Messages in this thread | | | Date | Fri, 19 Nov 2021 08:33:17 +0800 | From | Leo Yan <> | Subject | Re: [PATCH v1] perf cs-etm: Pass -1 as pid value for machine__set_current_tid() |
| |
Hi Mathieu,
On Thu, Nov 18, 2021 at 10:14:12AM -0700, Mathieu Poirier wrote: > 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 tried to capture log but I didn't observe the difference introduced by this patch, this might because I didn't per-process mode for multi-threading case. I will try more case for this.
> 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.
Will do. And will Cc James and German in next spin.
Thanks for review and suggestion.
Leo
| |