linux-kernel - Re: unexpected taint message

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Date:	Fri, 16 Dec 2011 08:13:46 -0600
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Johannes Berg <johannes@...solutions.net>
CC:	Arend van Spriel <arend@...adcom.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	John Linville <linville@...driver.com>
Subject: Re: unexpected taint message

On 12/16/2011 07:58 AM, Johannes Berg wrote:
> On Fri, 2011-12-16 at 07:53 -0600, Larry Finger wrote:
>> On 12/16/2011 06:30 AM, Johannes Berg wrote:
>>> On Fri, 2011-12-16 at 10:27 +0100, Arend van Spriel wrote:
>>>> To whoever may know,
>>>>
>>>> Upon loading our driver module I get the following message:
>>>>
>>>> kernel: [  344.805106] Disabling lock debugging due to kernel taint
>>>>
>>>> What exactly are the criteria for tainting? Our driver locking strategy
>>>> is something we want to refactor and having lock debugging during that
>>>> transition may be a life safer.
>>>
>>> cat /proc/sys/kernel/tainted
>>
>> Please note that Documentation/sysctl/kernel.txt is missing the explanation for
>> two bits in the value printed:
>>
>> 2048 - The system is working around a severe firmware bug.
>> 4096 - An out-of-tree module has been loaded.
>>
>> On my system, bit 4096 is set due to loading the VirtualBox module, which
>> disables lock debugging lock debugging. I suspect that loading VMware would
>> cause the same condition.
>
> Hmm. I wish OOT didn't disable lockdep, we do a lot of development with
> modules OOT because the turnaround is faster/easier (for not so
> experienced developers). Worst case we can patch it out of the base
> kernel I guess...

Me too. Now I understand John's patch entitled "[RFC] modpost: add option to 
allow external modules to avoid taint". I doubt that it will be allowed 
upstream, but I think that I will add it as a local commit.

I had failed to notice that the VB module was disabling lock checking, and I 
ACKed a patch to rtlwifi that triggers a nested lock WARNING. Oh well, at least 
the bug was not released into the wild yet.

Larry
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