Other Alias
shmem_set_lock3, shmem_clear_lock3SYNOPSIS
C or C++:
#include <mpp/shmem.h>
void shmem_clear_lock(long *lock);
void shmem_set_lock(long *lock);
int shmem_test_lock(long *lock);
INCLUDE "mpp/shmem.fh" INTEGER lock, SHMEM_TEST_LOCK CALL SHMEM_CLEAR_LOCK(lock) CALL SHMEM_SET_LOCK(lock) I = SHMEM_TEST_LOCK(lock)
DESCRIPTION
The shmem_set_lock routine sets a mutual exclusion lock after waiting for the lock to be freed by any other PE currently holding the lock. Waiting PEs are assured of getting the lock in a first-come, first-served manner.
The shmem_clear_lock routine releases a lock previously set by shmem_set_lock after ensuring that all local and remote stores initiated in the critical region are complete.
The shmem_test_lock function sets a mutual exclusion lock only if it is currently cleared. By using this function, a PE can avoid blocking on a set lock. If the lock is currently set, the function returns without waiting. These routines are appropriate for protecting a critical region from simultaneous update by multiple PEs. They accept the following arguments:
- lock
- A symmetric data object that is a scalar variable or an array of length 1. This data object must be set to 0 on all processing elements (PEs) prior to the first use. lock must be of type integer. If you are using Fortran, it must be of default kind.
RETURN VALUES
The shmem_test_lock function returns 0 if the lock was originally cleared and this call was able to set the lock. A value of 1 is returned if the lock had been set and the call returned without waiting to set the lock.