Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

pthread_cond_wait(3) [osf1 man page]

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)

Check Out this Related Man Page

tis_cond_timedwait(3)					     Library Functions Manual					     tis_cond_timedwait(3)

NAME
tis_cond_timedwait - Causes a thread to wait for the specified condition variable to be signaled or broadcast, such that it will awake after a specified period of time. LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <tis.h> int tis_cond_timedwait( pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec *abstime); STANDARDS
None PARAMETERS
Condition variable that the calling thread waits on. Mutex associated with the condition variable specified in cond. Absolute time at which the wait expires, if the condition has not been signaled or broadcast. See the tis_get_expiration(3) routine, which is used to obtain a value for this argument. The abstime argument is specified in Universal Coordinated Time (UTC). In the UTC-based model, time is represented as seconds since the Epoch. The Epoch is defined as the time 0 hours, 0 minutes, 0 seconds, January 1st, 1970 UTC. Seconds since the Epoch is a value inter- preted as the number of seconds between a specified time and the Epoch. DESCRIPTION
If threads are not present, this function is equivalent to sleep(3). This routine causes a thread to wait until one of the following occurs: The specified condition variable is signaled or broadcast. The current system clock time is greater than or equal to the time specified by the abstime argument. This routine is identical to tis_cond_wait(3), except that this routine can return before a condition variable is signaled or broadcast; specifically, when the specified time expires. For more information, see the tis_cond_wait(3) description. This routine automatically releases the mutex and causes the calling thread to wait on the condition. When the thread regains control after calling tis_cond_timedwait(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 requires the mutex (blocking if necessary) before the cleanup handlers are run (or before the excep- tion is raised). If the current time equals or exceeds the expiration time, this routine returns immediately, releasing and reacquiring the mutex. It might cause the calling thread to yield (see the sched_yield(3) description). Your code should check the return status whenever this routine returns and take the appropriate action. Otherwise, waiting on the condition variable can become a nonblocking loop. 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. 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, mutex, or abstime is invalid, or: Different mutexes are supplied for concurrent tis_cond_timedwait(3) or tis_cond_wait(3) 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 variable. The time speci- fied by abstime expired. ERRORS
None RELATED INFORMATION
Functions: tis_cond_broadcast(3), tis_cond_destroy(3), tis_cond_init(3), tis_cond_signal(3), tis_cond_wait(3), tis_get_expiration(3) Manuals: Guide to DECthreads and Programmer's Guide delim off tis_cond_timedwait(3)
Man Page