62 lines
1.9 KiB
C
62 lines
1.9 KiB
C
#pragma once
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/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2019-07-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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/**
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* @file atomic.h The atomic operations used within the gateway
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*/
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#include <maxscale/cdefs.h>
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MXS_BEGIN_DECLS
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/**
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* Implementation of an atomic add operation for the GCC environment, or the
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* X86 processor. If we are working within GNU C then we can use the GCC
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* atomic add built in function, which is portable across platforms that
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* implement GCC. Otherwise, this function currently supports only X86
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* architecture (without further development).
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*
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* Adds a value to the contents of a location pointed to by the first parameter.
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* The add operation is atomic and the return value is the value stored in the
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* location prior to the operation. The number that is added may be signed,
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* therefore atomic_subtract is merely an atomic add with a negative value.
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*
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* @param variable Pointer the the variable to add to
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* @param value Value to be added
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* @return The value of variable before the add occurred
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*/
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int atomic_add(int *variable, int value);
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/**
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* @brief Impose a full memory barrier
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*
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* A full memory barrier guarantees that all store and load operations complete
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* before the function is called.
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*
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* Currently, only the GNUC __sync_synchronize() is used. C11 introduces
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* standard functions for atomic memory operations and should be taken into use.
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*
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* @see https://www.kernel.org/doc/Documentation/memory-barriers.txt
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*/
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static inline void atomic_synchronize()
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{
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#ifdef __GNUC__
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__sync_synchronize(); /* Memory barrier. */
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#else
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#error "No GNUC atomics available."
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#endif
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}
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MXS_END_DECLS
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