From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Lameter <clameter@sgi.com>
Subject: [ofa-general] Re: EMM: disable other notifiers before register and
	unregister
Date: Thu, 3 Apr 2008 12:20:41 -0700 (PDT)
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To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Nick Piggin <npiggin@suse.de>, steiner@sgi.com, Peter Zijlstra <a.p.zijlstra@chello.nl>, linux-mm@kvack.org, Izik Eidus <izike@qumranet.com>, Kanoj Sarcar <kanojsarcar@yahoo.com>, Roland Dreier <rdreier@cisco.com>, linux-kernel@vger.kernel.org, Avi Kivity <avi@qumranet.com>, kvm-devel@lists.sourceforge.net, daniel.blueman@quadrics.com, Robin Holt <holt@sgi.com>, general@lists.openfabrics.org, Hugh Dickins <hugh@veritas.com>
List-Id: linux-mm.kvack.org

On Thu, 3 Apr 2008, Andrea Arcangeli wrote:

> My attempt to fix this once and for all is to walk all vmas of the
> "mm" inside mmu_notifier_register and take all anon_vma locks and
> i_mmap_locks in virtual address order in a row. It's ok to take those
> inside the mmap_sem. Supposedly if anybody will ever take a double
> lock it'll do in order too. Then I can dump all the other locking and

What about concurrent mmu_notifier registrations from two mm_structs 
that have shared mappings? Isnt there a potential deadlock situation?

> faults). So it should be ok to take all those locks inside the
> mmap_sem and implement a lock_vm(mm) unlock_vm(mm). I'll think more
> about this hammer approach while I try to implement it...

Well good luck. Hopefully we will get to something that works.