1*062c5bc4SJason Schmidlapp /*
2*062c5bc4SJason Schmidlapp * pthread_barrier_wait.c
3*062c5bc4SJason Schmidlapp *
4*062c5bc4SJason Schmidlapp * Description:
5*062c5bc4SJason Schmidlapp * This translation unit implements barrier primitives.
6*062c5bc4SJason Schmidlapp *
7*062c5bc4SJason Schmidlapp * --------------------------------------------------------------------------
8*062c5bc4SJason Schmidlapp *
9*062c5bc4SJason Schmidlapp * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
10*062c5bc4SJason Schmidlapp * Copyright(C) 2008 Jason Schmidlapp
11*062c5bc4SJason Schmidlapp *
12*062c5bc4SJason Schmidlapp * Contact Email: jschmidlapp@users.sourceforge.net
13*062c5bc4SJason Schmidlapp *
14*062c5bc4SJason Schmidlapp *
15*062c5bc4SJason Schmidlapp * Based upon Pthreads-win32 - POSIX Threads Library for Win32
16*062c5bc4SJason Schmidlapp * Copyright(C) 1998 John E. Bossom
17*062c5bc4SJason Schmidlapp * Copyright(C) 1999,2005 Pthreads-win32 contributors
18*062c5bc4SJason Schmidlapp *
19*062c5bc4SJason Schmidlapp * Contact Email: rpj@callisto.canberra.edu.au
20*062c5bc4SJason Schmidlapp *
21*062c5bc4SJason Schmidlapp * The original list of contributors to the Pthreads-win32 project
22*062c5bc4SJason Schmidlapp * is contained in the file CONTRIBUTORS.ptw32 included with the
23*062c5bc4SJason Schmidlapp * source code distribution. The list can also be seen at the
24*062c5bc4SJason Schmidlapp * following World Wide Web location:
25*062c5bc4SJason Schmidlapp * http://sources.redhat.com/pthreads-win32/contributors.html
26*062c5bc4SJason Schmidlapp *
27*062c5bc4SJason Schmidlapp * This library is free software; you can redistribute it and/or
28*062c5bc4SJason Schmidlapp * modify it under the terms of the GNU Lesser General Public
29*062c5bc4SJason Schmidlapp * License as published by the Free Software Foundation; either
30*062c5bc4SJason Schmidlapp * version 2 of the License, or (at your option) any later version.
31*062c5bc4SJason Schmidlapp *
32*062c5bc4SJason Schmidlapp * This library is distributed in the hope that it will be useful,
33*062c5bc4SJason Schmidlapp * but WITHOUT ANY WARRANTY; without even the implied warranty of
34*062c5bc4SJason Schmidlapp * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
35*062c5bc4SJason Schmidlapp * Lesser General Public License for more details.
36*062c5bc4SJason Schmidlapp *
37*062c5bc4SJason Schmidlapp * You should have received a copy of the GNU Lesser General Public
38*062c5bc4SJason Schmidlapp * License along with this library in the file COPYING.LIB;
39*062c5bc4SJason Schmidlapp * if not, write to the Free Software Foundation, Inc.,
40*062c5bc4SJason Schmidlapp * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
41*062c5bc4SJason Schmidlapp */
42*062c5bc4SJason Schmidlapp
43*062c5bc4SJason Schmidlapp #include "pthread.h"
44*062c5bc4SJason Schmidlapp #include "implement.h"
45*062c5bc4SJason Schmidlapp
46*062c5bc4SJason Schmidlapp
47*062c5bc4SJason Schmidlapp int
pthread_barrier_wait(pthread_barrier_t * barrier)48*062c5bc4SJason Schmidlapp pthread_barrier_wait (pthread_barrier_t * barrier)
49*062c5bc4SJason Schmidlapp {
50*062c5bc4SJason Schmidlapp int result;
51*062c5bc4SJason Schmidlapp int step;
52*062c5bc4SJason Schmidlapp pthread_barrier_t b;
53*062c5bc4SJason Schmidlapp
54*062c5bc4SJason Schmidlapp if (barrier == NULL || *barrier == (pthread_barrier_t) PTE_OBJECT_INVALID)
55*062c5bc4SJason Schmidlapp {
56*062c5bc4SJason Schmidlapp return EINVAL;
57*062c5bc4SJason Schmidlapp }
58*062c5bc4SJason Schmidlapp
59*062c5bc4SJason Schmidlapp b = *barrier;
60*062c5bc4SJason Schmidlapp step = b->iStep;
61*062c5bc4SJason Schmidlapp
62*062c5bc4SJason Schmidlapp if (0 == PTE_ATOMIC_DECREMENT ((int *) &(b->nCurrentBarrierHeight)))
63*062c5bc4SJason Schmidlapp {
64*062c5bc4SJason Schmidlapp /* Must be done before posting the semaphore. */
65*062c5bc4SJason Schmidlapp b->nCurrentBarrierHeight = b->nInitialBarrierHeight;
66*062c5bc4SJason Schmidlapp
67*062c5bc4SJason Schmidlapp /*
68*062c5bc4SJason Schmidlapp * There is no race condition between the semaphore wait and post
69*062c5bc4SJason Schmidlapp * because we are using two alternating semas and all threads have
70*062c5bc4SJason Schmidlapp * entered barrier_wait and checked nCurrentBarrierHeight before this
71*062c5bc4SJason Schmidlapp * barrier's sema can be posted. Any threads that have not quite
72*062c5bc4SJason Schmidlapp * entered sem_wait below when the multiple_post has completed
73*062c5bc4SJason Schmidlapp * will nevertheless continue through the semaphore (barrier)
74*062c5bc4SJason Schmidlapp * and will not be left stranded.
75*062c5bc4SJason Schmidlapp */
76*062c5bc4SJason Schmidlapp result = (b->nInitialBarrierHeight > 1
77*062c5bc4SJason Schmidlapp ? sem_post_multiple (&(b->semBarrierBreeched[step]),
78*062c5bc4SJason Schmidlapp b->nInitialBarrierHeight - 1) : 0);
79*062c5bc4SJason Schmidlapp }
80*062c5bc4SJason Schmidlapp else
81*062c5bc4SJason Schmidlapp {
82*062c5bc4SJason Schmidlapp /*
83*062c5bc4SJason Schmidlapp * Use the non-cancelable version of sem_wait().
84*062c5bc4SJason Schmidlapp */
85*062c5bc4SJason Schmidlapp result = sem_wait (&(b->semBarrierBreeched[step]));
86*062c5bc4SJason Schmidlapp // result = sem_wait_nocancel (&(b->semBarrierBreeched[step]));
87*062c5bc4SJason Schmidlapp }
88*062c5bc4SJason Schmidlapp
89*062c5bc4SJason Schmidlapp /*
90*062c5bc4SJason Schmidlapp * The first thread across will be the PTHREAD_BARRIER_SERIAL_THREAD.
91*062c5bc4SJason Schmidlapp * This also sets up the alternate semaphore as the next barrier.
92*062c5bc4SJason Schmidlapp */
93*062c5bc4SJason Schmidlapp if (0 == result)
94*062c5bc4SJason Schmidlapp {
95*062c5bc4SJason Schmidlapp result = (step ==
96*062c5bc4SJason Schmidlapp PTE_ATOMIC_COMPARE_EXCHANGE (& (b->iStep),(1L - step),step) ?
97*062c5bc4SJason Schmidlapp PTHREAD_BARRIER_SERIAL_THREAD : 0);
98*062c5bc4SJason Schmidlapp }
99*062c5bc4SJason Schmidlapp
100*062c5bc4SJason Schmidlapp return (result);
101*062c5bc4SJason Schmidlapp }
102