linux-kernel - Re: [PATCH] coresight: tmc-etr: Fix perf

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Date:   Mon, 12 Aug 2019 11:45:29 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     yabinc@...gle.com, mathieu.poirier@...aro.org,
        alexander.shishkin@...ux.intel.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: tmc-etr: Fix perf_data check.



On 09/08/2019 21:23, Yabin Cui wrote:
> When tracing etm data of multiple threads on multiple cpus through
> perf interface, each cpu has a unique etr_perf_buffer while sharing
> the same etr device. There is no guarantee that the last cpu starts
> etm tracing also stops last. This makes perf_data check fail.
> 
> Fix it by checking etr_buf instead of etr_perf_buffer.

Please could you add a Fixes tag for this:

Fixes: 3147da92a8a81fc3 ("coresight: tmc-etr: Allocate and free ETR memory 
buffers for CPU-wide scenarios")

as the problem was introduced as a side effect of the above patch ?

> 
> Signed-off-by: Yabin Cui <yabinc@...gle.com>
> ---
>   drivers/hwtracing/coresight/coresight-tmc-etr.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 17006705287a..f466f05afe08 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -1484,7 +1484,7 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
>   		goto out;
>   	}
>   
> -	if (WARN_ON(drvdata->perf_data != etr_perf)) {
> +	if (WARN_ON(drvdata->perf_data != etr_buf)) {
>   		lost = true;
>   		spin_unlock_irqrestore(&drvdata->spinlock, flags);
>   		goto out;
> @@ -1556,7 +1556,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
>   	}
>   
>   	etr_perf->head = PERF_IDX2OFF(handle->head, etr_perf);
> -	drvdata->perf_data = etr_perf;
> +	drvdata->perf_data = etr_perf->etr_buf;

minor nit: Now that we are storing the etr_buf instead of the etr_perf_buf in
perf_data, we could make the "perf_data" => "perf_buf" inline with the
sysfs_buf.

Either ways:

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>