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SubjectRe: [PATCH 1/2] panic: ratelimit panic messages
On Wed, Jan 05, 2011 at 02:51:28PM -0800, Andrew Morton wrote:
> On Tue, 4 Jan 2011 22:38:30 -0500
> Don Zickus <dzickus@redhat.com> wrote:
>
> > Sometimes when things go bad, so much spew is coming on the console it is hard
> > to figure out what happened. This patch allows you to ratelimit the panic
> > messages with the intent that the first panic message will provide the info
> > we need to figure out what happened.
> >
> > Adds new kernel param 'panic_ratelimit=on/<integer in seconds>'
> >
>
> Terminological whinge: panic() is a specific kernel API which ends up
> doing a sort-of-oops thing. So the graph is
>
> panic -> oops
> other-things -> oops
>
> Your patch doesn't affect only panics - it also affects oops, BUG(),
> etc. So I'd suggest that this patch should do s/panic/oops/g.

Ok. Sorry about that.

<snip>
>
> We keep on hacking away at this and things never seem to get much
> better. It's still the case that a large number of our oops reports
> are damaged because the important parts of the oops trace scrolled off
> the screen.
>
> I therefore propose
>
> oops_lines_delay=N,M
>
> which will cause the kernel to pause for M milliseconds after emitting
> N lines of oops output. Bonus marks for handling linewrap!
>
> Start the line counter at oops_begin() or thereabouts and then do the
> delay after N lines have been emitted. I guess that counter should
> _not_ be invalidated in oops_end(): if the oops generates 12 lines and
> then another 100 lines of random printk crap are printed, we still want
> to put a pause after the 13th line of that random crap, so we can view
> the oops.
>
> The oops_lines_delay implemetnation should count lines from all CPUs
> and should block all CPUs during the delay.
>
> I think this would solve the problem which you're seeing, as well as
> the much larger my-oops-scrolled-off problem?

Ok. Forgive me for being thick. I seem to be lost in the lower layer of
the oops code for some reason. I understand your idea and am willing to
take a crack at implementing it, I just can't figure out what function to
stick it in. I grep'd for oops_begin() and it seemed to be an x86-only
thing. Is there a more generic place to put this stuff?

Cheers,
Don

>


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