Commit f3bed55e authored Apr 17, 2020 by Ian Rogers Committed by Peter Zijlstra Apr 22, 2020

perf/core: fix parent pid/tid in task exit events



Current logic yields the child task as the parent.

Before:
$ perf record bash -c "perf list > /dev/null"
$ perf script -D |grep 'FORK\|EXIT'
4387036190981094 0x5a70 [0x30]: PERF_RECORD_FORK(10472:10472):(10470:10470)
4387036606207580 0xf050 [0x30]: PERF_RECORD_EXIT(10472:10472):(10472:10472)
4387036607103839 0x17150 [0x30]: PERF_RECORD_EXIT(10470:10470):(10470:10470)
                                                   ^
  Note the repeated values here -------------------/

After:
383281514043 0x9d8 [0x30]: PERF_RECORD_FORK(2268:2268):(2266:2266)
383442003996 0x2180 [0x30]: PERF_RECORD_EXIT(2268:2268):(2266:2266)
383451297778 0xb70 [0x30]: PERF_RECORD_EXIT(2266:2266):(2265:2265)

Fixes: 94d5d1b2 ("perf_counter: Report the cloning task as parent on perf_counter_fork()")
Reported-by: KP Singh <kpsingh@google.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200417182842.12522-1-irogers@google.com

parent 5b16ef2e

kernel/events/core.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -7491,10 +7491,17 @@ static void perf_event_task_output(struct perf_event *event,
		goto out;

		task_event->event_id.pid = perf_event_pid(event, task);
		task_event->event_id.ppid = perf_event_pid(event, current);

		task_event->event_id.tid = perf_event_tid(event, task);

		if (task_event->event_id.header.type == PERF_RECORD_EXIT) {
		task_event->event_id.ppid = perf_event_pid(event,
		task->real_parent);
		task_event->event_id.ptid = perf_event_pid(event,
		task->real_parent);
		} else { /* PERF_RECORD_FORK */
		task_event->event_id.ppid = perf_event_pid(event, current);
		task_event->event_id.ptid = perf_event_tid(event, current);
		}

		task_event->event_id.time = perf_event_clock(event);

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