linux-kernel - Re: [patch 1/3] mmu

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Message-ID: <20080201024742.GD26420@sgi.com>
Date:	Thu, 31 Jan 2008 20:47:42 -0600
From:	Robin Holt <holt@....com>
To:	Christoph Lameter <clameter@....com>
Cc:	Robin Holt <holt@....com>, Andrea Arcangeli <andrea@...ranet.com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: [patch 1/3] mmu_notifier: Core code

On Thu, Jan 31, 2008 at 06:39:19PM -0800, Christoph Lameter wrote:
> On Thu, 31 Jan 2008, Robin Holt wrote:
> 
> > Jack has repeatedly pointed out needing an unregister outside the
> > mmap_sem.  I still don't see the benefit to not having the lock in the mm.
> 
> I never understood why this would be needed. ->release removes the 
> mmu_notifier right now.

Both xpmem and GRU have means of removing their context seperate from
process termination.  XPMEMs is by closing the fd, I believe GRU is
the same.  In the case of XPMEM, we are able to acquire the mmap_sem.
For GRU, I don't think it is possible, but I do not remember the exact
reason.

Thanks,
Robin
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