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Date: Mon, 4 Dec 2006 00:32:17 -0800
From: Andrew Morton <akpm@osdl.org>
To: Fengguang Wu <fengguang.wu@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org
Subject: Re: drop_pagecache: Possible circular locking dependency
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On Mon, 4 Dec 2006 16:09:02 +0800
Fengguang Wu <fengguang.wu@gmail.com> wrote:

> Got the following message when doing some benchmarks.
> I guess we should not hold inode_lock on calling invalidate_inode_pages().
> Any ideas?
> 
> Fengguang Wu
> 
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.19-rc6-mm2 #3
> -------------------------------------------------------
> rabench.sh/7467 is trying to acquire lock:
>  (&journal->j_list_lock){--..}, at: [<ffffffff8113bdbc>] journal_try_to_free_buffers+0xdc/0x1c0
> 
> but task is already holding lock:
>  (inode_lock){--..}, at: [<ffffffff810fe857>] drop_pagecache+0x67/0x120
> 
> which lock already depends on the new lock.
> 

drat, I was afraid someone would notice.

It's Hard To Fix.  Removing /proc/sys/vm/drop_pagecache would in fact be 
my preferred fix.
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