linux-kernel - Re: [PATCH] media: au0828: Convert BUG_ON to WARN

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Message-ID: <4F82468E.5000308@lwfinger.net>
Date:	Sun, 08 Apr 2012 21:16:46 -0500
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Devin Heitmueller <dheitmueller@...nellabs.com>
CC:	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Hans Verkuil <hans.verkuil@...co.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	jrh <jharbestonus@...il.com>
Subject: Re: [PATCH] media: au0828: Convert BUG_ON to WARN_ONCE

On 04/08/2012 08:46 PM, Devin Heitmueller wrote:
> On Sun, Apr 8, 2012 at 7:19 PM, Larry Finger<Larry.Finger@...inger.net>  wrote:
>> In the mail thread at http://www.mythtv.org/pipermail/mythtv-users/2012-April/331164.html,
>> a kernel crash is triggered when trying to run mythtv with a HVR950Q tuner.
>> The crash condition is due to res_free() being called to free something that
>> has is not reserved. The actual reason for this mismatch of reserve/free is
>> not known; however, using a BUG_ON rather than a WARN_ON seems unfortunate.
>
> This patch should be nack'd.  The real reason should be identified,
> and a patch should be submitted for that (and from what I gather, it
> seems like it is easily reproduced by the submitter).  Just add a few
> "dump_stack()" calls in the res_get() and res_free() calls to identify
> the failing call path.

I agree that we need to find the real cause; however, I am not the one with the 
problem, and I do not have the hardware. In addition, I am not sure how much 
additional debug information the person will be able to provide. He has not 
built Linux kernels since 1.2. If he can get a kernel built, then we will try to 
find the real cause.

In any case, why the reluctance to get rid of the BUG_ON? Is this condition so 
severe that the kernel needs to be stopped immediately?

Larry
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