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From: Dmitry Vyukov <dvyukov@google.com>
Date: Fri, 5 Feb 2016 22:22:10 +0100
Message-ID: <CACT4Y+ZFwt1L+T8OYG-dK6xuQvW1Z7PwrnR95HzcPftADCyKbg@mail.gmail.com>
Subject: Re: tty: deadlock between n_tracerouter_receivebuf and flush_to_ldisc
To: Peter Hurley <peter@hurleysoftware.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Jiri Slaby <jslaby@suse.com>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        J Freyensee <james_p_freyensee@linux.intel.com>,
        syzkaller <syzkaller@googlegroups.com>,
        Kostya Serebryany <kcc@google.com>,
        Alexander Potapenko <glider@google.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        Eric Dumazet <edumazet@google.com>
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On Thu, Feb 4, 2016 at 7:48 PM, Dmitry Vyukov <dvyukov@google.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.
>
> Working hard on it now.

No luck so far. I will leave it running, but I will be OOO whole next week.