linux-kernel - [PATCH AUTOSEL 4.19 26/30] perf/core: fix parent pid/tid in task exit events

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Date:   Thu, 30 Apr 2020 09:53:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ian Rogers <irogers@...gle.com>, KP Singh <kpsingh@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 26/30] perf/core: fix parent pid/tid in task exit events

From: Ian Rogers <irogers@...gle.com>

[ Upstream commit f3bed55e850926614b9898fe982f66d2541a36a5 ]

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: 94d5d1b2d891 ("perf_counter: Report the cloning task as parent on perf_counter_fork()")
Reported-by: KP Singh <kpsingh@...gle.com>
Signed-off-by: Ian Rogers <irogers@...gle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20200417182842.12522-1-irogers@google.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/events/core.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 00fb2fe92c4d6..21e3c65abc76f 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6923,10 +6923,17 @@ 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);
-	task_event->event_id.ptid = perf_event_tid(event, current);
+
+	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);
 
-- 
2.20.1