linux-kernel - Re: [PATCH] mmu notifiers #v2

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Message-Id: <1200428333.6755.0.camel@pasglop>
Date:	Wed, 16 Jan 2008 07:18:53 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Andrea Arcangeli <andrea@...ranet.com>
Cc:	Christoph Lameter <clameter@....com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, kvm-devel@...ts.sourceforge.net,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	daniel.blueman@...drics.com, holt@....com, steiner@....com,
	Andrew Morton <akpm@...l.org>, Hugh Dickins <hugh@...itas.com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH] mmu notifiers #v2


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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