Messages in this thread Patch in this message |  | | Subject | Re: [PATCH v2 03/10] coresight: etm-pmu: Ensure the AUX handle is valid | From | Anshuman Khandual <> | Date | Fri, 30 Jul 2021 09:44:31 +0530 |
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On 7/23/21 6:16 PM, Suzuki K Poulose wrote: > The ETM perf infrastructure closes out a handle during event_stop > or on an error in starting the event. In either case, it is possible > for a "sink" to update/close the handle, under certain circumstances. > (e.g no space in ring buffer.). So, ensure that we handle this > gracefully in the PMU driver by verifying the handle is still valid. > > Cc: Mathieu Poirier <mathieu.poirier@linaro.org> > Cc: Mike Leach <mike.leach@linaro.org> > Cc: Anshuman Khandual <anshuman.khandual@arm.com> > Cc: Leo Yan <leo.yan@linaro.org> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> > --- > .../hwtracing/coresight/coresight-etm-perf.c | 27 ++++++++++++++++--- > 1 file changed, 24 insertions(+), 3 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index 6f398377fec9..a6ab603afee4 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -450,8 +450,15 @@ static void etm_event_start(struct perf_event *event, int flags) > fail_disable_path: > coresight_disable_path(path); > fail_end_stop: > - perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED); > - perf_aux_output_end(handle, 0); > + /* > + * Check if the handle is still associated with the event, > + * to handle cases where if the sink failed to start the > + * trace and TRUNCATED the handle already. > + */ > + if (READ_ONCE(handle->event)) { > + perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED); > + perf_aux_output_end(handle, 0); > + }
Makes sense as perf_aux_output_[flag|end]() helpers do not validate the 'handle' themselves.
> fail: > event->hw.state = PERF_HES_STOPPED; > goto out; > @@ -519,7 +526,21 @@ static void etm_event_stop(struct perf_event *event, int mode) > > size = sink_ops(sink)->update_buffer(sink, handle, > event_data->snk_config); > - perf_aux_output_end(handle, size); > + /* > + * Make sure the handle is still valid as the > + * sink could have closed it from an IRQ. > + * The sink driver must handle the race with > + * update_buffer() and IRQ. Thus either we > + * should get a valid handle and valid size > + * (which may be 0). > + * > + * But we should never get a non-zero size with > + * an invalid handle. > + */ > + if (READ_ONCE(handle->event)) > + perf_aux_output_end(handle, size); > + else > + WARN_ON(size);
Right.
> } > > /* Disabling the path make its elements available to other sessions */ >
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
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