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Date: Mon, 09 Nov 2009 10:57:17 +0100 From: Mike Galbraith <efault@....de> To: ego@...ibm.com Cc: Peter Zijlstra <peterz@...radead.org>, "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org> Subject: Re: specjbb2005 and aim7 regression with 2.6.32-rc kernels On Mon, 2009-11-09 at 15:14 +0530, Gautham R Shenoy wrote: > On Mon, Nov 09, 2009 at 10:15:04AM +0100, Peter Zijlstra wrote: > > 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. > > preempt_disable() guarantees that any cpus won't go offline, since we > use stop_machine() to take CPUs offline. I don't think it provides cover > against new cpus coming online. That's exactly the problem I'm having with newidle. Without that barrier, even with the cpumask_and(), it still balances offline cpus. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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