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

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Message-ID: <48f7fe350807132112g536f4d2cte9ff2b9dc9c5db6a@mail.gmail.com>
Date:	Mon, 14 Jul 2008 00:12:05 -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

i forgot to mention that my system did not die, i was compiling a
kernel at the time and the compile froze, but i was able to cancel it
and restart the compile, my system stayed alive

On Mon, Jul 14, 2008 at 12:10 AM, 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
>
> -Ryan
>
> On Sun, Jul 13, 2008 at 11:36 PM, Eduard - Gabriel Munteanu
> <eduard.munteanu@...ux360.ro> wrote:
>> On Sun, 13 Jul 2008 19:57:37 -0400
>> "Ryan Hope" <rmh3093@...il.com> wrote:
>>
>>> However, this causes the kernel to crash or oops under certain loads.
>>> Reverting this change makes the error go away. Is there any sort of
>>> performance difference between BUG_ON and WARN_ON_ONCE, I figure the
>>> change was for a reason so I am wondering what will result from this
>>> change. Any info would be appreciated.
>>>
>>> -Ryan
>>
>> Looks like WARN_ON_ONCE declares and uses a static int variable, so
>> it's not reentrant. It should be an atomic static. Still, I don't see
>> how this could crash the kernel or even oops, or have any other
>> side-effects.
>>
>> Could you post the oops? Are you sure the oops you're seeing isn't just
>> what WARN_ON et al. regularly produce?
>>
>>
>>        Eduard
>>
>
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