linux-kernel - Re: [PATCH V6 07/13] perf: Generic pci uncore device support

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Date:	Mon, 18 Jun 2012 09:43:08 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
Cc:	mingo@...e.hu, jolsa@...hat.com, eranian@...gle.com,
	andi@...stfloor.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 07/13] perf: Generic pci uncore device support

On Mon, 2012-06-18 at 11:06 +0800, Yan, Zheng wrote:
> On 06/16/2012 12:02 AM, Peter Zijlstra wrote:
> > On Fri, 2012-06-15 at 14:31 +0800, Yan, Zheng wrote:
> >> @@ -305,6 +310,22 @@ struct intel_uncore_box *uncore_alloc_box(int cpu)
> >>  static struct intel_uncore_box *
> >>  uncore_pmu_to_box(struct intel_uncore_pmu *pmu, int cpu)
> >>  {
> >> +       static struct intel_uncore_box *box;
> >> +
> >> +       box =  *per_cpu_ptr(pmu->box, cpu);
> >> +       if (box)
> >> +               return box;
> >> +
> >> +       raw_spin_lock(&uncore_box_lock);
> >> +       list_for_each_entry(box, &pmu->box_list, list) {
> >> +               if (box->phys_id == topology_physical_package_id(cpu)) {
> >> +                       atomic_inc(&box->refcnt);
> >> +                       *per_cpu_ptr(pmu->box, cpu) = box;
> >> +                       break;
> >> +               }
> >> +       }
> >> +       raw_spin_unlock(&uncore_box_lock);
> >> +
> >>         return *per_cpu_ptr(pmu->box, cpu);
> >>  } 
> > 
> > So why can't we do that lookup from a hotplug notifier?
> > 
> We can. But I personally prefer not to mix pci uncore initialization
> code with cpu hotplug notifier. Because pci hotplug and cpu hotplug
> are separate process, I'm not completely sure which one happens first.

I suspect nobody does.. OK we'll leave it as it is. Thanks
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