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

   1 /*
   2  * pthread_barrier_wait.c
   3  *
   4  * Description:
   5  * This translation unit implements barrier primitives.
   6  *
   7  * --------------------------------------------------------------------------
   8  *
   9  *      Pthreads-win32 - POSIX Threads Library for Win32
  10  *      Copyright(C) 1998 John E. Bossom
  11  *      Copyright(C) 1999,2005 Pthreads-win32 contributors
  12  *
  13  *      Contact Email: rpj@callisto.canberra.edu.au
  14  *
  15  *      The current list of contributors is contained
  16  *      in the file CONTRIBUTORS included with the source
  17  *      code distribution. The list can also be seen at the
  18  *      following World Wide Web location:
  19  *      http://sources.redhat.com/pthreads-win32/contributors.html
  20  *
  21  *      This library is free software; you can redistribute it and/or
  22  *      modify it under the terms of the GNU Lesser General Public
  23  *      License as published by the Free Software Foundation; either
  24  *      version 2 of the License, or (at your option) any later version.
  25  *
  26  *      This library is distributed in the hope that it will be useful,
  27  *      but WITHOUT ANY WARRANTY; without even the implied warranty of
  28  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  29  *      Lesser General Public License for more details.
  30  *
  31  *      You should have received a copy of the GNU Lesser General Public
  32  *      License along with this library in the file COPYING.LIB;
  33  *      if not, write to the Free Software Foundation, Inc.,
  34  *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  35  */
  36
  37 #include "pthread.h"
  38 #include "implement.h"
  39
  40
  41 int
  42 pthread_barrier_wait (pthread_barrier_t * barrier)
  43 {
  44   int result;
  45   pthread_barrier_t b;
  46
  47   ptw32_mcs_local_node_t node;
  48
  49   if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
  50     {
  51       return EINVAL;
  52     }
  53
  54   ptw32_mcs_lock_acquire(&(*barrier)->lock, &node);
  55
  56   b = *barrier;
  57   if (--b->nCurrentBarrierHeight == 0)
  58     {
  59       /*
  60        * We are the last thread to arrive at the barrier before it releases us.
  61        * Move our MCS local node to the global scope barrier handle so that the
  62        * last thread out (not necessarily us) can release the lock.
  63        */
  64       ptw32_mcs_node_transfer(&b->proxynode, &node);
  65
  66       /*
  67        * Any threads that have not quite entered sem_wait below when the
  68        * multiple_post has completed will nevertheless continue through
  69        * the semaphore (barrier).
  70        */
  71       result = (b->nInitialBarrierHeight > 1
  72                 ? sem_post_multiple (&(b->semBarrierBreeched),
  73                                      b->nInitialBarrierHeight - 1) : 0);
  74     }
  75   else
  76     {
  77       ptw32_mcs_lock_release(&node);
  78       /*
  79        * Use the non-cancelable version of sem_wait().
  80        *
  81        * It is possible that all nInitialBarrierHeight-1 threads are
  82        * at this point when the last thread enters the barrier, resets
  83        * nCurrentBarrierHeight = nInitialBarrierHeight and leaves.
  84        * If pthread_barrier_destroy is called at that moment then the
  85        * barrier will be destroyed along with the semas.
  86        */
  87       result = ptw32_semwait (&(b->semBarrierBreeched));
  88     }
  89
  90   if ((PTW32_INTERLOCKED_LONG)PTW32_INTERLOCKED_INCREMENT_LONG((PTW32_INTERLOCKED_LONGPTR)&b->nCurrentBarrierHeight)
  91                   == (PTW32_INTERLOCKED_LONG)b->nInitialBarrierHeight)
  92     {
  93       /*
  94        * We are the last thread to cross this barrier
  95        */
  96       ptw32_mcs_lock_release(&b->proxynode);
  97       if (0 == result)
  98         {
  99           result = PTHREAD_BARRIER_SERIAL_THREAD;
 100         }
 101     }
 102
 103   return (result);
 104 }