linux-kernel - Re: [RFC PATCH] kick sleeping idle CPUS on cpu_idle

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Date:	Tue, 8 Jan 2008 04:33:30 +0100
From:	Andi Kleen <ak@...e.de>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>, Andi Kleen <ak@...e.de>,
	"Brown, Len" <len.brown@...el.com>,
	Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>,
	Adam Belay <abelay@...ell.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC PATCH] kick sleeping idle CPUS on cpu_idle_wait

On Mon, Jan 07, 2008 at 09:27:24PM -0500, Steven Rostedt wrote:
> 
> Sometimes cpu_idle_wait gets stuck because it might miss CPUS that are
> already in idle, have no tasks waiting to run and have no interrupts
> going to them.  This is common on bootup when switching cpu idle
> governors.

I must admit I never liked that cpu idle wait code anyways. Why again
can't normal RCU be used for this? Waiting for two RCU quiescent cycles should
be enough, shouldn't it?

-Andi
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