SHMEM_LOCK(3) Open MPI SHMEM_LOCK(3)
NAME
shmem_set_lock(3), shmem_clear_lock(3), shmem_test_lock(3) - Releases,
locks, and tests a mutual exclusion memory lock.
SYNOPSIS
C or C++:
#include <mpp/shmem.h>
void shmem_clear_lock(volatile long *lock);
void shmem_set_lock(volatile long *lock);
int shmem_test_lock(volatile long *lock);
Fortran:
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 initi-
ated 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 re-
gion from simultaneous update by multiple PEs. They accept the follow-
ing 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 in-
teger. If you are using Fortran, it must be of default kind.
NOTES
The term symmetric data object is defined on intro_shmem(3).
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 re-
turned if the lock had been set and the call returned without waiting
to set the lock.
SEE ALSO
intro_shmem(3)
4.1.2 Nov 24, 2021 SHMEM_LOCK(3)
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