#include <pthread.h> int pthread_barrier_destroy(pthread_barrier_t *barrier); int pthread_barrier_init(pthread_barrier_t *restrict barrier, const pthread_barrierattr_t *restrict attr, unsigned count);
The pthread_barrier_init() function shall allocate any resources required to use the barrier referenced by barrier and shall initialize the barrier with attributes referenced by attr. If attr is NULL, the default barrier attributes shall be used; the effect is the same as passing the address of a default barrier attributes object. The results are undefined if pthread_barrier_init() is called when any thread is blocked on the barrier (that is, has not returned from the pthread_barrier_wait() call). The results are undefined if a barrier is used without first being initialized. The results are undefined if pthread_barrier_init() is called specifying an already initialized barrier.
The count argument specifies the number of threads that must call pthread_barrier_wait() before any of them successfully return from the call. The value specified by count must be greater than zero.
If the pthread_barrier_init() function fails, the barrier shall not be initialized and the contents of barrier are undefined.
Only the object referenced by barrier may be used for performing synchronization. The result of referring to copies of that object in calls to pthread_barrier_destroy() or pthread_barrier_wait() is undefined.
These functions shall not return an error code of [EINTR].
If an implementation detects that the value specified by the attr argument to pthread_barrier_init() does not refer to an initialized barrier attributes object, it is recommended that the function should fail and report an [EINVAL] error.
If an implementation detects that the value specified by the barrier argument to pthread_barrier_destroy() or pthread_barrier_init() refers to a barrier that is in use (for example, in a pthread_barrier_wait() call) by another thread, or detects that the value specified by the barrier argument to pthread_barrier_init() refers to an already initialized barrier object, it is recommended that the function should fail and report an [EBUSY] error.
The Base Definitions volume of POSIX.1-2008, <pthread.h>
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