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Subject[PATCH v2 2/8] coresight: tmc-etr: Add barrier after updating AUX ring buffer
Date
Since a memory barrier is required between AUX trace data store and
aux_head store, and the AUX trace data is filled with memcpy(), it's
sufficient to use smp_wmb() so can ensure the trace data is visible
prior to updating aux_head.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
drivers/hwtracing/coresight/coresight-tmc-etr.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index acdb59e0e661..713205db15a1 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1563,6 +1563,14 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
*/
if (etr_perf->snapshot)
handle->head += size;
+
+ /*
+ * It requires the ordering between the AUX trace data and aux_head
+ * store, below smp_wmb() ensures the AUX trace data is visible prior
+ * to updating aux_head.
+ */
+ smp_wmb();
+
out:
/*
* Don't set the TRUNCATED flag in snapshot mode because 1) the
--
2.25.1
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