coresight: perf: Retrieve path and source from event data

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ETM perf callbacks currently use the per-CPU csdev_src pointer, which
can race with updates during device registration and unregistration.

The AUX setup already builds and stores the path in the event data.
Use this path to retrieve the source instead of csdev_src to avoid
the race.

Export coresight_get_source() and add etm_event_get_ctxt_path() to
retrieve the context's path and its source with READ_ONCE() /
WRITE_ONCE() accessors. Give the comments to explain why this
approach is safe when pause or resume callbacks preempt the disable
callback (e.g. via NMI).

Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Tested-by: James Clark <james.clark@linaro.org>
Tested-by: Jie Gan <jie.gan@oss.qualcomm.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20260515-arm_coresight_path_power_management_improvement-v14-7-f88c4a3ecfe9@arm.com

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Leo Yan 2026-05-15 21:08:14 +01:00 • committed by Suzuki K Poulose

parent 2c7f786928

commit f37bc31447

3 changed files with 74 additions and 43 deletions

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2

drivers/hwtracing/coresight/coresight-core.c

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116

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

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1

drivers/hwtracing/coresight/coresight-priv.h

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