linux-kernel - Re: [cgroup or VFS ?] INFO: possible recursive locking detected

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Date:	Tue, 10 Feb 2009 09:32:35 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [cgroup or VFS ?] INFO: possible recursive locking detected

On Tue, 2009-02-10 at 11:06 +0800, Li Zefan wrote:
> > It seems to me we can simply put the new s_umount instance in a
> > different subclass. Its a bit unusual to use _nested for the outer lock,
> > but lockdep doesn't particularly cares about subclass order.
> > 
> > If there's any issue with the callers of sget() assuming the s_umount
> > lock being of sublcass 0, then there is another annotation we can use to
> > fix that, but lets not bother with that if this is sufficient.
> > 
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> 
> Tested-by: Li Zefan <lizf@...fujitsu.com>
> 
> Thanks!
> 
> a minor comment
> 
> > +		 * lock of the old one. Since these are clearly distrinct
> 
> s/distrinct/distinct

Yes, someone else was kind enough to point that out as well :-)

Al, do you want a resend or will you fix that up when you add the patch
to your queue?

> BTW, I found another bug in current code:

Yep, looks good, freeing held locks makes lockdep unhappy.

> From: Li Zefan <lizf@...fujitsu.com>
> Date: Tue, 10 Feb 2009 10:55:53 +0800
> Subject: [PATCH] vfs: add missing unlock in sget()
> 
> We should release s->s_umount before calling destroy_super(s).
> 
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> ---

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