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.TH "SHMEM_CLEAR_LOCK" "3" "Apr 11, 2024" "" "Open MPI"
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\fI\%shmem_set_lock\fP(3), \fI\%shmem_clear_lock\fP(3), \fI\%shmem_test_lock\fP(3) \-
Releases, locks, and tests a mutual exclusion memory lock.
.SH SYNOPSIS
.sp
C or C++:
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.EX
#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)
.EE
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Fortran:
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.EX
INCLUDE \(dqmpp/shmem.fh\(dq

INTEGER lock, SHMEM_TEST_LOCK

CALL SHMEM_CLEAR_LOCK(lock)

CALL SHMEM_SET_LOCK(lock)

I = SHMEM_TEST_LOCK(lock)
.EE
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.SH DESCRIPTION
.sp
The \fI\%shmem_set_lock\fP 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.
.sp
The \fI\%shmem_clear_lock\fP routine releases a lock previously set by
\fI\%shmem_set_lock\fP after ensuring that all local and remote stores initiated
in the critical region are complete.
.sp
The \fI\%shmem_test_lock\fP 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:
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.TP
.B 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.
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.SH NOTES
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The term symmetric data object is defined on \fIintro_shmem\fP(3).
.SH RETURN VALUES
.sp
The \fI\%shmem_test_lock\fP 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.
.sp
\fBSEE ALSO:\fP
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\fIintro_shmem\fP(3)
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.SH COPYRIGHT
2003-2024, The Open MPI Community
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