linux-kernel - Re: [PATCH] acpi, cpuidle: Register with cpuidle even if cpu is onlined after boot (beyond maxcpus)

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Date:	Tue, 26 Jun 2012 13:01:25 +0200
From:	Thomas Renninger <trenn@...e.de>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	linux-acpi@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Linux PM mailing list <linux-pm@...r.kernel.org>,
	lenb@...nel.org, "Rafael J. Wysocki" <rjw@...k.pl>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] acpi, cpuidle: Register with cpuidle even if cpu is onlined after boot (beyond maxcpus)

On Tuesday, June 26, 2012 12:42:14 PM Daniel Lezcano wrote:
> On 06/26/2012 11:58 AM, Srivatsa S. Bhat wrote:
> > On 06/26/2012 03:11 PM, Daniel Lezcano wrote:
> >> On 06/26/2012 11:29 AM, Thomas Renninger wrote:
...
> >>
> >> In this case, let's remove the intel_idle_cpu_init stuff in
> >> acpi_cpu_soft_notify, no ?
> >>
> > 
> > Why? And how would that help? The intel_idle_cpu_init() call is essential if intel_idle
> > driver is being used instead of acpi idle.
> 
> AFAIU, this code is not called after onlining a cpu greater than maxcpus
> and Thomas thinks that system with cpu hotplug at runtime are not sold.
Not 100% sure. Also the code paths to handle real CPU hotplug existed
already (via ACPI notify on the processor object) and did work.
I only fixed to correctly initialize idle states.

> The problem I see with this code is acpi and intel-idle are tied
> together now. I would like to break this dependency and use the notifier
> to handle the cpu hotplug directly in intel-idle.
> 
> It is hard to test my patch as there is not such system and maxcpus is
> not correctly handled here. I can use your patch to test my patch but
> anyway ... I am just asking if that would make sense to remove this
> portion of code instead :)
> 
> If we want to keep this code untouched, I can try my patch and maybe
> Thomas will agreed to test it also on a cpu-online-runtime-system if he
> has one.
But not this patch, we agreed it's not worth to look at:
"System exceeding maxcpus=x via cpu soft onlining does not initialize
power management on exceeding cores", right?

If you have a patch touching this, please point me to it.
I can have a look at it and if really necessary give it a test.

   Thomas
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