48 lines
1.9 KiB
C
48 lines
1.9 KiB
C
/*
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://zfsonlinux.org/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _SPL_COMPILER_COMPAT_H
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#define _SPL_COMPILER_COMPAT_H
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#include <linux/compiler.h>
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#ifndef ACCESS_ONCE
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/*
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* Prevent the compiler from merging or refetching accesses. The compiler
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* is also forbidden from reordering successive instances of ACCESS_ONCE(),
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* but only when the compiler is aware of some particular ordering. One way
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* to make the compiler aware of ordering is to put the two invocations of
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* ACCESS_ONCE() in different C statements.
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*
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* This macro does absolutely -nothing- to prevent the CPU from reordering,
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* merging, or refetching absolutely anything at any time. Its main intended
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* use is to mediate communication between process-level code and irq/NMI
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* handlers, all running on the same CPU.
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*/
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/* Taken from 2.6.33.2 */
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# define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
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#endif
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#endif /* _SPL_COMPILER_COMPAT_H */
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