From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Robert Richter <rric@kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mike Galbraith <efault@gmx.de>, Paul Mackerras <paulus@samba.org>,
Stephane Eranian <eranian@google.com>,
Andi Kleen <ak@linux.intel.com>,
kan.liang@intel.com, adrian.hunter@intel.com,
markus.t.metzger@intel.com, mathieu.poirier@linaro.org,
acme@infradead.org
Subject: Re: [PATCH v8 12/14] x86: perf: intel_pt: Intel PT PMU driver
Date: Tue, 13 Jan 2015 17:27:20 +0100 [thread overview]
Message-ID: <20150113162720.GL25256@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <87sifen2d5.fsf@ashishki-desk.ger.corp.intel.com>
On Tue, Jan 13, 2015 at 05:09:58PM +0200, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > On Fri, Nov 14, 2014 at 03:43:45PM +0200, Alexander Shishkin wrote:
> >> +static void pt_event_stop(struct perf_event *event, int mode)
> >> +{
> >> + struct pt *pt = this_cpu_ptr(&pt_ctx);
> >> +
> >> + ACCESS_ONCE(pt->handle_nmi) = 0;
> >
> > Why is this needed? Will the hardware still generate interrupts if you
> > stop the PT thing?
>
> Actually, it turns out that the interrupt condition can race with the
> wrmsr that disables tracing and the PT bit remains set in the global
> status register, causing the next PMI to go into the PT PMI handler,
> which then may decide to re-enable the counter that should be disabled.
OK, please add this information in a suitably placed comment.
Thanks!
next prev parent reply other threads:[~2015-01-13 16:27 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-14 13:43 [PATCH v8 00/14] perf: Add infrastructure and support for Intel PT Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 01/14] perf: Add data_{offset,size} to user_page Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 02/14] perf: Add AUX area to ring buffer for raw data streams Alexander Shishkin
2014-11-17 9:33 ` Metzger, Markus T
2015-01-09 15:18 ` Peter Zijlstra
2015-01-12 13:12 ` Alexander Shishkin
2015-01-12 13:38 ` Peter Zijlstra
2015-01-12 14:00 ` Alexander Shishkin
2014-11-17 21:24 ` Sukadev Bhattiprolu
2014-11-17 21:45 ` Andi Kleen
2014-11-14 13:43 ` [PATCH v8 03/14] perf: Support high-order allocations for AUX space Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 04/14] perf: Add a capability for AUX_NO_SG pmus to do software double buffering Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 05/14] perf: Add a pmu capability for "exclusive" events Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 06/14] perf: Add AUX record Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 07/14] perf: Add api for pmus to write to AUX area Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 08/14] perf: Support overwrite mode for " Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 09/14] perf: Add wakeup watermark control to " Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 10/14] x86: Add Intel Processor Trace (INTEL_PT) cpu feature detection Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 11/14] x86: perf: Intel PT and LBR/BTS are mutually exclusive Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 12/14] x86: perf: intel_pt: Intel PT PMU driver Alexander Shishkin
2015-01-09 12:48 ` Peter Zijlstra
2015-01-12 12:19 ` Alexander Shishkin
2015-01-13 15:09 ` Alexander Shishkin
2015-01-13 16:27 ` Peter Zijlstra [this message]
2015-01-09 13:10 ` Peter Zijlstra
2015-01-12 12:45 ` Alexander Shishkin
2015-01-09 14:09 ` Peter Zijlstra
2015-01-12 12:53 ` Alexander Shishkin
2015-01-12 16:37 ` Alexander Shishkin
2015-01-12 16:40 ` Peter Zijlstra
2014-11-14 13:43 ` [PATCH v8 13/14] x86: perf: intel_bts: Add BTS " Alexander Shishkin
2014-11-14 13:43 ` [PATCH v8 14/14] perf: add ITRACE_START record to indicate that tracing has started Alexander Shishkin
2015-01-09 14:12 ` Peter Zijlstra
2015-01-09 14:13 ` Peter Zijlstra
2015-01-12 9:30 ` Adrian Hunter
2014-12-17 14:06 ` [PATCH v8 00/14] perf: Add infrastructure and support for Intel PT Alexander Shishkin
2015-01-07 9:32 ` Alexander Shishkin
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