pthread_cond_signal(3T)                             pthread_cond_signal(3T)
                               Pthread Library

 NAME
      pthread_cond_signal(), pthread_cond_broadcast() - unblock one or all
      threads waiting on a condition variable.

 SYNOPSIS
      #include <pthread.h>

      int pthread_cond_signal(
         pthread_cond_t *cond
      );

      int pthread_cond_broadcast(
         pthread_cond_t *cond
      );

 PARAMETERS
           cond      Pointer to the condition variable to be signaled or
                     broadcast.

 DESCRIPTION
      The pthread_cond_signal() function is used to wake-up one of the
      threads that are waiting for the occurrence of a condition associated
      with condition variable cond.  If there are no threads blocked on
      cond, this function has no effect.  If more than one thread is blocked
      on cond, the scheduling policy determines which thread is unblocked.
      It is possible that more than one thread can be unblocked due to a
      spurious wakeup.

      The pthread_cond_broadcast() function is used to wake-up all threads
      that are waiting for the occurrence of a condition associated with the
      condition variable cond.  If there are no threads blocked on cond,
      this function has no effect.  If more than one thread is blocked on
      cond, the scheduling policy determines the order in which threads are
      unblocked.

      The condition variabled denoted by cond must have been dynamically
      initialized by a call to pthread_cond_init() or statically initialized
      with the macro PTHREAD_COND_INITIALIZER.

      An unblocked thread will reacquire the mutex it held when it started
      the condition wait before returning from pthread_cond_wait() or
      pthread_cond_timedwait().  The threads that are unblocked contend for
      the mutex according to their scheduling policy and priority.

      The pthread_cond_signal() or pthread_cond_broadcast() functions can be
      called by a thread whether or not it currently owns the condition
      variable's associated mutex.  For predictable scheduling behavior and
      to prevent lost wake-ups, the mutex should be held when signaling a
      condition variable.

    Usage

 Hewlett-Packard Company            - 1 -  HP-UX Release 11.00: October 1997

 pthread_cond_signal(3T)                             pthread_cond_signal(3T)
                               Pthread Library

      When using condition variables, there is a boolean predicate
      associated with each condition wait.  If this predicate is false, the
      thread should do a condition wait.  Spurious wakeups may occur when
      waiting on a condition variable.  Because the return values from
      pthread_cond_wait() and pthread_cond_timedwait() do not imply anything
      about the value of this predicate, the predicate should always be re-
      evaluated.

      Applications using condition variables typically acquire a mutex and
      enter a loop which checks the predicate.  Depending on the value of
      the predicate, the thread either breaks out of the loop or waits on
      the condition.  On return from the condition wait, the predicate is
      re-evaluated.

 RETURN VALUE
      Upon successful completion, pthread_cond_signal() and
      pthread_cond_broadcast() return zero. Otherwise, an error number is
      returned to indicate the error (the errno variable is not set).

 ERRORS
      For each of the following conditions, if the condition is detected,
      the pthread_cond_signal() and pthread_cond_broadcast() functions
      return the corresponding error number:

           [EINVAL]       cond is not a valid condition variable.

           [EFAULT]       cond parameter points to an illegal address.

 AUTHOR
      pthread_cond_signal() and pthread_cond_broadcast() were derived from
      the IEEE POSIX P1003.1c standard.

 SEE ALSO
      pthread_cond_init(3T), pthread_cond_wait(3T).

 STANDARDS CONFORMANCE
      pthread_cond_signal(): POSIX 1003.1c.
      pthread_cond_broadcast(): POSIX 1003.1c.