linux-kernel - Re: [PATCH 1/2] panic: ratelimit panic messages

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Message-ID: <20110105132108.GE10129@elte.hu>
Date:	Wed, 5 Jan 2011 14:21:08 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Don Zickus <dzickus@...hat.com>
Cc:	akpm@...ux-foundation.org, fweisbec@...il.com,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/2] panic:  ratelimit panic messages

* Don Zickus <dzickus@...hat.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>'
> 
> Signed-off-by: Don Zickus <dzickus@...hat.com>
> ---
>  Documentation/kernel-parameters.txt |    6 ++++++
>  kernel/panic.c                      |   30 ++++++++++++++++++++++++++++++
>  2 files changed, 36 insertions(+), 0 deletions(-)

Well, but it's not just panics that can occur repeatedly (in fact panics tend to 
trigger once), but recursive/repeated oopses.

So if we try to do some sort of 'show first crash, rate-limit afterwards' thing (i'm 
still not 100% sure about the wiseness of it) then we should cover all common 
occurances of system panics/crashes.

btw., while printk-delay exists and can serve a similar purpose, it's pretty 
cumbersome for panic ratelimit: it slows down bootups extremely, and it also slows 
down regular, harmless printks.

So having some sort of rate-limit for emitting crash screens may make sense, while 
also preserving the oops counter or at least some other notification that we 'lost' 
messages.

	Ingo
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