[PATCH 1/4] libperf evlist: Update group info in perf_evlist__remove()

[Namhyung Kim <namhyung@kernel.org>]

When an event in a group is removed, it should update the group status
including the pointer to leader and number of member events.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/lib/perf/evlist.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
index 058e3ff10f9b..befdb062fa1d 100644
--- a/tools/lib/perf/evlist.c
+++ b/tools/lib/perf/evlist.c
@@ -102,8 +102,29 @@ void perf_evlist__add(struct perf_evlist *evlist,
 void perf_evlist__remove(struct perf_evlist *evlist,
 			 struct perf_evsel *evsel)
 {
+	struct perf_evsel *leader = evsel->leader;
+
 	list_del_init(&evsel->node);
 	evlist->nr_entries -= 1;
+
+	/* return stand-alone event */
+	if (leader == evsel && leader->nr_members < 2)
+		return;
+
+	if (leader == evsel) {
+		struct perf_evsel *member;
+
+		/* select the next event as a new leader */
+		leader = member = perf_evlist__next(evlist, evsel);
+
+		/* update members to see the new leader */
+		while (member && member->leader == evsel) {
+			member->leader = leader;
+			member = perf_evlist__next(evlist, member);
+		}
+	}
+
+	leader->nr_members = evsel->leader->nr_members - 1;
 }
 
 struct perf_evlist *perf_evlist__new(void)
-- 
2.43.0.687.g38aa6559b0-goog