linux-kernel - Re: [PATCH V4] kernel, add bug_on

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Date:	Tue, 28 Oct 2014 05:16:36 -0700
From:	Andi Kleen <ak@...ux.intel.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Fabian Frederick <fabf@...net.be>, vgoyal@...hat.com,
	isimatu.yasuaki@...fujitsu.com, linux-doc@...r.kernel.org,
	kexec@...ts.infradead.org, linux-api@...r.kernel.org,
	jason.wessel@...driver.com
Subject: Re: [PATCH V4] kernel, add bug_on_warn

On Fri, Oct 24, 2014 at 08:53:27AM -0400, Prarit Bhargava wrote:
> There have been several times where I have had to rebuild a kernel to
> cause a panic when hitting a WARN() in the code in order to get a crash
> dump from a system.  Sometimes this is easy to do, other times (such as
> in the case of a remote admin) it is not trivial to send new images to the
> user.
> 
> A much easier method would be a switch to change the WARN() over to a
> BUG().  This makes debugging easier in that I can now test the actual
> image the WARN() was seen on and I do not have to engage in remote
> debugging.

IMHO this would be better and far more generically done with kdb. 
You would need two things:

- Extend the break point command to run another command on a break point.
- Add a command line (or possibly /proc) option to execute some kdb commands at
kernel boot.

Then just set a break point on the warn function and execute magic sysrq c
from kdb.

-Andi
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