79 строки
2.1 KiB
Plaintext
79 строки
2.1 KiB
Plaintext
.\" -*- nroff -*-
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.\" Copyright (c) 2015 University of Houston. All rights reserved.
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.\" Copyright (c) 2015 Mellanox Technologies, Inc.
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.\" $COPYRIGHT$
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.de Vb
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.ft CW
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.nf
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..
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.de Ve
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.ft R
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.fi
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..
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.TH "SHMEM\\_LOCK" "3" "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fIshmem_set_lock\fP(3),
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\fIshmem_clear_lock\fP(3),
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\fIshmem_test_lock\fP(3)
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\- Releases, locks, and tests a mutual exclusion memory lock.
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.SH SYNOPSIS
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C or C++:
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.Vb
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#include <mpp/shmem.h>
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void shmem_clear_lock(volatile long *lock);
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void shmem_set_lock(volatile long *lock);
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int shmem_test_lock(volatile long *lock);
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.Ve
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Fortran:
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.Vb
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INCLUDE "mpp/shmem.fh"
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INTEGER lock, SHMEM_TEST_LOCK
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CALL SHMEM_CLEAR_LOCK(lock)
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CALL SHMEM_SET_LOCK(lock)
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I = SHMEM_TEST_LOCK(lock)
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.Ve
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.SH DESCRIPTION
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The shmem_set_lock routine sets a mutual exclusion lock after waiting for the lock to be
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freed by any other PE currently holding the lock. Waiting PEs are assured of getting the lock
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in a first\-come, first\-served manner.
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.PP
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The shmem_clear_lock routine releases a lock previously set by shmem_set_lock after
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ensuring that all local and remote stores initiated in the critical region are complete.
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.PP
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The shmem_test_lock function sets a mutual exclusion lock only if it is currently cleared.
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By using this function, a PE can avoid blocking on a set lock. If the lock is currently set, the
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function returns without waiting.
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These routines are appropriate for protecting a critical region from simultaneous update by
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multiple PEs.
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They accept the following arguments:
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.TP
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lock
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A symmetric data object that is a scalar variable or an array of length 1. This
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data object must be set to 0 on all processing elements (PEs) prior to the first use. lock must
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be of type integer. If you are using Fortran, it must be of default kind.
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.PP
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.SH NOTES
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The term symmetric data object is defined on \fIintro_shmem\fP(3)\&.
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.PP
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.SH RETURN VALUES
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The shmem_test_lock function returns 0 if the lock was originally cleared and this call
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was able to set the lock. A value of 1 is returned if the lock had been set and the call returned
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without waiting to set the lock.
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.PP
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.SH SEE ALSO
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\fIintro_shmem\fP(3)
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