linux-kernel - Re: [PATCH 1/3] revoke: misc fixes

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Message-ID: <45FE2189.80709@yahoo.com.au>
Date:	Mon, 19 Mar 2007 16:37:13 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] revoke: misc fixes

Pekka Enberg wrote:
> On 3/16/07, Nick Piggin <nickpiggin@...oo.com.au> wrote:
> 
>> Also, a down_write_trylock attempt inside i_mmap_lock should be a valid
>> optimisation.
> 
> 
> I am not sure what you're thinking here. down_write_trylock acquires
> ->mmap_sem which can deadlock with ->i_mmap_lock, no?

You need hold and wait for a deadlock. So long as you don't block
(on mmap_sem) while holding i_mmap_lock, then you won't deadlock.

So you could just attempt a trylock, and if it works, then you
could revoke the vma right then and there. OTOH, the patch you
subsequently posted looks fine, so unless this is performance
critical then I wouldn't bother ;)

-- 
SUSE Labs, Novell Inc.
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