linux-kernel - Re: [PATCH 3/3] tty_lock: Localise the lock

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Message-ID: <20120511145243.GE5958@kroah.com>
Date:	Fri, 11 May 2012 07:52:43 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Jiri Slaby <jslaby@...e.cz>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: [PATCH 3/3] tty_lock: Localise the lock

On Fri, May 11, 2012 at 12:40:41PM +0200, Sasha Levin wrote:
> On Tue, May 8, 2012 at 8:12 PM, Sasha Levin <levinsasha928@...il.com> wrote:
> > On Mon, May 7, 2012 at 11:04 PM, Jiri Slaby <jslaby@...e.cz> wrote:
> >> On 05/07/2012 07:00 PM, Sasha Levin wrote:
> >>>> So whatever your trace is showing, that's not the bug. Something more
> >>>> complicated would appear to be afoot.
> >>>
> >>> Oddly enough, tty != tty->link, but the lockdep warning triggers.
> >>>
> >>> Any idea why it might happen?
> >>
> >> I think so, both locks are the same lockdep class. So lockdep thinks it
> >> is the same lock. However this is a false positive. I guess we need
> >> mutex_lock_nested...
> >
> > It looks like it causes an actual deadlock, and hung_tasks screams if
> > left alone for a bit, so it doesn't look like a lockdep issue.
> 
> I've applied the patch that unlocks before hangup, and started seeing
> this new warning instead (sorry if output below looks a bit broken,
> linux-next has a printk rework in progress):

The printk rework should now be working again in linux-next.  Is it
still causing problems for you?

thanks,

greg k-h
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