NAME
pthread_barrier_destroy
pthread_barrier_init —
destroy and initialize a barrier object
SYNOPSIS
#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);
DESCRIPTION
The pthread_barrier_destroy () function
shall destroy the barrier referenced by barrier and
release any resources used by the barrier. The effect of subsequent use of
the barrier is undefined until the barrier is reinitialized by another call
to pthread_barrier_init (). An implementation may
use this function to set barrier to an invalid value. The
results are undefined if pthread_barrier_destroy ()
is called when any thread is blocked on the barrier, or if this function is
called with an uninitialized barrier.
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(3) 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(3) 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(3) is undefined.
RETURN VALUE
Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error.
ERRORS
The pthread_barrier_init () function shall
fail if:
- [EAGAIN]
- The system lacks the necessary resources to initialize another barrier.
- [EINVAL]
- The value specified by count is equal to zero.
- [ENOMEM]
- Insufficient memory exists to initialize the barrier.
These functions shall not return an error code of [EINTR].
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
If an implementation detects that the value specified by the
barrier argument to
pthread_barrier_destroy () does not refer to an
initialized barrier object, it is recommended that the function should fail
and report an [EINVAL] error.
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(3) 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.
FUTURE DIRECTIONS
None.
SEE ALSO
XBD <pthread.h>
CHANGE HISTORY
First released in Issue 6. Derived from IEEE Std 1003.1j-2000.
Issue 7
The pthread_barrier_destroy () and
pthread_barrier_init () functions are moved from the
Barriers option to the Base.
The [EINVAL] error for an uninitialized barrier object and an uninitialized barrier attributes object is removed; this condition results in undefined behavior.
The [EBUSY] error for a barrier that is in use or an already initialized barrier object is removed; this condition results in undefined behavior.