cpukit/posix/src/semgetvalue.c


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/**
 * @file
 *
 * @brief Get the Value of a Semaphore
 * @ingroup POSIX_SEMAPHORE
 */

/*
 *  COPYRIGHT (c) 1989-2014.
 *  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 <semaphore.h>

#include <rtems/posix/semaphoreimpl.h>

int sem_getvalue(
  sem_t  *__restrict sem,
  int    *__restrict sval
)
{
  POSIX_Semaphore_Control *the_semaphore;
  ISR_lock_Context         lock_context;

  the_semaphore = _POSIX_Semaphore_Get( sem, &lock_context );

  if ( the_semaphore == NULL ) {
    rtems_set_errno_and_return_minus_one( EINVAL );
  }

  /*
   * Assume a relaxed atomic load of the value on SMP configurations.
   * Thus, there is no need to acquire a lock.
   */
  *sval = _CORE_semaphore_Get_count( &the_semaphore->Semaphore );

  _ISR_lock_ISR_enable( &lock_context );
  return 0;
}