[PATCH v1] perf cs-etm: Pass -1 as pid value for machine__set_current_tid()
From: Leo Yan <hidden>
Date: 2021-11-13 14:35:56
Also in:
linux-perf-users, lkml
Subsystem:
arm/coresight framework and drivers, performance events subsystem, performance events tooling arm64, the rest · Maintainers:
Suzuki K Poulose, Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo, Namhyung Kim, Linus Torvalds
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 <redacted> --- 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); if (err) return err;
--
2.25.1
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