Messages in this thread | | | Date | Fri, 21 May 2010 16:06:00 +1000 | From | Nick Piggin <> | Subject | Re: [PATCH 2/2]: atomic_t: Remove volatile from atomic_t definition |
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On Thu, May 20, 2010 at 10:54:54PM -0700, David Miller wrote: > From: Nick Piggin <npiggin@suse.de> > Date: Fri, 21 May 2010 15:27:46 +1000 > > > Hmm, I'm missing something. David, back up a second, as far as I can see, > > with Anton's patches, atomic_read() *is* effectively just ACCESS_ONCE() > > now. Linus pointed out that header tangle is the reason not to just use > > the macro. > > My bad, I was under the impression that the proposal was to remove > volatile usage and also not even do ACCESS_ONCE() in atomic_read(). > > And then explicitly annotate call sits that actually need the > ACCESS_ONCE() semantic.
Ah ok, no. I see ACCESS_ONCE is a fundamental ("obvious") property of atomic_read, so we definitely should keep it, even if we could audit everyone.
Actually, I bet we have a lot of bugs there with loading integers and pointers atomically, where the code assumes the loaded value will not be reloaded by the compiler, because it is an easy thing to assume.
atomic_read_light could be useful though, for sure.
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