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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: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mathieu Poirier 2019-06-19 11:29:09 -06:00 committed by Greg Kroah-Hartman
parent 99f81eb9c5
commit 5aafd9bf7a
3 changed files with 21 additions and 3 deletions
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8
drivers/hwtracing/coresight/coresight-etb10.c
View File

@ -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 */

8
drivers/hwtracing/coresight/coresight-tmc-etf.c
View File

@ -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;

8
drivers/hwtracing/coresight/coresight-tmc-etr.c
View File

@ -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;
}