Re: resend Re: [PATCH] final merging patch -- significant mozilla speedup.

[Andrea Arcangeli <andrea@suse.de>]

On Sun, Aug 19, 2001 at 02:55:32AM +0200, Andrea Arcangeli wrote:
> On Sat, Aug 18, 2001 at 09:50:04PM -0300, Rik van Riel wrote:
> > On Sun, 19 Aug 2001, Andrea Arcangeli wrote:
> > > On Sat, Aug 18, 2001 at 08:10:50PM -0400, Ben LaHaise wrote:
> > 
> > > > Your patch performs a few odd things like:
> > > >
> > > > +       vma->vm_raend = 0;
> > ...
> > > > which I would argue are incorrect.  Remember that page faults rely on
> > >
> > > vm_raend is obviously correct.
> > 
> > Why ?
> 
> Do you know of any piece of code that touches vm_raend without the the
> mmap_sem acquired? If yes you will change my mind about it otherwise you
> will know why.

btw, while my change to madvise is obviously correct (madvise holds the
write sem), I noticed now that the other code changing vm_raend is racy
(but this is totally unrelated to my changes): the nopage callback
during the page fault updates the vm_raend with only the read semaphore
acquired so multiple threads could get confused, however it seems a
controlled race that cannot harm.

Andrea
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