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SubjectRe: spin_lock forgets to clobber memory and other smp fixes [was Re: [patch] waitqueue optimization, 2.4.0-test7]


On Thu, 7 Sep 2000, Andrea Arcangeli wrote:

> On Mon, 4 Sep 2000, Andrea Arcangeli wrote:
>
> >barrier()). I also noticed __sti()/__save_flags() doesn't need to clobber
> >"memory".
>
> I'm not sure anymore if __sti and spin_unlock() doesn't need to clobber
> memory (it looks necessary to make sure the compiler doesn't delay to
> write data to the memory out of the critical section).

"volatile" should be equivalent to clobbering memory, although the gcc
manual pages are certainly not very verbose on the issue.

Adding a memory clobber certainly migth be a good idea. David, who knows
what gcc actually does wrt "volatile"?

Linus

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