linux-kernel - Re: mq: INFO: possible circular locking dependency detected

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Date:	Tue, 7 Aug 2012 13:04:12 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	viro@...iv.linux.org.uk,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	Kamal Mostafa <kamal@...onical.com>,
	"Peter M. Petrakis" <peter.petrakis@...onical.com>,
	Dann Frazier <dann.frazier@...onical.com>,
	Massimo Morana <massimo.morana@...onical.com>,
	Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org
Subject: Re: mq: INFO: possible circular locking dependency detected

On Mon, Aug 06, 2012 at 01:08:56AM +0800, Fengguang Wu wrote:
> On Sat, Aug 04, 2012 at 12:59:31PM +0200, Sasha Levin wrote:
> > Hi all,
> >
> > While fuzzing with trinity inside a KVM tools guest, using latest -next kernel, I've stumbled on the dump below.
> >
> > I think this is the result of commit 765927b2 ("switch dentry_open() to struct path, make it grab references itself").
> >
> > [   62.090519] ======================================================
> > [   62.091016] [ INFO: possible circular locking dependency detected ]
> > [   62.091016] 3.6.0-rc1-next-20120803-sasha #544 Tainted: G        W
> > [   62.091016] -------------------------------------------------------
> > [   62.091016] trinity-child0/6077 is trying to acquire lock:
> > [   62.091016]  (&sb->s_type->i_mutex_key#14){+.+.+.}, at: [<ffffffff8127c074>] vfs_unlink+0x54/0x100
> > [   62.091016]
> > [   62.091016] but task is already holding lock:
> > sb_writers#8){.+.+.+}, at: [<ffffffff812900bf>] mnt_want_write+0x1f/0x50
>
> I met the same problem and it's bisected down to:
>
> commit eb04c28288bb0098d0e75d81ba2a575239de71d8
> Author: Jan Kara <jack@...e.cz>
> Date:   Tue Jun 12 16:20:35 2012 +0200
>
>     fs: Add freezing handling to mnt_want_write() / mnt_drop_write()

FYI, here is a different back trace on that commit.

[    3.255043] ======================================================
[    3.255052] [ INFO: possible circular locking dependency detected ]
[    3.255052] 3.5.0-rc6-bisect-00355-geb04c28 #4 Not tainted         
[    3.255052] -------------------------------------------------------
[    3.255052] init/1 is trying to acquire lock:
[    3.255052]  (&mm->mmap_sem){++++++}, at: [<ffffffff81180d00>] might_fault+0x70/0xe0
[    3.255052]
[    3.255052] but task is already holding lock:
[    3.255052]  (&sb->s_type->i_mutex_key){+.+.+.}, at: [<ffffffff811d191e>] vfs_readdir+0x6e/0x130

Thanks,
Fengguang

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