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/*
* -------------------------------------------------------------
*
* Module: sem_wait.c
*
* Purpose:
* Semaphores aren't actually part of the PThreads standard.
* They are defined by the POSIX Standard:
*
* POSIX 1003.1b-1993 (POSIX.1b)
*
* -------------------------------------------------------------
*
* --------------------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2003 Pthreads-win32 contributors
*
* Contact Email: rpj@callisto.canberra.edu.au
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* http://sources.redhat.com/pthreads-win32/contributors.html
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library in the file COPYING.LIB;
* if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "pthread.h"
#include "semaphore.h"
#include "implement.h"
static inline void
ptw32_sem_wait_cleanup(void * sem)
{
sem_t s = (sem_t) sem;
if (pthread_mutex_lock (&s->lock) == 0)
{
s->value++;
ReleaseSemaphore(s->sem, 1, 0);
(void) pthread_mutex_unlock (&s->lock);
}
}
int
sem_wait (sem_t * sem)
/*
* ------------------------------------------------------
* DOCPUBLIC
* This function waits on a semaphore.
*
* PARAMETERS
* sem
* pointer to an instance of sem_t
*
* DESCRIPTION
* This function waits on a semaphore. If the
* semaphore value is greater than zero, it decreases
* its value by one. If the semaphore value is zero, then
* the calling thread (or process) is blocked until it can
* successfully decrease the value or until interrupted by
* a signal.
*
* RESULTS
* 0 successfully decreased semaphore,
* -1 failed, error in errno
* ERRNO
* EINVAL 'sem' is not a valid semaphore,
* ENOSYS semaphores are not supported,
* EINTR the function was interrupted by a signal,
* EDEADLK a deadlock condition was detected.
*
* ------------------------------------------------------
*/
{
int result = 0;
sem_t s = *sem;
if (s == NULL)
{
result = EINVAL;
}
else
{
#ifdef NEED_SEM
result = pthreadCancelableWait (s->event);
#else /* NEED_SEM */
if ((result = pthread_mutex_lock (&s->lock)) == 0)
{
int v = --s->value;
(void) pthread_mutex_unlock (&s->lock);
if (v < 0)
{
/* Must wait */
pthread_cleanup_push(ptw32_sem_wait_cleanup, s);
result = pthreadCancelableWait (s->sem);
/*
* Restore the semaphore counters if no longer waiting
* and not taking the semaphore. This will occur if the
* thread is cancelled while waiting, or the wake was
* not the result of a post event given to us.
*/
pthread_cleanup_pop(result);
}
}
#endif /* NEED_SEM */
}
if (result != 0)
{
errno = result;
return -1;
}
#ifdef NEED_SEM
ptw32_decrease_semaphore (sem);
#endif /* NEED_SEM */
return 0;
} /* sem_wait */
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