From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [Bug 9483] circular locking dependency detected
Date: Tue, 4 Dec 2007 13:35:15 -0800
Message-ID: <20071204133515.83b26277.akpm@linux-foundation.org>
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To: Ingo Molnar <mingo@elte.hu>
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On Tue, 4 Dec 2007 22:25:18 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> 
> * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> wrote:
> 
> > =======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 2.6.24-rc3 #6
> > -------------------------------------------------------
> > bash/2294 is trying to acquire lock:
> > (&journal->j_list_lock){--..}, at: [<c01eee2f>] journal_try_to_free_buffers+0x76/0x10c
> > 
> > but task is already holding lock:
> > (inode_lock){--..}, at: [<c01864b6>] drop_pagecache+0x48/0xd8
> > 
> > which lock already depends on the new lock.
> 
> Andrew, drop_pagecache() is root-only and it has some known deadlock, 
> right?
> 

yup.   It takes inode_lock at too high a level so it can walk the per-sb inode
lists.