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pthread_cond_signal(3)


NAME

  pthread_cond_signal - Wakes at least one thread that is waiting on the
  specified condition variable


SYNOPSIS

  #include <pthread.h>

  int pthread_cond_signal(
	  pthread_cond_t *cond );


LIBRARY

  DECthreads POSIX 1003.1c Library (libpthread.so)


STANDARDS

  Interfaces documented on this reference page conform to industry standards
  as follows:

  IEEE Std 1003.1c-1995, POSIX System Application Program Interface


PARAMETERS

  cond
      Condition variable to be signaled.


DESCRIPTION

  This routine unblocks at least one thread waiting on the specified
  condition variable cond.  Calling this routine implies that data guarded by
  the associated mutex has changed, thus it might be possible for one of the
  waiting threads to proceed.  In general, only one thread will be released.

  If no threads are waiting on the specified condition variable, this routine
  takes no action. The signal does not propagate to the next condition
  variable wait.

  This routine should be called when any thread waiting on the specified
  condition variable might find its predicate true, but only one thread
  should proceed. If more than one thread can proceed, or if any of the
  threads would not be able to proceed, then you must use
  pthread_cond_broadcast(3).

  The scheduling policy determines which thread is awakened. For policies
  SCHED_FIFO and SCHED_RR, a blocked thread is chosen in priority order,
  using first-in/first-out (FIFO) within priorities.

  If the calling thread holds the lock to the target condition variable's
  associated mutex while setting the variable's wait predicate, that thread
  can call pthread_cond_signal(3) to signal the variable even after releasing
  the lock on that mutex. However, for more predictable scheduling behavior,
  call pthread_cond_signal(3) before releasing the target condition
  variable's associated mutex.


RETURN VALUES

  If an error condition occurs, this routine returns an integer value
  indicating the type of error. Possible return values are as follows:

  0   Successful completion.

  [EINVAL]
      The value specified by cond is not a valid condition variable.


ERRORS

  None


SEE ALSO

  Functions: pthread_cond_broadcast(3), pthread_cond_destroy(3),
  pthread_cond_init(3), pthread_cond_timedwait(3), pthread_cond_wait(3)

  Manuals: Guide to DECthreads and Programmer's Guide

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