pthread_cond_wait(3C)					   Standard C Library Functions 				     pthread_cond_wait(3C)

NAME

       pthread_cond_wait, pthread_cond_timedwait, pthread_cond_reltimedwait_np - wait on a condition

SYNOPSIS

       cc -mt [ flag... ] file... -lpthread [ library... ]
       #include <pthread.h>

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

       int pthread_cond_timedwait(pthread_cond_t *restrict cond,
	    pthread_mutex_t *restrict mutex,
	    const struct timespec *restrict abstime);

       int pthread_cond_reltimedwait_np(pthread_cond_t *cond,
	    pthread_mutex_t *mutex, const struct timespec *reltime);

DESCRIPTION

       The  pthread_cond_wait(), pthread_cond_timedwait(), and pthread_cond_reltimedwait_np() functions are used to block on a condition variable.
       They are called with mutex locked by the calling thread or undefined behavior will result.

       These functions atomically release mutex and cause the calling thread to block on  the  condition  variable  cond.  Atomically  here  means
       ``atomically with respect to access by another  thread to the mutex and then the condition variable." That is, if another thread is able to
       acquire the mutex after the about-to-block thread has released it, then a subsequent call to pthread_cond_signal()  or  pthread_cond_broad-
       cast() in that thread behaves as if it were issued after the about-to-block thread has blocked.

       Upon  successful return, the mutex has been locked and is owned by the calling thread. If mutex is a robust mutex where an owner terminated
       while holding the lock and the state is recoverable, the mutex is acquired even though the function returns an error value.

       When using condition variables there is always a boolean predicate, an invariant, associated with each condition wait  that  must  be  true
       before  the  thread  should  proceed.  Spurious	wakeups  from the pthread_cond_wait(), pthread_cond_timedwait(), or pthread_cond_reltimed-
       wait_np() functions could occur. Since the return from  pthread_cond_wait(),  pthread_cond_timedwait(),	or  pthread_cond_reltimedwait_np()
       does not imply anything about the value of this predicate, the predicate should always be reevaluated.

       The  order  in which blocked threads are awakened by pthread_cond_signal() or pthread_cond_broadcast() is determined by the scheduling pol-
       icy. See pthreads(5).

       The effect of using more than one mutex for concurrent  pthread_cond_wait(),  pthread_cond_timedwait(),	or  pthread_cond_reltimedwait_np()
       operations on the same condition variable will result in undefined behavior.

       A  condition  wait  (whether  timed or not) is a cancellation point. When the cancelability enable state of a thread is set to PTHREAD_CAN-
       CEL_DEFERRED, a side effect of acting upon a cancellation request while in a condition wait is that the mutex is reacquired before  calling
       the first cancellation cleanup handler.

       A  thread  that	has been unblocked because it has been canceled while blocked in a call to pthread_cond_wait() or pthread_cond_timedwait()
       does not consume any condition signal that may be directed concurrently at the condition variable if there are other threads blocked on the
       condition variable.

       The pthread_cond_timedwait() function is the same as pthread_cond_wait() except that an error is returned if the absolute time specified by
       abstime passes (that is, system time equals or exceeds abstime) before the condition cond is signaled or broadcast, or if the absolute time
       specified  by  abstime  has  already  been  passed  at  the  time  of the call. The abstime argument is of type struct timespec, defined in
       time.h(3HEAD). When such time-outs occur, pthread_cond_timedwait() will nonetheless release and reacquire the mutex  referenced	by  mutex.
       The function pthread_cond_timedwait() is also a cancellation point.

       The  pthread_cond_reltimedwait_np()  function  is a non-standard extension provided by the Solaris version of POSIX threads as indicated by
       the ``_np'' (non-portable) suffix. The pthread_cond_reltimedwait_np() function is the same as pthread_cond_timedwait() except that the rel-
       time  argument  specifies  a non-negative time relative to the current system time rather than an absolute time. The reltime argument is of
       type struct timespec, defined in time.h(3HEAD). An error value is returned if the relative time passes (that  is,  system  time	equals	or
       exceeds	the  starting  system  time plus the relative time) before the condition cond is signaled or broadcast.  When such timeouts occur,
       pthread_cond_reltimedwait_np() releases and reacquires the mutex referenced by mutex.  The pthread_cond_reltimedwait_np() function is  also
       a cancellation point.

       If  a  signal is delivered to a thread waiting for a condition variable, upon return from the signal handler the thread resumes waiting for
       the condition variable as if it was not interrupted, or it returns 0 due to spurious wakeup.

RETURN VALUES

       Except in the case of ETIMEDOUT, EOWNERDEAD, or ENOTRECOVERABLE, all of these error checks act as if they were performed immediately at the
       beginning of processing for the function and cause an error return, in effect, prior to modifying the state of the mutex specified by mutex
       or the condition variable specified by cond.

       Upon successful completion, 0 is returned. Otherwise, an error value is returned to indicate the error.

ERRORS

       These functions will fail if:

       EPERM	The mutex type is PTHREAD_MUTEX_ERRORCHECK or the mutex is a robust mutex, and the current thread does not own the mutex.

       The  pthread_cond_timedwait() function will fail if:

       ETIMEDOUT    The absolute time specified by abstime to pthread_cond_timedwait() has passed.

       The pthread_cond_reltimedwait_np() function will fail if:

       EINVAL	    The value specified by reltime is invalid.

       ETIMEDOUT    The relative time specified by reltime to pthread_cond_reltimedwait_np() has passed.

       These functions may fail if:

       EINVAL	 The value specified by cond, mutex, abstime, or reltime is invalid.

       EINVAL	 Different mutexes were supplied for concurrent operations on the same condition variable.

       If  the	mutex  specified  by  mutex  is  a  robust  mutex  (initialized  with  the   robustness   attribute   PTHREAD_MUTEX_ROBUST),   the
       pthread_cond_wait(),  pthread_cond_timedwait(),	and  pthread_cond_reltimedwait_np() functions will, under the specified conditions, return
       the following error values.  For complete information, see the pthread_mutex_lock(3C) and pthread_mutexattr_setrobust(3C) manual pages.

       EOWNERDEAD	  The last owner of this mutex died while holding the mutex, leaving the state it was  protecting  possibly  inconsistent.
			  The mutex is now owned by the caller.

       ENOTRECOVERABLE	  The mutex was protecting state that has now been left irrecoverable. The mutex has not been acquired.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       pthread_cond_signal(3C), pthread_cond_broadcast(3C), pthread_mutex_lock(3C), pthread_mutexattr_getrobust(3C), time.h(3HEAD), attributes(5),
       condition(5), pthreads(5), standards(5)

SunOS 5.11							    11 Nov 2008 					     pthread_cond_wait(3C)