Messages in this thread |  | | Date | Fri, 1 Sep 2017 09:21:33 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH 03/10] perf: Make sure we read only scheduled events |
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On Mon, Aug 28, 2017 at 09:23:59PM +0200, Peter Zijlstra wrote: > On Thu, Aug 24, 2017 at 06:27:30PM +0200, Jiri Olsa wrote: > > Adding leader's state check into perf_output_read_group > > to ensure we read only leader, which is scheduled in. > > > > Similar check is already there for siblings. > > > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > --- > > kernel/events/core.c | 10 +++++++--- > > 1 file changed, 7 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index 30e30e94ea32..9a2791afe051 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -5760,6 +5760,11 @@ void perf_event__output_id_sample(struct perf_event *event, > > __perf_event__output_id_sample(handle, sample); > > } > > > > +static bool can_read(struct perf_event *event) > > +{ > > + return event->state == PERF_EVENT_STATE_ACTIVE; > > +} > > + > > static void perf_output_read_one(struct perf_output_handle *handle, > > struct perf_event *event, > > u64 enabled, u64 running) > > @@ -5800,7 +5805,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, > > if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) > > values[n++] = running; > > > > - if (leader != event) > > + if ((leader != event) && can_read(leader)) > > leader->pmu->read(leader); > > > > values[n++] = perf_event_count(leader); > > @@ -5812,8 +5817,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, > > list_for_each_entry(sub, &leader->sibling_list, group_entry) { > > n = 0; > > > > - if ((sub != event) && > > - (sub->state == PERF_EVENT_STATE_ACTIVE)) > > + if ((sub != event) && can_read(sub)) > > sub->pmu->read(sub); > > > > values[n++] = perf_event_count(sub); > > I'm not seeing how this makes sense. Groups should either _all_ be > scheduled or not at all. Please explain.
so this could be called for event which is already scheduled out:
perf_event_exit_task_context task_ctx_sched_out <- unschedules event perf_event_exit_event sync_child_event perf_event_read_event perf_output_read
if leader != events (which is, if you don't have Mark's fix), we'll call leader->pmu->read(leader) even if it's not scheduled in
jirka
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