linux-kernel - Re: [patch] inotify: fix deadlock found by lockdep

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Message-Id: <1153778917.2808.14.camel@betsy.boston.ximian.com>
Date:	Mon, 24 Jul 2006 18:08:37 -0400
From:	Robert Love <rml@...ell.com>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Reuben Farrelly <reuben-lkml@...b.net>,
	Ingo Molnar <mingo@...e.hu>,
	John McCutchan <john@...nmccutchan.com>,
	Andrew Morton <akpm@...l.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>, rml@...ian.com,
	viro@...iv.linux.org.uk
Subject: Re: [patch] inotify: fix deadlock found by lockdep

On Mon, 2006-07-24 at 19:21 +0200, Arjan van de Ven wrote:

> inotify_dev_queue_event schedules a kernel_event which does a
> kmem_cache_alloc( , GFP_KERNEL) which may try to shrink slabs, including
> the inode cache .. which then takes iprune_mutex. 
> 
> And voila, there is an AB, a BC, a CD relationship (even a direct BCD),
> and also now a DA relationship -> a circular type AB-BA deadlock but
> involving 4 locks.
> 
> The solution is simple: kernel_event() is NOT allowed to use GFP_KERNEL,
> but must use GFP_NOFS to not cause recursion into the VFS.
> 
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>

Nice catch.

Signed-off-by: Robert Love <rml@...ell.com>

	Robert Love


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