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 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
35 */
36
37 #include "pthread.h"
38 #include "implement.h"
39
40
41 int
pthread_barrier_wait(pthread_barrier_t * barrier)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