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Date: Fri, 17 Jul 2015 13:40:44 -0400
Subject: Re: Kernel Oops: btusb: 4.2rc1 System lockup with BT dongle insert -
 log attached
From: simon@mungewell.org
To: "Laura Abbott" <labbott@redhat.com>,
        "Shuah Khan" <shuahkh@osg.samsung.com>
Cc: "Kim, Milo" <milo.kim@ti.com>, linux-bluetooth@vger.kernel.org,
        linux-kernel@vger.kernel.org
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> On 07/17/2015 08:14 AM, simon@mungewell.org wrote:
>>
>>>> So in summary this problem is showing up now as the 'User Helper
>>>> Fallback'
>>>> is now forced on, obviously the underlying problem needs to be fixed -
>>>> but
>>>> I don't know when it crept in.
>>>>
>>>
>>> The 'CONFIG_FW_LOADER_USER_HELPER_FALLBACK' enables to load firmware
>>> data manually by accessing /sys/class/firmware/<name>/data. It runs in
>>> case the firmware file is missing.
>>> This user helper fallback will be enabled if one of LP55xx driver is
>>> included in your dot config. Please see my patch below.
>>>
>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/leds?id=b67893206fc0a0e8af87130e67f3d8ae553fc87c
>>>
>>> However, I'm not sure why this affects your system lockup. Can I have
>>> more details?
>>
>> Hi Milo,
>> I'm not suggesting that your patch is the cause, just that it is an
>> 'enabler' and and explains why the problem (system lockup when I plug
>> USB
>> Bluetooth dongle in) appears now.
>>
>> A full Oops log is further back in this thread:
>> http://www.spinics.net/lists/linux-bluetooth/msg63090.html
>>
>>
>>>> Will try building 4.1 with this option to see if it fails.
>>
>> A very quick test as I was leaving the house this morning shows that 4.1
>> with 'CONFIG_FW_LOADER_USER_HELPER_FALLBACK' does not show the problem.
>>
>> So at least we know the 'real' problem is a recent change to the code.
>> Simon
>>
>
> I think this was reported and fixed
>
> https://lkml.org/lkml/2015/7/8/858
> https://lkml.org/lkml/2015/7/8/1199
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6f957724b94cb19f5c1c97efd01dd4df8ced323c
>

Certainly looks like a plausible solution, will build kernel tonight to
confirm.

If  Shuah is still looking for the trigger, see above note regarding
'CONFIG_FW_LOADER_USER_HELPER_FALLBACK'.

Thanks, and have an awesome weekend. :-)
Simon

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