Kernel panic on stable kernel 3.8.2 when closing bluetooth dun connection

March 20th, 2013 - 05:20 am ET by Sergio Callegari | Report spam
Hi,

This is just a short note to let you know that 3.8.2 panics on closing a
bluetooth dun connection.

This is seen with the ubuntu mainline kernel 3.8.2 that should be a vanilla
stable kernel.

Observed on a DELL E6500 which has BCM2046 Bluetooth while connecting to the
internet using a Samsung Galaxy S mobile phone via bluetooth DUN through the
network manager. When network manager is asked to close the connection, the
kernel panics, the system drops out of Xorg, shows for a couple of seconds a
long log including the words 'panic' and 'not synching', the numlock, caps-lock
keys start flashing and the system freezes.

It is 100% repeatable.

The ubuntu kernel, that is a 3.5.0 plus ubuntu tweaks, backports, etc does not
panic.

Thanks for the attention and best regards,

Sergio Callegari
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#1 Greg KH
March 20th, 2013 - 11:20 am ET | Report spam
On Wed, Mar 20, 2013 at 11:18:38AM +0100, Sergio Callegari wrote:
Hi,

This is just a short note to let you know that 3.8.2 panics on
closing a bluetooth dun connection.



Have you notified the linux bluetooth developers about this? Is this
new in 3.8.2 and 3.8.1 or 3.8 works fine?

thanks,

greg k-h
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#2 Sergio Callegari
March 21st, 2013 - 07:00 am ET | Report spam
On 20/03/2013 17:17, Greg KH wrote:
Have you notified the linux bluetooth developers about this? Is this new in
3.8.2 and 3.8.1 or 3.8 works fine? thanks, greg k-h



Hi, thanks for the advice.

I have verified that the issue was introduced with 3.8.0 and is not due to
stabilization patches in the 3.8.x series. 3.7.x is fine (from x=0 to x=8)
Sorry for not having checked earlier, but I was incorrectly taken for granted
that if the bug was back in 3.8.0 someone would have noticed already...
Now notifying the bluetooth developers too.

Sergio
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#3 Sergio Callegari
March 22nd, 2013 - 05:40 pm ET | Report spam
In the end it may not be caused by bluetooth, but by ppp.

Found bug reports on ubuntu indicating that 3.8.x panic on ppp disconnection.
Unfortunately, I cannot try without bluetooth with my configuration.
(when wired, phone does not use ppp, but appears as a wired network interface).

Sergio
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#4 Sergio Callegari
April 08th, 2013 - 12:20 pm ET | Report spam
Hi,

I'm following up with a previous email where I was reporting a systematic kernel
panic/system freeze when closing a bluetooth DUN connection.

I have made a few more tests, all with 64 bit machines:

- Bug happens with all the 3.8.x kernel series, up to the latest 3.8.6
- Bug happens with the 3.9RC6 kernel
- Bug is not present up to 3.7.x, including the latest 3.7.10
- Bug happens on the DELL E6500 laptop that has a Dell Computer Corp. Wireless
370 Bluetooth Mini-card
- Bug also happens on a desktop that has a Cambridge Silicon Radio, Ltd
Bluetooth Dongle (HCI mode)

Let me recall that the bug is triggered by connecting to the internet via a
mobile phone, using bluetooth DUN and then disconnecting. Kernel panics on
disconnection (the phone I am using is a Samsung Galaxy S Plus)

- Bug does not happen on the same machines when connecting to the internet via
ppp using a usb gsm/umts dongle and the same provider, so the bug seems to be BT
related and not common to all internet connections using a Point to Point serial
protocol.

Unfortunately, I see the bug on a machine that I use for day by day work and
I cannot afford bisecting here.

Nonetheless, the bug seems easy to reproduce (I catched it on two different
machines with different setups). So I hope this note can help haunting the
regression anyway.

Thanks for the attention,

Sergio Callegari
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