[PATCH v10 18/20] perf maps: Fix lock inversion in maps__load_first()

[Ian Rogers]

In maps__load_first(), take a reference to the first map and drop
maps__lock(maps) before calling map__load() to avoid a read-to-write
self-deadlock when loading kernel maps inserts extra trampoline maps.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/maps.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index f808df2fe77b..7ca33e5218e7 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -1459,10 +1459,15 @@ int maps__merge_in(struct maps *kmaps, struct map *new_map)
 
 void maps__load_first(struct maps *maps)
 {
-	down_read(maps__lock(maps));
+	struct map *first = NULL;
 
+	down_read(maps__lock(maps));
 	if (maps__nr_maps(maps) > 0)
-		map__load(maps__maps_by_address(maps)[0]);
-
+		first = map__get(maps__maps_by_address(maps)[0]);
 	up_read(maps__lock(maps));
+
+	if (first) {
+		map__load(first);
+		map__put(first);
+	}
 }
-- 
2.56.0.455.g6c5a503b38-goog