On 05/26/2011 02:45 PM, Eric Dumazet wrote:
>>
>> "+m" (*ptr) please...
>>
>> -hpa
>
> Oh well, I guess I was fooled by :
>
> (arch/x86/include/asm/cmpxchg_32.h)
>
> static inline void set_64bit(volatile u64 *ptr, u64 value)
> {
> u32 low = value;
> u32 high = value >> 32;
> u64 prev = *ptr;
>
> asm volatile("\n1:\t"
> LOCK_PREFIX "cmpxchg8b %0\n\t"
> "jnz 1b"
> : "=m" (*ptr), "+A" (prev)
> : "b" (low), "c" (high)
> : "memory");
> }
>
That's =m because the operation implemented by the asm() statement as a
whole is an assignment; the memory location after the entire asm()
statement has executed does not depend on the input value.
-hpa
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