linux-kernel - Re: [PATCH 0/2] printk vs rq->lock and xtime lock

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Date:	Fri, 8 Aug 2008 10:48:41 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
cc:	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 0/2] printk vs rq->lock and xtime lock



On Fri, 8 Aug 2008, Peter Zijlstra wrote:
> +
> +	local_irq_save(flags);
> +	kws = &__get_cpu_var(kws);
> +	if (!kws->pending) {
> +		call_rcu(&kws->head, __wake_up_klogd);
> +		kws->pending = 1;

In case we have a recursive oops in the RCU paths, I'd think we'd be 
*much* better off with

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

in order to not re-enter the RCU paths again and causing endless oopses 
along with list corruption.

Hmm?

Oh, and I don't see the point of the irqsave/restore in __wake_up_klogd(). 
Or the BUG_ON(), for that matter (even if it ever were to trigger, we'd be 
better off _not_ triggering it - I agree with it in a "verifying the new 
implementation works at all" sense, but not in a "this is actually for 
merging" kind of patch).

			Linus
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