linux-kernel - Re: [PATCH] power: Change device_wakeup_enable() to check for null dev

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Message-id: <528A5233.4040306@samsung.com>
Date:	Mon, 18 Nov 2013 10:45:23 -0700
From:	Shuah Khan <shuah.kh@...sung.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>, anton@...msg.org,
	dwmw2@...radead.org
Cc:	len.brown@...el.com, pavel@....cz, gregkh@...uxfoundation.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	shuahkhan@...il.com, stable@...r.kernel.org,
	Shuah Khan <shuah.kh@...sung.com>
Subject: Re: [PATCH] power: Change device_wakeup_enable() to check for null
 dev_name(dev)

On 11/15/2013 05:32 PM, Rafael J. Wysocki wrote:
> On Friday, November 15, 2013 05:16:31 PM Shuah Khan wrote:
>> On 11/15/2013 05:21 PM, Rafael J. Wysocki wrote:
>>> On Friday, November 15, 2013 05:03:57 PM Shuah Khan wrote:
>>>> device_wakeup_enable() uses dev_name(dev) as the wakeup source name.
>>>> When it gets called with a device with its name not yet set, ws structure
>>>> with ws->name = NULL gets created.
>>>>
>>>> When kernel is booted with wakeup_source_activate enabled, it will panic
>>>> when the trace point code tries to derefernces ws->name.
>>>>
>>>> Change device_wakeup_enable() to check for dev_name(dev) null condition
>>>> and return -EINVAL to avoid panics when device_wakeup_enable() gets called
>>>> before device is fully initialized with its name.
>>    		return -EINVAL;
>>>
>>> Can you please use WARN_ON(!dev_name(dev)) here?  While I agree that it is a
>>> bad idea to crash the kernel because dev has no name, that indicates a driver
>>> bug that shouldn't be too easy to ignore.
>>>
>>> Thanks!
>>>
>>
>> Right. ok I will re-cut the patch with WARN_ON and send it. fyi I did
>> send fix for the driver (power_supply) as well.
>>
>> http://www.kernelhub.org/?msg=362354&p=2
>
> That's OK (thanks for taking care of this), but there may be more brilliant
> stuff like that in the future and people should see right away that something's
> wrong in those cases.
>

Rafael/Anton/David,

I added WARN_ON and testing the patch. We have two instance of 
device_wakeup_enable() calls with null dev_name during boot. Both are 
from power_supply_register(). One when AC Adapter [ADP1] is added and 
the second when device: 'BAT1' gets added.

[    4.412959] device_wakeup_enable() called with null device nme
[    4.412967] device: 'ADP1': device_add

[    4.460190] device_wakeup_enable() called with null device nme
[    4.460197] device: 'BAT1': device_add


I think adding WARN_ON to device_wakeup_enable() and fix to 
power_supply_register() should go in as a dependent patch series, to 
avoid panics during boot. As soon as the device_wakeup_enable() WARN_ON 
goes in, I suspect most laptops will panic during boot, similar to what 
  I am seeing in my testing. Thoughts?

I will send these fixes, maybe these two can be funneled through PM tree 
with power_supply maintainers ACK for the power_supply_register() fix.

thanks,
-- Shuah

-- 
Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley)
shuah.kh@...sung.com | (970) 672-0658
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