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Subject: RE: [PATCH] cpumask: avoid playing with cpus_allowed in powernow-k8.c
Date: Mon, 15 Jun 2009 10:40:09 -0500
Message-ID: <6453C3CB8E2B3646B0D020C112613273036209AB@sausexmb4.amd.com>
In-Reply-To: <200906122055.38203.rusty@rustcorp.com.au>
Thread-Topic: [PATCH] cpumask: avoid playing with cpus_allowed in powernow-k8.c
Thread-Index: AcnrUI5liU+eNxTnT3KeA1vsY1H6sgCftzFA
References: <20090611225928.E6FF4DDDA1@ozlabs.org> <20090611232517.GA32486@redhat.com> <200906122055.38203.rusty@rustcorp.com.au>
From: "Langsdorf, Mark" <mark.langsdorf@amd.com>
To: "Rusty Russell" <rusty@rustcorp.com.au>, "Dave Jones" <davej@redhat.com>
CC: <cpufreq@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
       "Ingo Molnar" <mingo@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1073
Lines: 26

> cpumask: avoid playing with cpus_allowed in powernow-k8.c
>     
> It's generally a very bad idea to mug some process's cpumask: it could
> legitimately and reasonably be changed by root, which could break us
> (if done before our code) or them (if we restore the wrong value).
>     
> I did not replace powernowk8_target; it needs fixing, but it grabs a
> mutex (so no smp_call_function_single here) but Mark points out it can
> be called multiple times per second, so work_on_cpu is too heavy.
>     
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> To: davej@redhat.com
> To: cpufreq@vger.kernel.org
> Cc: mark.langsdorf@amd.com

I ran this over the weekend on a 24 core box without
any issues.  Please commit.

Acked-by: Mark Langsdorf <mark.langsdorf@amd.com>
Tested-by: Mark Langsdorf <mark.langsdorf@amd.com>

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