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Subject: Re: [RFC][PATCH 2/9] perf: core, remove hw_perf_event_init
From: Peter Zijlstra <peterz@infradead.org>
To: Lin Ming <ming.m.lin@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Frederic Weisbecker <fweisbec@gmail.com>,
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Date: Mon, 10 May 2010 12:19:29 +0200
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On Mon, 2010-05-10 at 18:17 +0800, Lin Ming wrote:
> On Mon, 2010-05-10 at 17:40 +0800, Peter Zijlstra wrote:
> > On Mon, 2010-05-10 at 17:26 +0800, Lin Ming wrote:
> > > +static struct pmu *perf_event_lookup_pmu(struct perf_event *event)
> > > +{
> > > +       struct pmu *pmu;
> > > +       int pmu_id = event->attr.pmu_id;
> > > +
> > > +       list_for_each_entry(pmu, &pmus, entry) {
> > > +               if (pmu->id == pmu_id)
> > > +                       return pmu;
> > > +       }
> > > +
> > > +       return NULL;
> > > +}
> > 
> > > +void perf_event_register_pmu(struct pmu *pmu)
> > > +{
> > > +       pmu->id = pmu_id_curr++;
> > > +       list_add_tail(&pmu->entry, &pmus);
> > > +} 
> > 
> > That will be wanting some sort of synchronization
> 
> Will add a mutex to protect the list of pmus.

I'm thinking RCU might be better suited, a mutex for lookup doesn't
sound ideal.