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

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Message-ID: <48f7fe350807132110k4cd90e9j6907674ea7668f5b@mail.gmail.com>
Date:	Mon, 14 Jul 2008 00:10:50 -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

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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