linux-kernel - Re: [PATCH] cpufreq: powernow-k8: Remove bogus smp_processor

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Message-ID: <20121027191051.GA2693@htj.dyndns.org>
Date:	Sat, 27 Oct 2012 12:10:51 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	stable@...r.kernel.org, Carsten Emde <C.Emde@...dl.org>
Subject: Re: [PATCH] cpufreq: powernow-k8: Remove bogus smp_processor_id()
 usage

Hello, Thomas.

On Sat, Oct 27, 2012 at 07:29:25PM +0200, Thomas Gleixner wrote:
> This is fully preemptible non cpu bound context though the comment in the
> code says:
> 
> 	 * Must run on @pol->cpu.  cpufreq core is responsible for ensuring
> 	 * that we're bound to the current CPU and pol->cpu stays online.
> 
> The core only guarantees that pol->cpu stays online, but it has no way
> to bind the thread and this needs to be fully preemptible context as
> powernowk8_target_fn() calls functions which might sleep.
> 
> So the correct solution is to always go through work_on_cpu().

Yeah, that was stupid.  Rafael already has a patch queued.

  http://git.kernel.org/?p=linux/kernel/git/rafael/linux-pm.git;a=commit;h=e4df1cbcc1f329e53a1fff7450b2229e0addff20

Thanks.

-- 
tejun
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