Re: [PATCH v2 7/7] ARM: atomics: define our SMP atomics in terms of _relaxed operations

Waiman Long
2015-07-17T00:00:37Z

On 07/16/2015 05:08 PM, Peter Zijlstra wrote:
> On Thu, Jul 16, 2015 at 04:40:03PM -0400, Waiman Long wrote:
>> On 07/16/2015 11:32 AM, Will Deacon wrote:
>>> @@ -117,6 +115,8 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
>>> #error "SMP is not supported on this platform"
> ^^^^^^^^^^^^^

That #error is only for ARMv5 or below.

>>> #endif
>>>
>>> +#define xchg xchg_relaxed
>> Is that a typo? I think xchg() needs to be a full memory barrier.
> Pointless on UP.