pthread_condtimedwait.c

/****************************************************************************
 * sched/pthread_condtimedwait.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 <nuttx/compiler.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>
#include <time.h>
#include <errno.h>
#include <wdog.h>
#include <debug.h>
#include "os_internal.h"
#include "pthread_internal.h"
#include "clock_internal.h"

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

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

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

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

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

/****************************************************************************
 * Function:  pthread_condtimedout
 *
 * Description:
 *   This function is called if the timeout elapses before
 *   the condition is signaled.
 *
 * Parameters:
 *   argc  - the number of arguments (should be 2)
 *   pid   - the task ID of the task to wakeup
 *   signo - The signal to use to wake up the task
 *
 * Return Value:
 *   None
 *
 * Assumptions:
 *
 ****************************************************************************/

static void pthread_condtimedout(int argc, uint32 pid, uint32 signo)
{
#ifdef CONFIG_CAN_PASS_STRUCTS
  union sigval value;

  /* Send the specified signal to the specified task. */

  value.sival_ptr = NULL;
  (void)sigqueue((int)pid, (int)signo, value);
#else
  (void)sigqueue((int)pid, (int)signo, NULL);
#endif
}

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

/****************************************************************************
 * Function:  pthread_cond_timedwait
 *
 * Description:
 *   A thread can perform a timed wait on a condition variable.
 *
 * Parameters:
 *   cond   - the condition variable to wait on
 *   mutex   - the mutex that protects the condition variable
 *   abstime - wait until this absolute time
 *
 * Return Value:
 *   OK (0) on success; ERROR (-1) on failure with errno
 *   set appropriately.
 *
 * Assumptions:
 *   Timing is of resolution 1 msec, with +/-1 millisecond
 *   accuracy.
 *
 ****************************************************************************/

int pthread_cond_timedwait(FAR pthread_cond_t *cond, FAR pthread_mutex_t *mutex,
                           FAR const struct timespec *abstime)
{
  WDOG_ID         wdog;
  int             ticks;
  int             mypid = (int)getpid();
  irqstate_t      int_state;
  int             ret = OK;
  int             status;

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

  /* 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 != mypid)
    {
      ret = EPERM;
    }

  /* If no wait time is provided, this function degenerates to
   * the same behavior as pthread_cond_wait().
   */

  else if (!abstime)
    {
      ret = pthread_cond_wait(cond, mutex);
    }

  else
    {
      /* Create a watchdog */

      wdog = wd_create();
      if (!wdog)
        {
          ret = EINVAL;
        }
      else
        {
          sdbg("Give up mutex...\n");

          /* We must disable pre-emption and interrupts here so that
           * the time stays valid until the wait begins.   This adds
           * complexity because we assure that interrupts and
           * pre-emption are re-enabled correctly.
           */

          sched_lock();
          int_state = irqsave();

          /* Convert the timespec to clock ticks.  We must disable pre-emption
           * here so that this time stays valid until the wait begins.
           */

          ret = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
          if (ret)
            {
              /* Restore interrupts  (pre-emption will be enabled when
               * we fall through the if/then/else
               */

              irqrestore(int_state);
            }
          else
            {
              /* Check the absolute time to wait.  If it is now or in the past, then
               * just return with the timedout condition.
               */

              if (ticks <= 0)
                {
                  /* Restore interrupts and indicate that we have already timed out.
                   * (pre-emption will be enabled when we fall through the
                   * if/then/else
                   */

                  irqrestore(int_state);
                  ret = ETIMEDOUT;
                }
              else
                {
                  /* Give up the mutex */

                  mutex->pid = 0;
                  ret = pthread_givesemaphore((sem_t*)&mutex->sem);
                  if (ret)
                    {
                      /* Restore interrupts  (pre-emption will be enabled when
                       * we fall through the if/then/else)
                       */

                      irqrestore(int_state);
                    }
                  else
                    {
                      /* Start the watchdog */

                      wd_start(wdog, ticks, (wdentry_t)pthread_condtimedout,
                               2, (uint32)mypid, (uint32)SIGCONDTIMEDOUT);

                      /* Take the condition semaphore.  Do not restore interrupts
                       * until we return from the wait.  This is necessary to
                       * make sure that the watchdog timer and the condition wait
                       * are started atomically.
                       */

                      status = sem_wait((sem_t*)&cond->sem);

                      /* Did we get the condition semaphore. */

                      if (status != OK)
                        {
                          /* NO.. Handle the special case where the semaphore wait was
                           * awakened by the receipt of a signal -- presumably the
                           * signal posted by pthread_condtimedout().
                           */

                          if (*get_errno_ptr() == EINTR)
                            {
                              sdbg("Timedout!\n");
                              ret = ETIMEDOUT;
                            }
                          else
                            {
                              ret = EINVAL;
                            }
                        }

                      /* The interrupts stay disabled until after we sample the errno.
                       * This is because when debug is enabled and the console is used
                       * for debug output, then the errno can be altered by interrupt
                       * handling! (bad)
                       */

                      irqrestore(int_state);
                    }

                  /* Reacquire the mutex (retaining the ret). */

                  sdbg("Re-locking...\n");
                  status = pthread_takesemaphore((sem_t*)&mutex->sem);
                  if (!status)
                    {
                      mutex->pid = mypid;
                    }
                  else if (!ret)
                    {
                      ret = status;
                    }
                }

              /* Re-enable pre-emption (It is expected that interrupts
               * have already been re-enabled in the above logic)
               */

              sched_unlock();
            }

          /* We no longer need the watchdog */

          wd_delete(wdog);
        }
    }

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