Re: [PATCH] rmap 24 pte_young first

[Hugh Dickins]

rmap 25 of course

On Sat, 8 May 2004, Christoph Hellwig wrote:
> On Sat, May 08, 2004 at 10:56:26PM +0100, Hugh Dickins wrote:
> >  
> > -	if (ptep_test_and_clear_young(pte))
> > +	if (pte_young(*pte) && ptep_test_and_clear_young(pte))
> 
> stupid question - shouldn't the pte_young check simply move to
> the beginning of ptep_test_and_clear_young?

I don't think that would be a good idea.  We're used to those
test_and_clear operations being atomic, putting an initial non-atomic
test inside would make it fundamentally non-atomic.  We know here that
it's not the end of the world if we miss a racing transition of the
young bit, but it wouldn't be good to hide and force that on others.

Hugh

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