linux-kernel - Re: [PATCH] - Fix unmap_vma() bug related to mmu

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Message-ID: <20100128031841.GG6616@sgi.com>
Date:	Wed, 27 Jan 2010 21:18:42 -0600
From:	Robin Holt <holt@....com>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Robin Holt <holt@....com>, Jack Steiner <steiner@....com>,
	cl@...ux-foundation.org, mingo@...e.hu, tglx@...utronix.de,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] - Fix unmap_vma() bug related to mmu_notifiers

On Tue, Jan 26, 2010 at 10:38:53PM +0100, Andrea Arcangeli wrote:
> On Tue, Jan 26, 2010 at 03:29:04PM -0600, Robin Holt wrote:
> > On Mon, Jan 25, 2010 at 10:16:15PM +0100, Andrea Arcangeli wrote:
> > > The old patches are in my ftp area, they should still apply, you
> > > should concentrate testing with those additional ones applied, then it
> > > will work for xpmem too ;)
> > 
> > Andrea, could you point me at your ftp area?
> 
> Sure, this is the very latest version I maintained:
> 
> http://www.kernel.org/pub/linux/kernel/people/andrea/patches/v2.6/2.6.26-rc7/mmu-notifier-v18/

Let me start with what XPMEM currently has.

We adjusted xpmem so that the mmu_notifier_invalidate_page() callout
does not need to sleep.  It takes the arguments passed in and adds them
to a queue for clearing the pages.  We added a seperate kernel thread
which manages this clearing.

The mmu_notifier_invalidate_range_end() likewise does not really need
to sleep either.

That leaves the mmu_notifier_invalidate_range_start() callout.  This does
not need to drop the mm_sem.  It does need to be able to sleep waiting
for the invalidations to complete on the other process.  That other
process may be on a different SSI connected to the same Numalink fabric.

I think that with the SRCU patch, we have enough.  Is that true or have
I missed something?

Thanks,
Robin
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