Subject: Re: linux-2.6.0-test2: Never using pm_idle (CPU wasting power)
From: Robert Love <rml@tech9.net>
To: Roger Larsson <roger.larsson@skelleftea.mail.telia.com>
Cc: Christian Vogel <vogel@skunk.physik.uni-erlangen.de>,
       linux-kernel@vger.kernel.org
In-Reply-To: <200308010045.08178.roger.larsson@skelleftea.mail.telia.com>
References: <20030731150722.A5938@skunk.physik.uni-erlangen.de>
	 <200308010045.08178.roger.larsson@skelleftea.mail.telia.com>
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Date: 31 Jul 2003 15:58:57 -0700
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On Thu, 2003-07-31 at 15:45, Roger Larsson wrote:

> This smells preemptive kernel, correct?

Doesn't look like anything specific to kernel preemption to me.

But if need_resched() is never zero, the while loop fails, and
schedule() _should_ be reached. So something is fishy here. Looking at
it the other way, however, if schedule() is never called, then
need_resched() will remain non-zero forever. Maybe you mean
need_resched() is never non-zero, i.e., it is always zero?

I think the problem is that there is a race between whatever you are
saying ACPI is doing with pm_idle and the setting of idle. Actually,
that is exactly what you are saying :)

Your fix smells exactly of that. Maybe have APCI set need_resched, so
the loop flips over again?

	Robert Love


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