Messages in this thread |  | | Subject | Re: [RFC 09/11] coresight: etm-perf: Disable the path before capturing the trace data | From | Suzuki K Poulose <> | Date | Thu, 12 Nov 2020 09:27:56 +0000 |
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On 11/10/20 12:45 PM, Anshuman Khandual wrote: > perf handle structure needs to be shared with the TRBE IRQ handler for > capturing trace data and restarting the handle. There is a probability > of an undefined reference based crash when etm event is being stopped > while a TRBE IRQ also getting processed. This happens due the release > of perf handle via perf_aux_output_end(). This stops the sinks via the > link before releasing the handle, which will ensure that a simultaneous > TRBE IRQ could not happen. > > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > This might cause problem with traditional sink devices which can be > operated in both sysfs and perf mode. This needs to be addressed > correctly. One option would be to move the update_buffer callback > into the respective sink devices. e.g, disable(). > > drivers/hwtracing/coresight/coresight-etm-perf.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index 534e205..1a37991 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -429,7 +429,9 @@ static void etm_event_stop(struct perf_event *event, int mode) > > size = sink_ops(sink)->update_buffer(sink, handle, > event_data->snk_config); > + coresight_disable_path(path); > perf_aux_output_end(handle, size); > + return; > }
As you mentioned, this is not ideal where another session could be triggered on the sink from a different ETM (not for per-CPU sink) in a different mode before you collect the buffer. I believe the best option is to leave the update_buffer() to disable_hw. This would need to pass on the "handle" to the disable_path.
That way the races can be handled inside the sinks. Also, this aligns the perf mode of the sinks with that of the sysfs mode.
Suzuki
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