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
41int
42pthread_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