Good morning Leo,
On Sat, Nov 13, 2021 at 10:35:40PM +0800, Leo Yan wrote:
Currently, cs-etm passes the tid value for both tid and pid parameters when calling machine__set_current_tid(), this can lead to confusion for thread handling. E.g. we arbitrarily pass the same value for pid and tid, perf tool will be misled to consider it is a main thread (see thread__main_thread()).
On the other hand, Perf tool only can retrieve tid from Arm CoreSight context packet, and we have no chance to know pid (it maps to kernel's task_struct::tgid) from hardware tracing data. For this reason, this patch passes -1 as pid for function machine__set_current_tid().
Signed-off-by: Leo Yan leo.yan@linaro.org
tools/perf/util/cs-etm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index f323adb1af85..eed1a5930072 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1118,7 +1118,7 @@ int cs_etm__etmq_set_tid(struct cs_etm_queue *etmq, if (cs_etm__get_cpu(trace_chan_id, &cpu) < 0) return err;
- err = machine__set_current_tid(etm->machine, cpu, tid, tid);
- err = machine__set_current_tid(etm->machine, cpu, -1, tid);
I remember wondering about what to do with the pid parameter when I wrote this patch...
Do you have a before-and-after snapshot you can add to the changelog? I also think it will require a "Fixes" tag. In your next revision please CC James since you guys are working in that area nowadays.
Thanks, Mathieu
if (err) return err; -- 2.25.1