Re: [RFC] should VM_BUG_ON(cond) really evaluate cond

From: Linus Torvalds
Date: Thu Oct 27 2011 - 21:35:19 EST

On Thu, Oct 27, 2011 at 6:25 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> Seems reasonable too. In fact we usually should have memory barriers
> for this anyways which obsolete the volatile.

No we shouldn't. Memory barriers are insanely expensive, and pointless
for atomics - that aren't ordered anyway.

You may mean compiler barriers.

That said, removing the volatile entirely might be a good idea, and
never mind any barriers at all. The ordering for atomics really isn't
well enough specified that we should care. So I wouldn't object to a
patch that just removes the volatile entirely, but it would have to be
accompanied with quite a bit of testing, in case some odd case ends up
depending on it. But nothing *should* be looping on those things

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