Re: rt2x00: rt2800usb causing kernel panic /compat-wireless/

[Mohammed Shafi <shafi.wireless@gmail.com>]

On Wed, May 18, 2011 at 8:11 PM, Larry Finger <Larry.Finger@lwfinger.net> wrote:
> On 05/18/2011 08:04 AM, Mohammed Shafi wrote:
>>
>> On Wed, May 18, 2011 at 6:21 PM, Gertjan van Wingerde
>> <gwingerde@gmail.com>  wrote:
>>>
>>> On 05/18/11 14:41, Mohammed Shafi wrote:
>>>>
>>>> On Wed, May 18, 2011 at 5:26 PM, Walter Goldens
>>>> <goldenstranger@yahoo.com>  wrote:
>>>>>>>
>>>>>>> A very peculiar bug.
>>>>>>>
>>>>>>> With compat-wireless from 16.05 a nasty bug started to
>>>>>>
>>>>>> manifest itself. Right around association time, the
>>>>>> rt2800usb causes kernel panic. The system freezes and the
>>>>>> Caps Lock and Num Lock leds on the keyboard begin to flash.
>>>>>>
>>>>>> also ath9k, iwlagn.
>>>>>>
>>>>>>>
>>>>>>> Unfortunately there are no recoverable traces after
>>>>>>
>>>>>> the system failure to aid this bug report or to indicate its
>>>>>> origin.
>>>>>>>
>>>>>>> I believe it may somehow be related to Ubuntu's
>>>>>>
>>>>>> network-manager. If I turn off the network-manager service,
>>>>>> I can go into monitor mode for example, but if
>>>>>> network-manager is running and I plug my USB dongle, it
>>>>>> starts to associate, a second or two later the system is in
>>>>>> complete meltdown.
>>>>>>
>>>>>> same thing, monitor mode worked perfectly fine.
>>>>>>
>>>>>>>
>>>>>>> Nothing concrete, but a hunch is telling me this has
>>>>>>
>>>>>> something to do with the association mechanism of the
>>>>>> rt2800usb. Compat-wireless from few days back exhibits no
>>>>>> such foul play.
>>>>>>
>>>>>> yes just right at the association complete freeze.
>>>>>>
>>>>>
>>>>> That's strange. I wonder what's the connection with this bug and
>>>>> network-manager. Because when I manually tried to associate, dmesg reported
>>>>> the association attempt timed out.
>>>>
>>>> no even when we use iw dev connect command we can see the panic.
>>>
>>> Yeah, I've seen this freeze as well using one of the later
>>> compat-wireless packages using just iw and wpa_supplicant to bring up the
>>> card. This is on all sorts of rt2x00 supported devices.
>>>
>>> However, I don't believe this to be an rt2x00-specific bug, as exactly
>>> the same rt2x00 sources inside a compat-wireless-2.6.39rc7 package do not
>>> produce the freeze.
>>>
>>>> some expert suspected that there is a chance of kfree_rcu in
>>>> compat-wireless may have caused the problem
>>>>
>>>
>>> That's where my suspicion is as well, but I didn't have the time to
>>> further investigate. Since my focus was on rt2x00 I used the
>>> compat-wireless-2.6.39rc7 package to test my patches. I only did a quick
>>> check, and the kfree_rcu compatibility fix that was done in compat-wireless
>>> did seem to match the kfree_rcu code is present in linux-next, but maybe
>>> there is an odd side-effect.
>>
>> I could not exactly remember this panic came just after kfree_rcu
>> backported..
>
> This problem also occurs with rtl8192se from compat-wireless. When it was
> reported to me, a photo of the console log was included (attached). The
> crash is a NULL pointer in rcu_do_batch.clone.19 (I think - the photo
> quality is minimal.).

thanks!, same type of call trace which I had also obtained, hopefully there in
 http://pastebin.com/CZrSZrme
 http://pastebin.com/gwZJGDG4



>
> Larry
>
>
>
>



-- 
shafi