linux-kernel - [PATCH 03/10] perf: Make sure we read only scheduled events

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Date:   Thu, 24 Aug 2017 18:27:30 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Andi Kleen <andi@...stfloor.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 03/10] perf: Make sure we read only scheduled events

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@...nel.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);
-- 
2.9.5