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
POSIX Threads Library (libpthread, -lpthread)
const pthread_barrierattr_t *attr, unsigned count);
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 deter‐
mined by the count argument to pthread_barrier_init(). Once the threads
have been released the barrier will be reset.
In both library “libkse” and library “libthr” 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 indi‐
cate 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
The pthread_barrier_destroy() and pthread_barrier_wait() functions may
[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 ini‐
[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 library “libkse” in
FreeBSD 5.2, and in library “libthr” in FreeBSD 5.3.
BSD February 19, 2004 BSD