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 (at) 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 } 105
