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| author | Leo Yan <leo.yan@linaro.org> | 2021-08-09 13:14:01 +0200 |
|---|---|---|
| committer | Mathieu Poirier <mathieu.poirier@linaro.org> | 2021-10-27 19:44:43 +0200 |
| commit | bd8d06886d0a9b59d020fdb2496c76db77816768 (patch) | |
| tree | 9ab9cd257deee2d018734e0cc29c654b387ef9f4 | |
| parent | coresight: tmc-etr: Add barrier after updating AUX ring buffer (diff) | |
| download | linux-bd8d06886d0a9b59d020fdb2496c76db77816768.tar.xz linux-bd8d06886d0a9b59d020fdb2496c76db77816768.zip | |
coresight: tmc-etf: Add comment for store ordering
Since the function CS_LOCK() has contained memory barrier mb(), it
ensures the visibility of the AUX trace data before updating the
aux_head, thus it's needless to add any explicit barrier anymore.
Add comment to make clear for the barrier usage for ETF.
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lore.kernel.org/r/20210809111407.596077-4-leo.yan@linaro.org
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
| -rw-r--r-- | drivers/hwtracing/coresight/coresight-tmc-etf.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index cd0fb7bfba68..8debd4f40f06 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -553,6 +553,11 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev, if (buf->snapshot) handle->head += to_read; + /* + * CS_LOCK() contains mb() so it can ensure visibility of the AUX trace + * data before the aux_head is updated via perf_aux_output_end(), which + * is expected by the perf ring buffer. + */ CS_LOCK(drvdata->base); out: spin_unlock_irqrestore(&drvdata->spinlock, flags); |