Commit 5aafd9bf authored by Mathieu Poirier's avatar Mathieu Poirier Committed by Greg Kroah-Hartman
Browse files

coresight: perf: Don't set the truncated flag in snapshot mode 



This patch avoids setting the truncated flag when operating in snapshot
mode since the trace buffer is expected to be truncated and discontinuous
from one snapshot to another.  Moreover when the truncated flag is set
the perf core stops enabling the event, waiting for user space to consume
the data.  In snapshot mode this is clearly not what we want since it
results in stale data.

Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: default avatarLeo Yan <leo.yan@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 99f81eb9

drivers/hwtracing/coresight/coresight-etb10.c

+7 −1
Original line number Diff line number Diff line
@@ -512,7 +512,13 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev, 
		lost = true;

	}



	if (lost)

	/*

	 * Don't set the TRUNCATED flag in snapshot mode because 1) the

	 * captured buffer is expected to be truncated and 2) a full buffer

	 * prevents the event from being re-enabled by the perf core,

	 * resulting in stale data being send to user space.

	 */

	if (!buf->snapshot && lost)

		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);



	/* finally tell HW where we want to start reading from */

drivers/hwtracing/coresight/coresight-tmc-etf.c

+7 −1
Original line number Diff line number Diff line
@@ -518,7 +518,13 @@ static unsigned long tmc_update_etf_buffer(struct coresight_device *csdev, 
		lost = true;

	}



	if (lost)

	/*

	 * Don't set the TRUNCATED flag in snapshot mode because 1) the

	 * captured buffer is expected to be truncated and 2) a full buffer

	 * prevents the event from being re-enabled by the perf core,

	 * resulting in stale data being send to user space.

	 */

	if (!buf->snapshot && lost)

		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);



	cur = buf->cur;

drivers/hwtracing/coresight/coresight-tmc-etr.c

+7 −1
Original line number Diff line number Diff line
@@ -1511,7 +1511,13 @@ tmc_update_etr_buffer(struct coresight_device *csdev, 


	lost |= etr_buf->full;

out:

	if (lost)

	/*

	 * Don't set the TRUNCATED flag in snapshot mode because 1) the

	 * captured buffer is expected to be truncated and 2) a full buffer

	 * prevents the event from being re-enabled by the perf core,

	 * resulting in stale data being send to user space.

	 */

	if (!etr_perf->snapshot && lost)

		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);

	return size;

}

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