linux-kernel - Re: tty: deadlock between n_tracerouter_receivebuf and flush_to

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Message-ID: <56B39C7A.2080606@hurleysoftware.com>
Date:	Thu, 4 Feb 2016 10:46:18 -0800
From:	Peter Hurley <peter@...leysoftware.com>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Jiri Slaby <jslaby@...e.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	J Freyensee <james_p_freyensee@...ux.intel.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: tty: deadlock between n_tracerouter_receivebuf and flush_to_ldisc

On 02/04/2016 05:17 AM, Dmitry Vyukov wrote:
> On Thu, Feb 4, 2016 at 1:39 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>> On Wed, Feb 3, 2016 at 8:09 PM, Peter Hurley <peter@...leysoftware.com> wrote:

>>> Hopefully, once the problem with the bad stacktraces are fixed, the
>>> actual circular lock dependencies will be clear.

> Found a bug in lockdep. Yes, the first stack is correct, and the saved
> stack is just a random, unrelated stack. Will mail a fix.

Ok, so with the lockdep bug fixed, those reports should now have the
correct stack traces.

I'd appreciate if you could re-generate the original report, so I can examine
if my speculative fix was appropriate.

And then if you would re-generate the more recent report, I'll relook at
that.

Regards,
Peter Hurley