linux-kernel - Re: Performance Question: BUG_ON vs. WARN_ON

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Message-ID: <48f7fe350807132151udc3a462g688336a9fab7b768@mail.gmail.com>
Date:	Mon, 14 Jul 2008 00:51:09 -0400
From:	"Ryan Hope" <rmh3093@...il.com>
To:	"Eduard - Gabriel Munteanu" <eduard.munteanu@...ux360.ro>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Nick Piggin" <nickpiggin@...oo.com.au>
Subject: Re: Performance Question: BUG_ON vs. WARN_ON_ONCE

radeon drm/dri is opensource, i use the radeonhd driver for xorg

On Mon, Jul 14, 2008 at 12:36 AM, Eduard - Gabriel Munteanu
<eduard.munteanu@...ux360.ro> wrote:
> On Mon, 14 Jul 2008 00:10:50 -0400
> "Ryan Hope" <rmh3093@...il.com> wrote:
>
>> well the bug I recieved looked like it had to do with highmem and this
>> was the only code relating to mem that got touched, as for the other
>> person, their crash was reproducible and it definitely was an oops,
>> numlock led started to blink and system was unresponsive, for both of
>> us
>> reverting this change seems fix the issue, my dmesg log is attached to
>> this message
>
> There are a few things you should take into account before anything else:
> 1. The bug does not occur there, but in other code.
> 2. The kernel is tainted.
> 3. The oopses start occuring just after you load that tainted module,
> or at least something related (that drm stuff is linked to the radeon
> module, I presume, which is proprietary AFAIK)
>
> So you should retest after eliminating all these possible noise and
> error sources. Test both if your fix (revert) is correct and if it
> crashes without your fix.
>
> My guess is that would've happened sooner or later and your fix just
> moved stuff around enough to mask it. That static int from WARN_ON_ONCE
> means another 4 or 8 bytes in the kernel image, which might set things
> off in an already unstable environment.
>
>
>        Eduard
>
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