Re: [PATCH v5 2/9] coresight: tmc-etr: Add barrier after updating AUX ring buffer

[Leo Yan]

Hi Mathieu, Suzuki,

On Mon, Aug 09, 2021 at 07:14:00PM +0800, Leo Yan wrote:
> 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@xxxxxxxxxx>
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>

Could you pick up patches 02 and 03 in this series?  Please note,
patch 02 has the review tag from Suzuki, but I didn't receive the
review tag for patch 03.

If anything need to follow up, just let me know.  Thanks!

> ---
>  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..13fd1fc730ed 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;
> +
> +	/*
> +	 * Ensure that the AUX trace data is visible before the aux_head
> +	 * is updated via perf_aux_output_end(), as expected by the
> +	 * perf ring buffer.
> +	 */
> +	smp_wmb();
> +
>  out:
>  	/*
>  	 * Don't set the TRUNCATED flag in snapshot mode because 1) the
> -- 
> 2.25.1
>