linux-kernel - Re: [PATCH 2/2] i7300

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Message-ID: <49006D85.1050709@linux.intel.com>
Date:	Thu, 23 Oct 2008 14:26:45 +0200
From:	Andi Kleen <ak@...ux.intel.com>
To:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
CC:	Len Brown <lenb@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Henroid, Andrew D" <andrew.d.henroid@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"paulmck@...ibm.com" <paulmck@...ibm.com>
Subject: Re: [PATCH 2/2] i7300_idle driver v1.55


> This should not matter as we can safely remove the module even when
> one or more CPUs are idle. As long as one CPU is running, we are sure
> that throttling is not in effect. And as long as we make sure no one
> is executing the notifier that is going to be rmmoded, we should
> be OK. Say one CPU comes out of the idle later, it wont see the notifier
> in the notifier list anymore, because of RCU in atomic notifier
> and things will work fine. I mean we are not rmmoding the routine
> that enters the idle state. We are just rmmoding the routine that
> Can get called before and after idle routine.

That means there is a ordering dependency between the RCU idle
state getting updated and your code running. That is what I meant with
"very careful with idle". Even if it worked right now would
seem fragile to me.

-Andi
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