linux-kernel - Re: [PATCH] printk: robustify printk

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Date:	Mon, 11 Aug 2008 10:55:42 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Valdis.Kletnieks@...edu, Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, tglx@...utronix.de,
	marcin.slusarz@...il.com, linux-kernel@...r.kernel.org,
	davem@...emloft.net, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH] printk: robustify printk

On Mon, 11 Aug 2008, Andi Kleen wrote:

> $INSERT-ANY-OTHER-PRINTK-USE$
> 
> The point was that printk may have been perfectly adequate for 
> them with its existing buffer sizes and dynamic wake up frequency,
> and might not anymore with the timer wakeup change. Essentially
> it is making a widely used kernel facility more fragile.

I've measured several latencies in the kernel that would cause klogd to 
take serveral jiffies to wake up. I highly doubt that adding one jiffy 
will break anything. And if it did, then it would show a bug in their 
system. If adding one jiffy causes lost data, then the system 
administrators are relying on a utility (klogd) that can easily fail them 
without these patches.

If we are making a highly fragile setup a bit more fragile, maybe it will 
wake the IT guys up to change their setup.

-- Steve

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