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pthread_barrier_wait(3) [freebsd man page]

PTHREAD_BARRIER(3)					   BSD Library Functions Manual 					PTHREAD_BARRIER(3)

NAME
pthread_barrier_destroy, pthread_barrier_init, pthread_barrier_wait -- destroy, initialize or wait on a barrier object LIBRARY
POSIX Threads Library (libpthread, -lpthread) SYNOPSIS
#include <pthread.h> int pthread_barrier_destroy(pthread_barrier_t *barrier); int pthread_barrier_init(pthread_barrier_t *barrier, const pthread_barrierattr_t *attr, unsigned count); int pthread_barrier_wait(pthread_barrier_t *barrier); DESCRIPTION
The pthread_barrier_init() function will initialize barrier with attributes specified in attr, or if it is NULL, with default attributes. The number of threads that must call pthread_barrier_wait() before any of the waiting threads can be released is specified by count. The pthread_barrier_destroy() function will destroy barrier and release any resources that may have been allocated on its behalf. The pthread_barrier_wait() function will synchronize calling threads at barrier. The threads will be blocked from making further progress until a sufficient number of threads calls this function. The number of threads that must call it before any of them will be released is determined by the count argument to pthread_barrier_init(). Once the threads have been released the barrier will be reset. IMPLEMENTATION NOTES
In both N:M Threading Library (libkse, -lkse) and 1:1 Threading Library (libthr, -lthr) the PTHREAD_BARRIER_SERIAL_THREAD return value will always be returned by the last thread to reach the barrier. RETURN VALUES
If successful, both pthread_barrier_destroy() and pthread_barrier_init() will return zero. Otherwise, an error number will be returned to indicate the error. If the call to pthread_barrier_wait() is successful, all but one of the threads will return zero. That one thread will return PTHREAD_BARRIER_SERIAL_THREAD. Otherwise, an error number will be returned to indicate the error. None of these functions will return EINTR. ERRORS
The pthread_barrier_destroy() function will fail if: [EBUSY] An attempt was made to destroy barrier while it was in use. The pthread_barrier_destroy() and pthread_barrier_wait() functions may fail if: [EINVAL] The value specified by barrier is invalid. The pthread_barrier_init() function will fail if: [EAGAIN] The system lacks resources, other than memory, to initialize barrier. [EINVAL] The count argument is less than 1. [ENOMEM] Insufficient memory to initialize barrier. SEE ALSO
pthread_barrierattr(3) HISTORY
The pthread_barrier_destroy(), pthread_barrier_init() and pthread_barrier_wait() functions first appeared in N:M Threading Library (libkse, -lkse) in FreeBSD 5.2, and in 1:1 Threading Library (libthr, -lthr) in FreeBSD 5.3. BSD
February 19, 2004 BSD

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PTHREAD_BARRIER(3)					   BSD Library Functions Manual 					PTHREAD_BARRIER(3)

NAME
pthread_barrier -- barrier interface LIBRARY
POSIX Threads Library (libpthread, -lpthread) SYNOPSIS
#include <pthread.h> int pthread_barrier_init(pthread_barrier_t * restrict barrier, const pthread_barrierattr_t * restrict attr, unsigned int count); int pthread_barrier_destroy(pthread_barrier_t *barrier); int pthread_barrier_wait(pthread_barrier_t *barrier); DESCRIPTION
The pthread_barrier_init() function creates a new barrier with attributes attr and count. The count parameter indicates the number of threads which will participate in the barrier. The pthread_barrierattr_init(3) function may be used to specify the attributes supplied in attr. If attr is NULL, the default attributes are used. Barriers are most commonly used in the decomposition of parallel loops. The pthread_barrier_destroy() function causes the resources allocated to barrier to be released. No threads should be blocked on barrier. The pthread_barrier_wait() function causes the current thread to wait on the barrier specified. Once as many threads as specified by the count parameter to the corresponding pthread_barrier_init() call have called pthread_barrier_wait(), all threads will wake up, return from their respective pthread_barrier_wait() calls and continue execution. RETURN VALUES
If successful, pthread_barrier_init() will return zero and put the new barrier id into barrier, otherwise an error number will be returned to indicate the error. If successful, pthread_barrier_destroy() will return zero. Otherwise an error value will be returned. If successful, pthread_barrier_wait() will return zero for all waiting threads except for one. One thread will receive status PTHREAD_BARRIER_SERIAL_THREAD, which is intended to indicate that this thread may be used to update shared data. It is the responsibility of this thread to insure the visibility and atomicity of any updates to shared data with respect to the other threads participating in the bar- rier. In the case of failure, an error value will be returned. ERRORS
The pthread_barrier_init() function may fail if: [EINVAL] The value specified by count is zero or attr is invalid. The pthread_barrier_destroy() function may fail if: [EBUSY] The barrier still has active threads associated with it. [EINVAL] The value specified by barrier is invalid. The pthread_barrier_wait() function may fail if: [EINVAL] The value specified by barrier is invalid. SEE ALSO
pthread_barrierattr(3), pthread_cond(3), pthread_mutex(3) STANDARDS
These functions conform to IEEE Std 1003.1-2001 (``POSIX.1''). BSD
July 8, 2010 BSD

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