px4-firmware/nuttx/sched/pthread_initialize.c

/****************************************************************************
 * sched/pthread_initialize.c
 *
 *   Copyright (C) 2007-2010 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * 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 <nuttx/config.h>

#include <stdint.h>
#include <semaphore.h>
#include <errno.h>

#include "pthread_internal.h"

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

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

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

/* This is the head of a private singly linked list.  It
 * is used to retain information about the spawned threads.
 */

FAR join_t *g_pthread_head = NULL;
FAR join_t *g_pthread_tail = NULL;

/* Mutually exclusive access to this data set is enforced with
 * the following (un-named) semaphore.
 */

sem_t g_join_semaphore;

/* This keys track of the number of global keys that have been
 * allocated.
 */

uint8_t g_pthread_num_keys;

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

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

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

/****************************************************************************
 * Name: pthread_initialize
 *
 * Description:
 *   This is an internal OS function called only at power-up boot time.
 *
 * Parameters:
 *   None
 *
 * Return Value:
 *   None
 *
 * Assumptions:
 *
 ****************************************************************************/

void pthread_initialize(void)
{
  /* Initialize some global variables */

  g_pthread_head          = NULL;
  g_pthread_tail          = NULL;
  g_pthread_num_keys      = 0;

  /* Initialize the join semaphore to one (to support one-at-
   * a-time access to private data sets).
   */

  (void)sem_init(&g_join_semaphore, 0, 1);
}

/****************************************************************************
 * Name: pthread_takesemaphore and pthread_givesemaphore
 *
 * Description:
 *   Support managed access to the private data sets.
 *
 * Parameters:
 *   None
 *
 * Return Value:
 *   0 on success or an ERROR on failure with errno value set to EINVAL.
 *   Note that the errno EINTR is never returned by this function.
 *
 * Assumptions:
 *
 ****************************************************************************/

int pthread_takesemaphore(sem_t *sem)
{
  /* Verify input parameters */

  if (sem)
    {
      /* Take the semaphore */

      while (sem_wait(sem) != OK)
        {
          /* Handle the special case where the semaphore wait was
           * awakened by the receipt of a signal.
           */

          if (get_errno() != EINTR)
            {
              set_errno(EINVAL);
              return ERROR;
            }
        }
      return OK;
    }
  else
    {
      /* NULL semaphore pointer! */

      set_errno(EINVAL);
      return ERROR;
    }
}

int pthread_givesemaphore(sem_t *sem)
{
  /* Verify input parameters */

  if (sem)
    {
      /* Give the semaphore */

      if (sem_post(sem) == OK)
        {
          return OK;
        }
      else
        {
          /* sem_post() reported an error */

          set_errno(EINVAL);
          return ERROR;
        }
    }
  else
    {
      /* NULL semaphore pointer! */

      set_errno(EINVAL);
      return ERROR;
    }
}