Commit 2ef43054 authored by Suzuki K Poulose's avatar Suzuki K Poulose Committed by Mathieu Poirier
Browse files

coresight: etm-pmu: Ensure the AUX handle is valid 



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>
Reviewed-by: default avatarAnshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210914102641.1852544-4-suzuki.poulose@arm.com


Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
parent 5f6fd1aa

drivers/hwtracing/coresight/coresight-etm-perf.c

+24 −3
Original line number Diff line number Diff line
@@ -485,8 +485,15 @@ static void etm_event_start(struct perf_event *event, int flags) 
fail_disable_path:

	coresight_disable_path(path);

fail_end_stop:

	/*

	 * 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);

	}

fail:

	event->hw.state = PERF_HES_STOPPED;

	return;
@@ -567,7 +574,21 @@ static void etm_event_stop(struct perf_event *event, int mode) 


		size = sink_ops(sink)->update_buffer(sink, handle,

					      event_data->snk_config);

		/*

		 * 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);

	}



	/* Disabling the path make its elements available to other sessions */