Messages in this thread | | | Date | Mon, 25 May 2009 20:34:14 +0100 | From | Russell King - ARM Linux <> | Subject | Re: Broken ARM atomic ops wrt memory barriers (was : [PATCH] Add cmpxchg support for ARMv6+ systems) |
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On Mon, May 25, 2009 at 01:29:55PM -0400, Mathieu Desnoyers wrote: > Basically, to make sure we don't forget anything, someone should go > through all the atomic_ops.txt document once more and audit all ARM > primitives.
That's easy to say - it took me more than half an hour of reading through atomic_ops.txt to work out what was required for things like cmpxchg, xchg, etc because it's _very_ waffley and verbose, and directs you to other parts of the document.
For example, for atomic_cmpxchg it directs you to 'cas' but cas doesn't really say what the barrier requirements are - reading it leaves me to expect that provided spinlocks are serializing themselves, it's fine if 'cas' itself isn't.
Maybe if someone has a few days to translate atomic_ops.txt into a succinct set of requirements, and get _that_ reviewed, then we could properly audit this stuff.
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