Date: Thu, 31 Jan 2008 19:01:44 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Robin Holt <holt@sgi.com>
cc: Andrea Arcangeli <andrea@qumranet.com>, Avi Kivity <avi@qumranet.com>,
       Izik Eidus <izike@qumranet.com>, kvm-devel@lists.sourceforge.net,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, steiner@sgi.com,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       daniel.blueman@quadrics.com
Subject: Re: [patch 1/3] mmu_notifier: Core code
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On Thu, 31 Jan 2008, Robin Holt wrote:

> 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.

For any action initiated from user space you will not hold mmap sem. So 
you can call the unregister function. Then you need to do a 
synchronize_rcu before freeing the structures.

It is also possible to shut this down outside via f.e. a control thread. 
The control thread can acquire mmap_sem and then unregister the notifier.

Am I missing something?

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