2011-12-22 15:19:25 +00:00
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/*
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* \brief Atomic operations for x86
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* \author Norman Feske
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* \date 2006-07-26
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*
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* Based on l4util/include/ARCH-x86/atomic_arch.h.
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*/
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/*
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2012-01-03 14:35:05 +00:00
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* Copyright (C) 2006-2012 Genode Labs GmbH
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2011-12-22 15:19:25 +00:00
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__X86__CPU__ATOMIC_H_
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#define _INCLUDE__X86__CPU__ATOMIC_H_
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namespace Genode {
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/**
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* Atomic compare and exchange
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*
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* This function compares the value at dest with cmp_val.
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* If both values are equal, dest is set to new_val. If
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* both values are different, the value at dest remains
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* unchanged.
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*
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* \return 1 if the value was successfully changed to new_val,
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* 0 if cmp_val and the value at dest differ.
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*/
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inline int cmpxchg(volatile int *dest, int cmp_val, int new_val)
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{
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int tmp;
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__asm__ __volatile__
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(
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"lock cmpxchgl %1, %3 \n\t"
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:
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"=a" (tmp) /* 0 EAX, return val */
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:
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"r" (new_val), /* 1 reg, new value */
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"0" (cmp_val), /* 2 EAX, compare value */
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"m" (*dest) /* 3 mem, destination operand */
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:
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"memory", "cc"
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);
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return tmp == cmp_val;
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}
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}
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#endif /* _INCLUDE__X86__CPU__ATOMIC_H_ */
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