Re: [PATCH v2] panic: Make panic_timeout configurable

[Michael Ellerman <mpe@ellerman.id.au>]

On Tue, Nov 19, 2013 at 05:04:14PM -0500, Jason Baron wrote:
> On 11/19/2013 02:09 AM, Ingo Molnar wrote:
> > 
> > * Jason Baron <jbaron@akamai.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@akamai.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.
...
> 
> Sure, I can round up all the related patches in this area that make
> sense and re-submit as a series.
> 
> Felipe, would the CONFIG_PANIC_TIMEOUT=xx .config parameter work for your
> needs, or would you still like to see the command-line processing moved
> up?
> 
> I'd also like to hear from the PowerPC folks about the arch defaults
> there. Now, that mips is ok with CONFIG_PANIC_TIMEOUT, PowerPC is the
> only arch doing specific initialization of 'panic_timeout'.

Hi Jason,

I think we'd like to choose the value at runtime, as we do now. The
powerpc arch supports a wide spread of different hardware, so it's nice
to be able to customise the value based on the platform. Also we build a
single kernel that boots on many platforms, and so we can't pick the
value at compile time.

cheers