genode/base/include/arm/cpu/atomic.h
2013-01-10 21:44:47 +01:00

55 lines
1.4 KiB
C++

/*
* \brief Atomic operations for ARM
* \author Norman Feske
* \author Stefan Kalkowski
* \date 2007-04-28
*/
/*
* Copyright (C) 2007-2013 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__ARM__CPU__ATOMIC_H_
#define _INCLUDE__ARM__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.
*
* \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)
{
unsigned long equal, not_exclusive;
__asm__ __volatile__(
"@ cmpxchg\n"
" 1: \n"
" ldrex %0, [%2] \n"
" cmp %0, %3 \n"
" bne 2f \n"
" strexeq %0, %4, [%2]\n"
" teqeq %0, #0 \n"
" bne 1b \n"
" moveq %1, #1 \n"
" 2: \n"
" movne %1, #0 \n"
: "=&r" (not_exclusive), "=&r" (equal)
: "r" (dest), "r" (cmp_val), "r" (new_val)
: "cc");
return equal && !not_exclusive;
}
}
#endif /* _INCLUDE__ARM__CPU__ATOMIC_H_ */