From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"mingo@elte.hu" <mingo@elte.hu>,
"ak@linux.intel.com" <ak@linux.intel.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Jiri Olsa <jolsa@redhat.com>,
"Yan, Zheng" <zheng.z.yan@intel.com>,
Borislav Petkov <bp@alien8.de>,
Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
Subject: Re: [PATCH v6 3/4] perf,x86: add Intel RAPL PMU support
Date: Mon, 11 Nov 2013 17:16:31 +0100 [thread overview]
Message-ID: <20131111161631.GA21461@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CABPqkBRZ84Hc9oAU6zFxNWMv9hT+zMu3Od7_b5fhHRgbG3MXPA@mail.gmail.com>
On Mon, Nov 11, 2013 at 05:07:22PM +0100, Stephane Eranian wrote:
> On Mon, Nov 11, 2013 at 4:59 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Fri, Nov 08, 2013 at 08:46:02PM +0100, Stephane Eranian wrote:
> >
> >
> >> +static DEFINE_SPINLOCK(rapl_hotplug_lock);
> >
> > What is this thing protecting?
> >
> > Like last time it appears to be used only from hotplug notifier
> > callbacks and those are already fully serialized.
> >
> I thought you or somebody else had said, that hotplug in now parallel.
There's a little something about hotplug here I think:
http://marc.info/?l=linux-kernel&m=138118235612441
But I'm not entirely sure that's the origin of this lock.
Andi seems worried about the IPI vs hotplug/migrate. I'm not entrely
sure the lock as proposed actually fixes that.
The 'easy' way would be to put a synchronize_sched() right after the
migrate code, that forces all CPUs to have scheduled once and thus also
ensures all pending/running interrupts are serviced.
But I don't think that's strictly required as I seem to recall hotplug
actually already does something like this -- it pretty much has to.
next prev parent reply other threads:[~2013-11-11 16:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-08 19:45 [PATCH v6 0/4] perf/x86: " Stephane Eranian
2013-11-08 19:46 ` [PATCH v6 1/4] perf: add active_entry list head to struct perf_event Stephane Eranian
2013-11-08 19:46 ` [PATCH v6 2/4] perf stat: add event unit and scale support Stephane Eranian
2013-11-08 19:46 ` [PATCH v6 3/4] perf,x86: add Intel RAPL PMU support Stephane Eranian
2013-11-11 15:59 ` Peter Zijlstra
2013-11-11 16:07 ` Stephane Eranian
2013-11-11 16:16 ` Peter Zijlstra [this message]
2013-11-12 14:14 ` Stephane Eranian
2013-11-12 15:02 ` Andi Kleen
2013-11-08 19:46 ` [PATCH v6 4/4] perf,x86: add RAPL hrtimer support Stephane Eranian
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