native_client_sdk/src/libraries/third_party/pthreads-win32/pthread_cond_signal.c

   1 /*
   2  * pthread_cond_signal.c
   3  *
   4  * Description:
   5  * This translation unit implements condition variables and their primitives.
   6  *
   7  *
   8  * --------------------------------------------------------------------------
   9  *
  10  *      Pthreads-win32 - POSIX Threads Library for Win32
  11  *      Copyright(C) 1998 John E. Bossom
  12  *      Copyright(C) 1999,2005 Pthreads-win32 contributors
  13  *
  14  *      Contact Email: rpj@callisto.canberra.edu.au
  15  *
  16  *      The current list of contributors is contained
  17  *      in the file CONTRIBUTORS included with the source
  18  *      code distribution. The list can also be seen at the
  19  *      following World Wide Web location:
  20  *      http://sources.redhat.com/pthreads-win32/contributors.html
  21  *
  22  *      This library is free software; you can redistribute it and/or
  23  *      modify it under the terms of the GNU Lesser General Public
  24  *      License as published by the Free Software Foundation; either
  25  *      version 2 of the License, or (at your option) any later version.
  26  *
  27  *      This library is distributed in the hope that it will be useful,
  28  *      but WITHOUT ANY WARRANTY; without even the implied warranty of
  29  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  30  *      Lesser General Public License for more details.
  31  *
  32  *      You should have received a copy of the GNU Lesser General Public
  33  *      License along with this library in the file COPYING.LIB;
  34  *      if not, write to the Free Software Foundation, Inc.,
  35  *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  36  *
  37  * -------------------------------------------------------------
  38  * Algorithm:
  39  * See the comments at the top of pthread_cond_wait.c.
  40  */
  41
  42 #include "pthread.h"
  43 #include "implement.h"
  44
  45 static INLINE int
  46 ptw32_cond_unblock (pthread_cond_t * cond, int unblockAll)
  47      /*
  48       * Notes.
  49       *
  50       * Does not use the external mutex for synchronisation,
  51       * therefore semBlockLock is needed.
  52       * mtxUnblockLock is for LEVEL-2 synch. LEVEL-2 is the
  53       * state where the external mutex is not necessarily locked by
  54       * any thread, ie. between cond_wait unlocking and re-acquiring
  55       * the lock after having been signaled or a timeout or
  56       * cancellation.
  57       *
  58       * Uses the following CV elements:
  59       *   nWaitersBlocked
  60       *   nWaitersToUnblock
  61       *   nWaitersGone
  62       *   mtxUnblockLock
  63       *   semBlockLock
  64       *   semBlockQueue
  65       */
  66 {
  67   int result;
  68   pthread_cond_t cv;
  69   int nSignalsToIssue;
  70
  71   if (cond == NULL || *cond == NULL)
  72     {
  73       return EINVAL;
  74     }
  75
  76   cv = *cond;
  77
  78   /*
  79    * No-op if the CV is static and hasn't been initialised yet.
  80    * Assuming that any race condition is harmless.
  81    */
  82   if (cv == PTHREAD_COND_INITIALIZER)
  83     {
  84       return 0;
  85     }
  86
  87   if ((result = pthread_mutex_lock (&(cv->mtxUnblockLock))) != 0)
  88     {
  89       return result;
  90     }
  91
  92   if (0 != cv->nWaitersToUnblock)
  93     {
  94       if (0 == cv->nWaitersBlocked)
  95         {
  96           return pthread_mutex_unlock (&(cv->mtxUnblockLock));
  97         }
  98       if (unblockAll)
  99         {
 100           cv->nWaitersToUnblock += (nSignalsToIssue = cv->nWaitersBlocked);
 101           cv->nWaitersBlocked = 0;
 102         }
 103       else
 104         {
 105           nSignalsToIssue = 1;
 106           cv->nWaitersToUnblock++;
 107           cv->nWaitersBlocked--;
 108         }
 109     }
 110   else if (cv->nWaitersBlocked > cv->nWaitersGone)
 111     {
 112       /* Use the non-cancellable version of sem_wait() */
 113       if (ptw32_semwait (&(cv->semBlockLock)) != 0)
 114         {
 115           result = errno;
 116           (void) pthread_mutex_unlock (&(cv->mtxUnblockLock));
 117           return result;
 118         }
 119       if (0 != cv->nWaitersGone)
 120         {
 121           cv->nWaitersBlocked -= cv->nWaitersGone;
 122           cv->nWaitersGone = 0;
 123         }
 124       if (unblockAll)
 125         {
 126           nSignalsToIssue = cv->nWaitersToUnblock = cv->nWaitersBlocked;
 127           cv->nWaitersBlocked = 0;
 128         }
 129       else
 130         {
 131           nSignalsToIssue = cv->nWaitersToUnblock = 1;
 132           cv->nWaitersBlocked--;
 133         }
 134     }
 135   else
 136     {
 137       return pthread_mutex_unlock (&(cv->mtxUnblockLock));
 138     }
 139
 140   if ((result = pthread_mutex_unlock (&(cv->mtxUnblockLock))) == 0)
 141     {
 142       if (sem_post_multiple (&(cv->semBlockQueue), nSignalsToIssue) != 0)
 143         {
 144           result = errno;
 145         }
 146     }
 147
 148   return result;
 149
 150 }                               /* ptw32_cond_unblock */
 151
 152 int
 153 pthread_cond_signal (pthread_cond_t * cond)
 154      /*
 155       * ------------------------------------------------------
 156       * DOCPUBLIC
 157       *      This function signals a condition variable, waking
 158       *      one waiting thread.
 159       *      If SCHED_FIFO or SCHED_RR policy threads are waiting
 160       *      the highest priority waiter is awakened; otherwise,
 161       *      an unspecified waiter is awakened.
 162       *
 163       * PARAMETERS
 164       *      cond
 165       *              pointer to an instance of pthread_cond_t
 166       *
 167       *
 168       * DESCRIPTION
 169       *      This function signals a condition variable, waking
 170       *      one waiting thread.
 171       *      If SCHED_FIFO or SCHED_RR policy threads are waiting
 172       *      the highest priority waiter is awakened; otherwise,
 173       *      an unspecified waiter is awakened.
 174       *
 175       *      NOTES:
 176       *
 177       *      1)      Use when any waiter can respond and only one need
 178       *              respond (all waiters being equal).
 179       *
 180       * RESULTS
 181       *              0               successfully signaled condition,
 182       *              EINVAL          'cond' is invalid,
 183       *
 184       * ------------------------------------------------------
 185       */
 186 {
 187   /*
 188    * The '0'(FALSE) unblockAll arg means unblock ONE waiter.
 189    */
 190   return (ptw32_cond_unblock (cond, 0));
 191
 192 }                               /* pthread_cond_signal */
 193
 194 int
 195 pthread_cond_broadcast (pthread_cond_t * cond)
 196      /*
 197       * ------------------------------------------------------
 198       * DOCPUBLIC
 199       *      This function broadcasts the condition variable,
 200       *      waking all current waiters.
 201       *
 202       * PARAMETERS
 203       *      cond
 204       *              pointer to an instance of pthread_cond_t
 205       *
 206       *
 207       * DESCRIPTION
 208       *      This function signals a condition variable, waking
 209       *      all waiting threads.
 210       *
 211       *      NOTES:
 212       *
 213       *      1)      Use when more than one waiter may respond to
 214       *              predicate change or if any waiting thread may
 215       *              not be able to respond
 216       *
 217       * RESULTS
 218       *              0               successfully signalled condition to all
 219       *                              waiting threads,
 220       *              EINVAL          'cond' is invalid
 221       *              ENOSPC          a required resource has been exhausted,
 222       *
 223       * ------------------------------------------------------
 224       */
 225 {
 226   /*
 227    * The TRUE unblockAll arg means unblock ALL waiters.
 228    */
 229   return (ptw32_cond_unblock (cond, PTW32_TRUE));
 230
 231 }                               /* pthread_cond_broadcast */