sched/pthread_condwait.c

/****************************************************************************
 * sched/pthread_condwait.c
 *
 *   Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <sched.h>
#include <errno.h>
#include <debug.h>
#include "pthread_internal.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Function:  int pthread_cond_wait
 *
 * Description:
 *   A thread can wait for a condition variable to be
 *  signalled or broadcast.
 *
 * Parameters:
 *   None
 *
 * Return Value:
 *   None
 *
 * Assumptions:
 *
 ****************************************************************************/

int pthread_cond_wait(FAR pthread_cond_t *cond, FAR pthread_mutex_t *mutex)
{
  int ret;

  sdbg("cond=0x%p mutex=0x%p\n", cond, mutex);

  /* Make sure that non-NULL references were provided. */

  if (!cond || !mutex)
    {
      ret = EINVAL;
    }

  /* Make sure that the caller holds the mutex */

  else if (mutex->pid != (int)getpid())
    {
      ret = EPERM;
    }

  else
    {
      /* Give up the mutex */

      sdbg("Give up mutex / take cond\n");

      sched_lock();
      mutex->pid = 0;
      ret = pthread_givesemaphore((sem_t*)&mutex->sem);

      /* Take the semaphore */

      ret |= pthread_takesemaphore((sem_t*)&cond->sem);
      sched_unlock();

      /* Reacquire the mutex */

      sdbg("Reacquire mutex...\n");
      ret |= pthread_takesemaphore((sem_t*)&mutex->sem);
      if (!ret)
        {
          mutex->pid = getpid();;
        }
    }

  sdbg("Returning %d\n", ret);
  return ret;
}