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/**
* @file
*
* @brief Lock a Semaphore
* @ingroup POSIX_SEMAPHORE
*/
/*
* COPYRIGHT (c) 1989-2008.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/posix/semaphoreimpl.h>
int sem_trywait( sem_t *_sem )
{
Sem_Control *sem;
Thread_queue_Context queue_context;
ISR_Level level;
unsigned int count;
POSIX_SEMAPHORE_VALIDATE_OBJECT( _sem );
sem = _Sem_Get( &_sem->_Semaphore );
_Thread_queue_Context_initialize( &queue_context );
_Thread_queue_Context_ISR_disable( &queue_context, level );
_Sem_Queue_acquire_critical( sem, &queue_context );
count = sem->count;
if ( RTEMS_PREDICT_TRUE( count > 0 ) ) {
sem->count = count - 1;
_Sem_Queue_release( sem, level, &queue_context );
return 0;
} else {
_Sem_Queue_release( sem, level, &queue_context );
rtems_set_errno_and_return_minus_one( EAGAIN );
}
}
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