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@tux21b
Created October 20, 2012 17:13
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// The "atomic.h" file provides low-level atomic memory primitives for the
// x86 plattform. All functions in this file provide sequential memory
// consistency.
// atomic_load atomically loads *addr.
static inline int atomic_load(int *addr)
{
int val = *(volatile const int*)(addr);
__asm__ __volatile__ ("" ::: "memory");
return val;
}
// atomic_store atomically stores val into *addr.
static inline void atomic_store(int *addr, int val)
{
__asm__ __volatile__ (
"xchgl %0, %1\n" :
"=q" (val) :
"m" (*addr), "0" (val) :
"memory");
}
// atomic_add atomically adds delta to *addr and returns the new value.
static inline int atomic_add(int *addr, int delta)
{
int t = delta;
__asm__ __volatile__ (
"lock; xaddl %0, %1" :
"+q" (delta), "+m" (*addr) :
:
"memory");
return delta + t;
}
// atomic_cas executes the compare-and-swap operation on *addr.
static inline int atomic_cas(int *addr, int expected, int desired)
{
__asm__ __volatile__ ("" ::: "memory");
int prev = expected;
__asm__ __volatile__ (
"lock; cmpxchgl %1, %2\n" :
"=a" (prev) :
"q" (desired), "m" (*addr), "a" (expected) :
"memory");
int success = (prev == expected);
__asm__ __volatile__ ("" ::: "memory");
return success;
}
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