56 lines
1.3 KiB
C++
56 lines
1.3 KiB
C++
/*
|
|
* \brief Atomic operations for x86
|
|
* \author Norman Feske
|
|
* \date 2006-07-26
|
|
*
|
|
* Based on l4util/include/ARCH-x86/atomic_arch.h.
|
|
*/
|
|
|
|
/*
|
|
* Copyright (C) 2006-2013 Genode Labs GmbH
|
|
*
|
|
* This file is part of the Genode OS framework, which is distributed
|
|
* under the terms of the GNU General Public License version 2.
|
|
*/
|
|
|
|
#ifndef _INCLUDE__X86__CPU__ATOMIC_H_
|
|
#define _INCLUDE__X86__CPU__ATOMIC_H_
|
|
|
|
namespace Genode {
|
|
|
|
/**
|
|
* Atomic compare and exchange
|
|
*
|
|
* This function compares the value at dest with cmp_val.
|
|
* If both values are equal, dest is set to new_val. If
|
|
* both values are different, the value at dest remains
|
|
* unchanged.
|
|
*
|
|
* Note, that cmpxchg() represents a memory barrier.
|
|
*
|
|
* \return 1 if the value was successfully changed to new_val,
|
|
* 0 if cmp_val and the value at dest differ.
|
|
*/
|
|
inline int cmpxchg(volatile int *dest, int cmp_val, int new_val)
|
|
{
|
|
int tmp;
|
|
|
|
__asm__ __volatile__
|
|
(
|
|
"lock cmpxchgl %1, %3 \n\t"
|
|
:
|
|
"=a" (tmp) /* 0 EAX, return val */
|
|
:
|
|
"r" (new_val), /* 1 reg, new value */
|
|
"0" (cmp_val), /* 2 EAX, compare value */
|
|
"m" (*dest) /* 3 mem, destination operand */
|
|
:
|
|
"memory", "cc"
|
|
);
|
|
|
|
return tmp == cmp_val;
|
|
}
|
|
}
|
|
|
|
#endif /* _INCLUDE__X86__CPU__ATOMIC_H_ */
|