linux-kernel - Re: [PATCH 2/3] perf_events: fix validation of events using an extra reg (v4)

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Date:	Thu, 09 Jun 2011 22:48:47 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Lin Ming <ming.m.lin@...el.com>
Subject: Re: [PATCH 2/3] perf_events: fix validation of events using an
 extra reg (v4)

On Thu, 2011-06-09 at 22:36 +0200, Stephane Eranian wrote:
> On Thu, Jun 9, 2011 at 8:40 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Mon, 2011-06-06 at 16:57 +0200, Stephane Eranian wrote:
> >> +static struct cpu_hw_events *allocate_fake_cpuc(void)
> >> +{
> >> +       struct cpu_hw_events *cpuc;
> >> +       int cpu = smp_processor_id();
> >
> > That's a boo-boo, clearly we are in a preemptible context here (see the
> > GFP_KERNEL allocation on the next line), so using smp_processor_id()
> > isn't valid.
> >
> Good point. I missed that.

Yeah, I did too, Ingo found it during testing.

> > Now since all that allocate_shared_regs() does with it is pick a NUMA
> > node, we should probably use raw_smp_processor_id() and leave it at
> > that, right?
> >
> Yeah, for what we do with fake_cpuc, it does not really matter where
> it comes from. This is not on any critical path. The simplest allocator
> will do it.

OK, fixed that up.

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