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

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Date:	Fri, 08 Aug 2008 23:35:20 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>, mingo@...e.hu,
	tglx@...utronix.de, marcin.slusarz@...il.com,
	linux-kernel@...r.kernel.org, David Miller <davem@...emloft.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Paul E McKenney <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] printk: robustify printk

Peter Zijlstra <a.p.zijlstra@...llo.nl> writes:

Hopefully nobody puts a printk into call_rcu now...
Also I'm not sure if there wouldn't be livelocks if someone puts
printk into some other parts of RCU (e.g. each RCU adding more
RCU events -- haven't checked that in detail so I might be wrong)

So you just trade one "hands off" part to another.

> +	kws = &__get_cpu_var(kws);
> +	if (!kws->pending) {
> +		kws->pending = 1;
> +		call_rcu(&kws->head, __wake_up_klogd);

How about a big comment describing why you do this?
And you should add comments to all the new hands-off parts
where printk is not allowed now.

-Andi
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