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SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
Christoph Lameter wrote:
> On Fri, 17 Aug 2007, Paul E. McKenney wrote:
>
>> On Sat, Aug 18, 2007 at 08:09:13AM +0800, Herbert Xu wrote:
>>> On Fri, Aug 17, 2007 at 04:59:12PM -0700, Paul E. McKenney wrote:
>>>> gcc bugzilla bug #33102, for whatever that ends up being worth. ;-)
>>> I had totally forgotten that I'd already filed that bug more
>>> than six years ago until they just closed yours as a duplicate
>>> of mine :)
>>>
>>> Good luck in getting it fixed!
>> Well, just got done re-opening it for the third time. And a local
>> gcc community member advised me not to give up too easily. But I
>> must admit that I am impressed with the speed that it was identified
>> as duplicate.
>>
>> Should be entertaining! ;-)
>
> Right. ROTFL... volatile actually breaks atomic_t instead of making it
> safe. x++ becomes a register load, increment and a register store. Without
> volatile we can increment the memory directly. It seems that volatile
> requires that the variable is loaded into a register first and then
> operated upon. Understandable when you think about volatile being used to
> access memory mapped I/O registers where a RMW operation could be
> problematic.

So, if we want consistent behavior, we're pretty much screwed unless we use
inline assembler everywhere?

-- Chris
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