61 lines
2.0 KiB
C
61 lines
2.0 KiB
C
/*
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* This file is distributed as part of the MariaDB Corporation MaxScale. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program 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 FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright MariaDB Corporation Ab 2013-2014
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*/
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/**
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* @file atomic.c - Implementation of atomic opertions for the gateway
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 10/06/13 Mark Riddoch Initial implementation
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*
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* @endverbatim
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*/
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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
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atomic_add(int *variable, int value)
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{
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#ifdef __GNUC__
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return (int) __sync_fetch_and_add (variable, value);
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#else
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asm volatile(
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"lock; xaddl %%eax, %2;"
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:"=a" (value)
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: "a" (value), "m" (*variable)
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: "memory" );
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return value;
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#endif
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}
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