pthread_cond_wait(3)					     Library Functions Manual					      pthread_cond_wait(3)

NAME

       pthread_cond_wait - Causes a thread to wait for the specified condition variable to be signaled or broadcasted.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int pthread_cond_wait(
			 pthread_cond_t      *cond,
			 pthread_mutex_t     *mutex);

STANDARDS

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

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

PARAMETERS

       Condition variable that the calling thread waits on.  Mutex associated with the condition variable specified in cond.

DESCRIPTION

       This routine causes a thread to wait for the specified condition variable to be signaled or broadcasted.  Each condition corresponds to one
       or more Boolean relations, called a predicate, based on shared data.  The calling thread waits for the data to reach a particular state for
       the  predicate  to  become  true.   However,  the return from this routine does not imply anything about the value of the predicate, and it
       should be reevaluated upon return.

       Call this routine after you have locked the mutex specified in mutex.  The results of this routine are unpredictable  if  this  routine	is
       called without first locking the mutex.

       This  routine  atomically releases the mutex and causes the calling thread to wait on the condition.  When the thread regains control after
       calling pthread_cond_wait(3), the mutex is locked and the thread is the owner.  This is true regardless of why the wait ended.  If  general
       cancelability is enabled, the thread reacquires the mutex (blocking for it if necessary) before the cleanup handlers are run (or before the
       exception is raised).

       A thread that changes the state of storage protected by the mutex in such a way that a predicate associated with a condition variable might
       now  be	true,  must call either pthread_cond_signal(3) or pthread_cond_broadcast(3) for that condition variable.  If neither call is made,
       any thread waiting on the condition variable continues to wait.

       This routine might (with low probability) return when the condition variable has not been signaled or broadcasted.  When this  occurs,  the
       mutex  is reacquired before the routine returns.  To handle this type of situation, enclose each call to this routine in a loop that checks
       the predicate.  The loop provides documentation of your intent and protects against these spurious wakeups,  while  also  allowing  correct
       behavior even if another thread consumes the desired state before the awakened thread runs.

       It is illegal for threads to wait on the same condition variable by specifying different mutexes.

       The only routines which are supported for use with asynchronous cancelability enabled are those which disable asynchronous cancelability.

RETURN VALUES

       If  an  error condition occurs, this routine returns an integer value indicating the type of error.  Possible return values are as follows:
       Successful completion.	The  value  specified  by  cond,  or  mutex  is  invalid,  or:	Different  mutexes  are  supplied  for	concurrent
       pthread_cond_wait(3)  operations  or  pthread_cond_timedwait  operations on the same condition variable, or: The mutex was not owned by the
       calling thread at the time of the call.	DECthreads cannot acquire memory needed to block using a statically  initialized  condition  vari-
       able.

ERRORS

       None

RELATED INFORMATION

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

       Manuals: Guide to DECthreads and Programmer's Guide

       delim off

															      pthread_cond_wait(3)