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

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Date:	Tue, 28 Oct 2014 08:29:00 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	Andi Kleen <ak@...ux.intel.com>, 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>,
	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 Tue, Oct 28, 2014 at 08:22:16AM -0400, Prarit Bhargava wrote:
> 
> 
> On 10/28/2014 08:16 AM, Andi Kleen wrote:
> > 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.
> 
> I suppose ... but that would mean I would have to explain to an end user the
> elaborate process of enabling kdb, inserting a break point, etc.  The whole
> purpose of this is to let an end user panic on WARN() easily.
> 
> Asking an end user to enable kdb is magnitudes worse than asking them to
> recompile a kernel.

Agreed. Asking a customer to setup and run kdb and put breakpoints is much
more pain than simply asking to reboot kernel with a command line option.

Thanks
Vivek
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