pthread_cond_wait.c

pthread source code,you can compile directly

  /*
   * Whether we got here as a result of signal/broadcast or because of
   * timeout on wait or thread cancellation we indicate that we are no
   * longer waiting. The waiter is responsible for adjusting waiters
   * (to)unblock(ed) counts (protected by unblock lock).
   */
  if ((result = pthread_mutex_lock (&(cv->mtxUnblockLock))) != 0)
    {
      *resultPtr = result;
      return;
    }

  if (0 != (nSignalsWasLeft = cv->nWaitersToUnblock))
    {
      --(cv->nWaitersToUnblock);
    }
  else if (INT_MAX / 2 == ++(cv->nWaitersGone))
    {
      /* Use the non-cancellable version of sem_wait() */
      if (ptw32_semwait (&(cv->semBlockLock)) != 0)
	{
	  *resultPtr = errno;
	  /*
	   * This is a fatal error for this CV,
	   * so we deliberately don't unlock
	   * cv->mtxUnblockLock before returning.
	   */
	  return;
	}
      cv->nWaitersBlocked -= cv->nWaitersGone;
      if (sem_post (&(cv->semBlockLock)) != 0)
	{
	  *resultPtr = errno;
	  /*
	   * This is a fatal error for this CV,
	   * so we deliberately don't unlock
	   * cv->mtxUnblockLock before returning.
	   */
	  return;
	}
      cv->nWaitersGone = 0;
    }

  if ((result = pthread_mutex_unlock (&(cv->mtxUnblockLock))) != 0)
    {
      *resultPtr = result;
      return;
    }

  if (1 == nSignalsWasLeft)
    {
      if (sem_post (&(cv->semBlockLock)) != 0)
	{
	  *resultPtr = errno;
	  return;
	}
    }

  /*
   * XSH: Upon successful return, the mutex has been locked and is owned
   * by the calling thread.
   */
  if ((result = pthread_mutex_lock (cleanup_args->mutexPtr)) != 0)
    {
      *resultPtr = result;
    }
}				/* ptw32_cond_wait_cleanup */

static INLINE int
ptw32_cond_timedwait (pthread_cond_t * cond,
		      pthread_mutex_t * mutex, const struct timespec *abstime)
{
  int result = 0;
  pthread_cond_t cv;
  ptw32_cond_wait_cleanup_args_t cleanup_args;

  if (cond == NULL || *cond == NULL)
    {
      return EINVAL;
    }

  /*
   * We do a quick check to see if we need to do more work
   * to initialise a static condition variable. We check
   * again inside the guarded section of ptw32_cond_check_need_init()
   * to avoid race conditions.
   */
  if (*cond == PTHREAD_COND_INITIALIZER)
    {
      result = ptw32_cond_check_need_init (cond);
    }

  if (result != 0 && result != EBUSY)
    {
      return result;
    }

  cv = *cond;

  /* Thread can be cancelled in sem_wait() but this is OK */
  if (sem_wait (&(cv->semBlockLock)) != 0)
    {
      return errno;
    }

  ++(cv->nWaitersBlocked);

  if (sem_post (&(cv->semBlockLock)) != 0)
    {
      return errno;
    }

  /*
   * Setup this waiter cleanup handler
   */
  cleanup_args.mutexPtr = mutex;
  cleanup_args.cv = cv;
  cleanup_args.resultPtr = &result;

#ifdef _MSC_VER
#pragma inline_depth(0)
#endif
  pthread_cleanup_push (ptw32_cond_wait_cleanup, (void *) &cleanup_args);

  /*
   * Now we can release 'mutex' and...
   */
  if ((result = pthread_mutex_unlock (mutex)) == 0)
    {

      /*
       * ...wait to be awakened by
       *              pthread_cond_signal, or
       *              pthread_cond_broadcast, or
       *              timeout, or
       *              thread cancellation
       *
       * Note:
       *
       *      sem_timedwait is a cancellation point,
       *      hence providing the mechanism for making
       *      pthread_cond_wait a cancellation point.
       *      We use the cleanup mechanism to ensure we
       *      re-lock the mutex and adjust (to)unblock(ed) waiters
       *      counts if we are cancelled, timed out or signalled.
       */
      if (sem_timedwait (&(cv->semBlockQueue), abstime) != 0)
	{
	  result = errno;
	}
    }

  /*
   * Always cleanup
   */
  pthread_cleanup_pop (1);
#ifdef _MSC_VER
#pragma inline_depth()
#endif

  /*
   * "result" can be modified by the cleanup handler.
   */
  return result;

}				/* ptw32_cond_timedwait */


int
pthread_cond_wait (pthread_cond_t * cond, pthread_mutex_t * mutex)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function waits on a condition variable until
      *      awakened by a signal or broadcast.
      *
      *      Caller MUST be holding the mutex lock; the
      *      lock is released and the caller is blocked waiting
      *      on 'cond'. When 'cond' is signaled, the mutex
      *      is re-acquired before returning to the caller.
      *
      * PARAMETERS
      *      cond
      *              pointer to an instance of pthread_cond_t
      *
      *      mutex
      *              pointer to an instance of pthread_mutex_t
      *
      *
      * DESCRIPTION
      *      This function waits on a condition variable until
      *      awakened by a signal or broadcast.
      *
      *      NOTES:
      *
      *      1)      The function must be called with 'mutex' LOCKED
      *              by the calling thread, or undefined behaviour
      *              will result.
      *
      *      2)      This routine atomically releases 'mutex' and causes
      *              the calling thread to block on the condition variable.
      *              The blocked thread may be awakened by 
      *                      pthread_cond_signal or 
      *                      pthread_cond_broadcast.
      *
      * Upon successful completion, the 'mutex' has been locked and 
      * is owned by the calling thread.
      *
      *
      * RESULTS
      *              0               caught condition; mutex released,
      *              EINVAL          'cond' or 'mutex' is invalid,
      *              EINVAL          different mutexes for concurrent waits,
      *              EINVAL          mutex is not held by the calling thread,
      *
      * ------------------------------------------------------
      */
{
  /*
   * The NULL abstime arg means INFINITE waiting.
   */
  return (ptw32_cond_timedwait (cond, mutex, NULL));

}				/* pthread_cond_wait */


int
pthread_cond_timedwait (pthread_cond_t * cond,
			pthread_mutex_t * mutex,
			const struct timespec *abstime)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      This function waits on a condition variable either until
      *      awakened by a signal or broadcast; or until the time
      *      specified by abstime passes.
      *
      * PARAMETERS
      *      cond
      *              pointer to an instance of pthread_cond_t
      *
      *      mutex
      *              pointer to an instance of pthread_mutex_t
      *
      *      abstime
      *              pointer to an instance of (const struct timespec)
      *
      *
      * DESCRIPTION
      *      This function waits on a condition variable either until
      *      awakened by a signal or broadcast; or until the time
      *      specified by abstime passes.
      *
      *      NOTES:
      *      1)      The function must be called with 'mutex' LOCKED
      *              by the calling thread, or undefined behaviour
      *              will result.
      *
      *      2)      This routine atomically releases 'mutex' and causes
      *              the calling thread to block on the condition variable.
      *              The blocked thread may be awakened by 
      *                      pthread_cond_signal or 
      *                      pthread_cond_broadcast.
      *
      *
      * RESULTS
      *              0               caught condition; mutex released,
      *              EINVAL          'cond', 'mutex', or abstime is invalid,
      *              EINVAL          different mutexes for concurrent waits,
      *              EINVAL          mutex is not held by the calling thread,
      *              ETIMEDOUT       abstime ellapsed before cond was signaled.
      *
      * ------------------------------------------------------
      */
{
  if (abstime == NULL)
    {
      return EINVAL;
    }

  return (ptw32_cond_timedwait (cond, mutex, abstime));

}				/* pthread_cond_timedwait */