Subject: Re: 4.3 serial driver crashes with console shortly after boot
To: Andi Kleen <andi@firstfloor.org>,
        Peter Hurley <peter@hurleysoftware.com>
Cc: gregkh@linuxfoundation.org, linux-serial@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20151110002939.GG3533@two.firstfloor.org>
 <56414DE9.20707@hurleysoftware.com>
 <20151110223957.GI3533@two.firstfloor.org>
 <20151110224340.GA30452@two.firstfloor.org>
 <56427AAC.3000409@hurleysoftware.com> <56432316.3040602@hurleysoftware.com>
 <20151111165035.GL3533@two.firstfloor.org>
From: Jiri Slaby <jslaby@suse.cz>
Message-ID: <6f76451d-00e1-a3c5-28f8-ecd3808b8ed2@suse.cz>
Date: Fri, 23 Jun 2017 13:23:48 +0200
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On 11/11/2015, 05:50 PM, Andi Kleen wrote:
> On Wed, Nov 11, 2015 at 06:14:30AM -0500, Peter Hurley wrote:
>> On 11/10/2015 06:15 PM, Peter Hurley wrote:
>>> On 11/10/2015 05:43 PM, Andi Kleen wrote:
>>>> On Tue, Nov 10, 2015 at 11:39:57PM +0100, Andi Kleen wrote:
>>>>>> I've just tried to reproduce this without success on my current
>>>>>> tree which has some additional patches I just posted this am. They weren't
>>>>>> intended to fix crashes but they directly impact the area of concern. Could
>>>>>> you try these three?
>>>>>>
>>>>>> [PATCH v2 2/4] n_tty: Ignore all read data when closing
>>>>>> [PATCH v2 3/4] tty: Abstract and encapsulate tty->closing behavior
>>>>>> [PATCH v2 4/4] tty: Remove drivers' extra tty_ldisc_flush()
>>>>>>
>>>>> Applying the three patches fixes the crash. 
>>>>> I haven't tried to figure out which one did the trick.
>>>>
>>>> Actually I was wrong sorry. It still crashes, but now it doesn't
>>>> hang the system anymore.
>>>
>>> Argghh.
>>> Can you run the patch below and send me full dmesg (privately if you prefer)?
>>
>> Nevermind. I see how it's happening now; it's being initiated by hangup,
>> not close. FWIW, it's been like that nearly forever; your user-space/tool is
>> triggering this because ECHO is on.
> 
> It's just agetty i believe, but there may be some funkiness going on
> with the terminal server or the cable.
> 
> Thanks. I'll just add a NULL pointer check for now, until you have
> a real patch.

It looks like 4.4 (-stable) still suffers from this. Has this ever been
fixed somehow?

thanks,
-- 
js
suse labs