Subject: Re: [PATCH] mmu notifiers #v2
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reply-To: benh@kernel.crashing.org
To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Christoph Lameter <clameter@sgi.com>, linux-kernel@vger.kernel.org,
       linux-mm@kvack.org, kvm-devel@lists.sourceforge.net,
       Avi Kivity <avi@qumranet.com>, Izik Eidus <izike@qumranet.com>,
       daniel.blueman@quadrics.com, holt@sgi.com, steiner@sgi.com,
       Andrew Morton <akpm@osdl.org>, Hugh Dickins <hugh@veritas.com>,
       Nick Piggin <npiggin@suse.de>
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Date: Wed, 16 Jan 2008 07:18:53 +1100
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On Tue, 2008-01-15 at 13:44 +0100, Andrea Arcangeli wrote:
> On Mon, Jan 14, 2008 at 12:02:42PM -0800, Christoph Lameter wrote:
> > Hmmm... In most of the callsites we hold a writelock on mmap_sem right?
> 
> Not in all, like Marcelo pointed out in kvm-devel, so the lowlevel
> locking can't relay on the VM locks.
> 
> About your request to schedule in the mmu notifier methods this is not
> feasible right now, the notifier is often called with the pte
> spinlocks held. I wonder if you can simply post/queue an event like a
> softirq/pdflush.

Do you have cases where it's -not- called with the PTE lock held ?
 
Ben.


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