 482
 483 int
 484 _pthread_cond_broadcast(pthread_cond_t * cond)
 485 {
 486
 487         return (cond_broadcast_common(cond));
 488 }