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

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Date:	Mon, 18 Nov 2013 18:13:40 -0500
From:	Jason Baron <jbaron@...mai.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	"mingo@...nel.org" <mingo@...nel.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

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.

Thanks,

-Jason
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