pthread_barrier_wait(3) [linux man page]
PTHREAD_BARRIER_WAIT(P) POSIX Programmer's Manual PTHREAD_BARRIER_WAIT(P) NAME
pthread_barrier_wait - synchronize at a barrier (ADVANCED REALTIME THREADS) SYNOPSIS
#include <pthread.h> int pthread_barrier_wait(pthread_barrier_t *barrier); DESCRIPTION
The pthread_barrier_wait() function shall synchronize participating threads at the barrier referenced by barrier. The calling thread shall block 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 constant PTHREAD_BARRIER_SERIAL_THREAD shall be returned to one unspecified thread and zero shall be returned to each of the remaining threads. At this point, the barrier shall be reset to the state it had 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 shall be distinct from any other value returned by pthread_barrier_wait(). The results are undefined if this function is called with an uninitialized barrier. If a signal is delivered to a thread blocked on a barrier, upon return from the signal handler the thread shall resume waiting at the bar- rier if the barrier wait has not completed (that is, if the required number of threads have not arrived at the barrier during the execution of the signal handler); otherwise, the thread shall continue as normal from the completed barrier wait. Until the thread in the signal han- dler returns from it, it is unspecified whether other threads may proceed past the barrier once they have all reached it. A thread that has blocked on a barrier shall not prevent any unblocked thread that is eligible to use the same processing resources from eventually making forward progress in its execution. Eligibility for processing resources shall be determined by the scheduling policy. RETURN VALUE
Upon successful completion, the pthread_barrier_wait() function shall return PTHREAD_BARRIER_SERIAL_THREAD for a single (arbitrary) thread synchronized at the barrier and zero for each of the other threads. Otherwise, an error number shall be returned to indicate the error. ERRORS
The pthread_barrier_wait() function may fail if: EINVAL The value specified by barrier does not refer to an initialized barrier object. This function shall not return an error code of [EINTR]. The following sections are informative. EXAMPLES
None. APPLICATION USAGE
Applications using this function may be subject to priority inversion, as discussed in the Base Definitions volume of IEEE Std 1003.1-2001, Section 3.285, Priority Inversion. The pthread_barrier_wait() function is part of the Barriers option and need not be provided on all implementations. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
pthread_barrier_destroy() , the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE
/The Open Group 2003 PTHREAD_BARRIER_WAIT(P)
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PTHREAD_BARRIER_DESTROY(P) POSIX Programmer's Manual PTHREAD_BARRIER_DESTROY(P) NAME
pthread_barrier_destroy, pthread_barrier_init - destroy and initialize a barrier object (ADVANCED REALTIME THREADS) 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 pass- ing 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. 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_destroy() function may fail if: EBUSY The implementation has detected an attempt to destroy a barrier while it is in use (for example, while being used in a pthread_bar- rier_wait() call) by another thread. EINVAL The value specified by barrier is invalid. 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. The pthread_barrier_init() function may fail if: EBUSY The implementation has detected an attempt to reinitialize a barrier while it is in use (for example, while being used in a pthread_barrier_wait() call) by another thread. EINVAL The value specified by attr is invalid. These functions shall not return an error code of [EINTR]. The following sections are informative. EXAMPLES
None. APPLICATION USAGE
The pthread_barrier_destroy() and pthread_barrier_init() functions are part of the Barriers option and need not be provided on all imple- mentations. RATIONALE
None. FUTURE DIRECTIONS
None. SEE ALSO
pthread_barrier_wait() , the Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h> COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol- ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE
/The Open Group 2003 PTHREAD_BARRIER_DESTROY(P)