In-Reply-To: <1106696952.6244.22.camel@gaston>
References: <1106696952.6244.22.camel@gaston>
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Cc: "Linux Kernel list" <linux-kernel@vger.kernel.org>,
       "Andrew Morton" <akpm@osdl.org>, "Ingo Molnar" <mingo@elte.hu>
From: Kumar Gala <kumar.gala@freescale.com>
Subject: Re: Problem with cpu_rest() change
Date: Tue, 25 Jan 2005 23:45:33 -0600
To: "Benjamin Herrenschmidt" <benh@kernel.crashing.org>
Sender: linux-kernel-owner@vger.kernel.org
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Will these changes cause us to back out the patch already made to 
arch/ppc/kernel/idle.c for systems that did not support powersavings?

- kumar

On Jan 25, 2005, at 5:49 PM, Benjamin Herrenschmidt wrote:

> 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.
>
>
>
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