linux-kernel - Re: [RFC][PATCH] splice: fix deadlock

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Date:	Sun, 18 Jan 2009 19:20:43 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Vegard Nossum <vegard.nossum@...il.com>
Cc:	Jens Axboe <axboe@...e.de>, Eric Dumazet <dada1@...mosbay.com>,
	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] splice: fix deadlock

On Sun, Jan 18 2009, Vegard Nossum wrote:
> From 8e1d58b03b47d937bc5e53d902bac6e690709034 Mon Sep 17 00:00:00 2001
> From: Vegard Nossum <vegard.nossum@...il.com>
> Date: Sun, 18 Jan 2009 16:07:29 +0100
> Subject: [PATCH] splice: fix deadlock
> 
> splice from a file or socket needs to lock both the file/socket and the
> pipe inodes. pipe_wait() unlocks only the pipe lock, regardless of the
> order in which they were taken.
> 
> This patch adds an additional (optional) argument to pipe_wait(); if
> specified, pipe_wait() will unlock and reacquire both inode locks.
> 
> It fixes the lockup that occurs with the test-case below, but please
> review carefully. Consider this patch a proposal rather than a fix.

Thanks for the bug report and test case, it is indeed buggy! Good
spotting. I'll review your patch thoroughly and test it, and then
integrate your patch.

-- 
Jens Axboe

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