linux-kernel - Re: [PATCH v2] panic: Make panic

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Date:	Tue, 19 Nov 2013 08:09:05 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Jason Baron <jbaron@...mai.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	"paulus@...ba.org" <paulus@...ba.org>,
	"ralf@...ux-mips.org" <ralf@...ux-mips.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Felipe Contreras <felipe.contreras@...il.com>
Subject: Re: [PATCH v2] panic: Make panic_timeout configurable


* Jason Baron <jbaron@...mai.com> wrote:

> On 11/18/2013 05:30 PM, Andrew Morton wrote:
> > On Mon, 18 Nov 2013 21:04:36 +0000 (GMT) Jason Baron <jbaron@...mai.com> wrote:
> > 
> >> The panic_timeout value can be set via the command line option 'panic=x', or via
> >> /proc/sys/kernel/panic, however that is not sufficient when the panic occurs
> >> before we are able to set up these values. Thus, add a CONFIG_PANIC_TIMEOUT
> >> so that we can set the desired value from the .config.
> >>
> >> The default panic_timeout value continues to be 0 - wait forever, 
> >> except for powerpc and mips, which have been defaulted to 180 and 
> >> 5 respectively. This is in keeping with the fact that these 
> >> arches already set panic_timeout in their arch init code. 
> >> However, I found three exceptions- two in mips and one in powerpc 
> >> where the settings didn't match these default values. In those 
> >> cases, I left the arch code so it continues to override, in case 
> >> the user has not changed from the default. It would nice if these 
> >> arches had one default value, or if we could determine the 
> >> correct setting at compile-time.
> > 
> > Felipe is proposing a simpler patch ("panic: setup panic_timeout 
> > early") which switches to early_param().  Is that sufficient for 
> > the (undescribed!) failure which you are presumably observing?
> > 
> 
> No - that patch doesn't change the 'panic_timeout' value until the 
> call to 'parse_early_param()' is made. If there is a panic before 
> that point, the param doesn't do anything. The idea of this patch is 
> to allow it to be configured at build-time.
> 
> I've tested the patch by simply inserting a panic() call at the 
> beginning of 'start_kernel()'. So, no I do not have a specific panic 
> in mind for this.

Would you be interested in picking up Felipe's patch/fix on top of 
yours? I was unable to communicate with him efficiently, but I'd take 
the patch if it's signed off by you.

Thanks,

	Ingo
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