From: Johannes Berg <johannes@sipsolutions.net>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev list <linuxppc-dev@ozlabs.org>,
cpufreq <cpufreq@lists.linux.org.uk>,
Ashok Raj <ashok.raj@intel.com>,
davej@codemonkey.org.uk
Subject: Re: CPU hotplug vs. cpufreq on ppc64
Date: Mon, 05 Feb 2007 07:45:51 +0100 [thread overview]
Message-ID: <1170657951.23273.22.camel@johannes.berg> (raw)
In-Reply-To: <1170639556.2620.75.camel@localhost.localdomain>
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On Mon, 2007-02-05 at 12:39 +1100, Benjamin Herrenschmidt wrote:
> So you mean that the policy->cpus mask is lost on unplug/replug ? Hrm...
Yes, but fixing that wouldn't fix the problem.
> I'm not sure what's the best way to restore it. Do we have a cpufreq
> backend callback on hotplug to restore things ?
Not afaict, but you can of course always use register_hotcpu_notifier.
This, however, is what cpufreq.c uses to be notified of a new CPU that
is coming online, and it then calls cpufreq_add_dev which even with a
correct policy->cpus mask wouldn't go back to adding the links back,
this is only done when CPU#0 comes online.
I think this is a more generic problem and code will need to be added to
cpufreq to
(a) call into the cpufreq_driver asking it to update the mask on
hotplug
(b) after that, check the mask and re-link on hotplug.
johannes
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next prev parent reply other threads:[~2007-02-05 6:46 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-01 20:14 CPU hotplug vs. cpufreq on ppc64 Johannes Berg
2007-02-05 1:39 ` Benjamin Herrenschmidt
2007-02-05 6:45 ` Johannes Berg [this message]
2007-02-05 17:13 ` Jacob Shin
2007-02-05 17:33 ` Johannes Berg
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