Re: [patch 2] mm: speculative get_page

[Nick Piggin <nickpiggin@yahoo.com.au>]

David S. Miller wrote:

> From: Nick Piggin <nickpiggin@yahoo.com.au>
> Subject: Re: [patch 2] mm: speculative get_page
> Date: Tue, 28 Jun 2005 14:50:31 +1000
>
>
> > William Lee Irwin III wrote:
> >
> >
> > > On Tue, Jun 28, 2005 at 11:42:16AM +1000, Nick Piggin wrote:
> > >
> > > spin_unlock() does not imply a memory barrier.
> > Intriguing...
>
> BTW, I disagree with this assertion.  spin_unlock() does imply a
> memory barrier.
>
> All memory operations before the release of the lock must execute
> before the lock release memory operation is globally visible.

Yes, it appears that way from looking at a sample set of arch
code too (ie. those without strictly ordered stores put an
explicit barrier there).

I've always understood spin_unlock to imply a barrier.


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