1 /* Copyright (C) 2003, 2004, 2007 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19 #include <errno.h>
20 #include <sysdep.h>
21 #include <lowlevellock.h>
22 #include <pthreadP.h>
23
24
25 /* Wait on barrier. */
26 int
pthread_barrier_wait(pthread_barrier_t * barrier)27 pthread_barrier_wait (
28 pthread_barrier_t *barrier)
29 {
30 struct pthread_barrier *ibarrier = (struct pthread_barrier *) barrier;
31 int result = 0;
32
33 /* Make sure we are alone. */
34 lll_lock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
35
36 /* One more arrival. */
37 --ibarrier->left;
38
39 /* Are these all? */
40 if (ibarrier->left == 0)
41 {
42 /* Yes. Increment the event counter to avoid invalid wake-ups and
43 tell the current waiters that it is their turn. */
44 ++ibarrier->curr_event;
45
46 /* Wake up everybody. */
47 lll_futex_wake (&ibarrier->curr_event, INT_MAX,
48 ibarrier->private ^ FUTEX_PRIVATE_FLAG);
49
50 /* This is the thread which finished the serialization. */
51 result = PTHREAD_BARRIER_SERIAL_THREAD;
52 }
53 else
54 {
55 /* The number of the event we are waiting for. The barrier's event
56 number must be bumped before we continue. */
57 unsigned int event = ibarrier->curr_event;
58
59 /* Before suspending, make the barrier available to others. */
60 lll_unlock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
61
62 /* Wait for the event counter of the barrier to change. */
63 do
64 lll_futex_wait (&ibarrier->curr_event, event,
65 ibarrier->private ^ FUTEX_PRIVATE_FLAG);
66 while (event == ibarrier->curr_event);
67 }
68
69 /* Make sure the init_count is stored locally or in a register. */
70 unsigned int init_count = ibarrier->init_count;
71
72 /* If this was the last woken thread, unlock. */
73 if (atomic_increment_val (&ibarrier->left) == init_count)
74 /* We are done. */
75 lll_unlock (ibarrier->lock, ibarrier->private ^ FUTEX_PRIVATE_FLAG);
76
77 return result;
78 }
79