Synchronize participating threads at the barrier


#include <sync.h>

int pthread_barrier_wait( pthread_barrier_t * barrier );


A pointer to the pthread_barrier_t object that you want to use to synchronize the threads. You must initialize the barrier by calling pthread_barrier_init() before calling pthread_barrier_wait().



Use the -l c option to qcc to link against this library. This library is usually included automatically.


The pthread_barrier_wait() function synchronizes participating threads at the barrier referenced by barrier. The calling thread blocks—that is, it doesn't return from pthread_barrier_wait()—until the required number of threads have called pthread_barrier_wait(), specifying the barrier.

When the required number of threads have called pthread_barrier_wait() specifying the barrier, the function returns PTHREAD_BARRIER_SERIAL_THREAD to one arbitrarily chosen thread, and zero to each of the remaining threads. At this point, the barrier is reset to the state it occupied as a result of the most recent pthread_barrier_init() function that referenced it.

The constant PTHREAD_BARRIER_SERIAL_THREAD is defined in <pthread.h>, and its value is distinct from any other value that pthread_barrier_wait() returns.

If a signal is delivered to a thread blocked on a barrier, on return from the signal handler, the thread resumes waiting at the barrier as if it hadn't been interrupted.


PTHREAD_BARRIER_SERIAL_THREAD to a single (arbitrary) thread synchronized at the barrier, and zero to each of the other threads; otherwise, pthread_barrier_wait() returns an error number:

The barrier argument isn't initialized.


POSIX 1003.1

Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes