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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)
*
* -------------------------------------------------------------
*
* --------------------------------------------------------------------------
*
* Pthreads4w - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999-2018, Pthreads4w contributors
*
* Homepage: https://sourceforge.net/projects/pthreads4w/
*
* 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:
* https://sourceforge.net/p/pthreads4w/wiki/Contributors/
*
* This file is part of Pthreads4w.
*
* Pthreads4w is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Pthreads4w 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Pthreads4w. If not, see <http://www.gnu.org/licenses/>. *
*/
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include "pthread.h"
#include "semaphore.h"
#include "implement.h"
static void PTW32_CDECL
ptw32_sem_wait_cleanup(void * sem)
{
sem_t s = (sem_t) sem;
ptw32_mcs_local_node_t node;
ptw32_mcs_lock_acquire(&s->lock, &node);
/*
* If sema is destroyed do nothing, otherwise:-
* If the sema is posted between us being canceled and us locking
* the sema again above then we need to consume that post but cancel
* anyway. If we don't get the semaphore we indicate that we're no
* longer waiting.
*/
if (*((sem_t *)sem) != NULL && !(WaitForSingleObject(s->sem, 0) == WAIT_OBJECT_0))
{
++s->value;
#if defined(NEED_SEM)
if (s->value > 0)
{
s->leftToUnblock = 0;
}
#else
/*
* Don't release the W32 sema, it doesn't need adjustment
* because it doesn't record the number of waiters.
*/
#endif /* NEED_SEM */
}
ptw32_mcs_lock_release(&node);
}
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.
*
* ------------------------------------------------------
*/
{
ptw32_mcs_local_node_t node;
int v;
int result = 0;
sem_t s = *sem;
pthread_testcancel();
ptw32_mcs_lock_acquire(&s->lock, &node);
v = --s->value;
ptw32_mcs_lock_release(&node);
if (v < 0)
{
#if defined(PTW32_CONFIG_MSVC7)
#pragma inline_depth(0)
#endif
/* Must wait */
pthread_cleanup_push(ptw32_sem_wait_cleanup, (void *) s);
result = pthreadCancelableWait (s->sem);
/* Cleanup if we're canceled or on any other error */
pthread_cleanup_pop(result);
#if defined(PTW32_CONFIG_MSVC7)
#pragma inline_depth()
#endif
}
#if defined(NEED_SEM)
if (!result)
{
ptw32_mcs_lock_acquire(&s->lock, &node);
if (s->leftToUnblock > 0)
{
--s->leftToUnblock;
SetEvent(s->sem);
}
ptw32_mcs_lock_release(&node);
}
#endif /* NEED_SEM */
if (result != 0)
{
PTW32_SET_ERRNO(result);
return -1;
}
return 0;
} /* sem_wait */
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