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Subject: Re: specjbb2005 and aim7 regression with 2.6.32-rc kernels
From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <efault@gmx.de>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>,
       Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>,
       Gautham R Shenoy <ego@in.ibm.com>
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Date: Mon, 09 Nov 2009 10:15:04 +0100
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On Mon, 2009-11-09 at 08:09 +0100, Mike Galbraith wrote:
> +       smp_read_barrier_depends();
>         cpumask_setall(cpus);
> +       cpumask_and(cpus, cpus, cpu_online_mask);


how about: cpumask_copy(cpus, cpu_online_mask); ?

Also, iirc cpu_online_mask is guaranteed stable when preemption is
disabled, otherwise you need to use get/put_online_cpus(), an
rmb_depends() won't do.