Re: [PATCH v2] panic: Make panic_timeout configurable

From: Ingo Molnar
Date: Tue Nov 19 2013 - 02:09:16 EST



* Jason Baron <jbaron@xxxxxxxxxx> wrote:

> On 11/18/2013 05:30 PM, Andrew Morton wrote:
> > On Mon, 18 Nov 2013 21:04:36 +0000 (GMT) Jason Baron <jbaron@xxxxxxxxxx> 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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