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FreeBSD 11.0 - man page for pthread_barrier_wait (freebsd section 3)

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

pthread_barrier_destroy, pthread_barrier_init, pthread_barrier_wait -- destroy, initialize or wait on a barrier object
POSIX Threads Library (libpthread, -lpthread)
#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);
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.
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.
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.
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.
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.
February 19, 2004 BSD

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