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Subject: Re: Problem with cpu_rest() change
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
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	 <20050125090131.GA4986@elte.hu>
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Date: Wed, 26 Jan 2005 10:49:12 +1100
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On Tue, 2005-01-25 at 10:01 +0100, Ingo Molnar wrote:

> it can be bad for the idle task to hold the BKL and to have preemption
> enabled - in such a situation the scheduler will get confused if an
> interrupt triggers a forced preemption in that small window. But it's
> not necessary to keep IRQs disabled after the BKL has been dropped. In
> fact i think IRQ-disabling doesnt have to be done at all, the patch
> below ought to solve this scenario equally well, and should solve the
> PPC side-effects too.
> 
> Tested ontop of 2.6.11-rc2 on x86 PREEMPT+SMP and PREEMPT+!SMP (which
> IIRC were the config variants that triggered the original problem), on
> an SMP and on a UP system.

Excellent, thanks.

Ben.