pthread_barrier(3) - NetBSD Manual Pages

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PTHREAD_BARRIER(3)      NetBSD 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);

     int
     pthread_barrierattr_getpshared(const pthread_barrierattr_t * __restrict attr,
         int * __restrict pshared);

     int
     pthread_barrierattr_setpshared(pthread_barrierattr_t * attr,
         int pshared);


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.

     The pthread_barrierattr_getpshared() function shall obtain the value of
     the process-shared attribute from the attributes object referenced by
     attr.  The pthread_barrierattr_setpshared() function shall set the
     process-shared attribute in an initialized attributes object referenced
     by attr.


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.

     If successful, pthread_barrierattr_getpshared() shall return zero and
     store the value of the process-shared attribute of attr into the object
     referenced by the pshared parameter.  Otherwise, an error number shall be
     returned to indicate the error.

     If successful, pthread_barrierattr_setpshared() shall return zero; Other-
     wise, an error number shall be returned to indicate the error.


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.

     The pthread_barrierattr_setpshared() function and the
     pthread_barrierattr_getpshared() function may fail if:

     [EINVAL]           The value specified by attr 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'').


BUGS

     The pthread_barrierattr_getpshared() and pthread_barrierattr_setpshared()
     functions are hidden by default since only thread shared attributes are
     supported.

NetBSD 8.2                       June 12, 2016                      NetBSD 8.2