perf tools: Reference count struct map

We have pointers to struct map instances in several places, like in the
hist_entry instances, so we need a way to know when we can destroy them,
otherwise we may either keep leaking them or end up referencing deleted
instances.

Start fixing it by reference counting them.

This patch puts the reference count for struct map in place, replacing
direct map__delete() calls with map__put() ones and then grabbing a
reference count when adding it to the maps struct where maps for a
struct thread are kept.

Next we'll grab reference counts when setting pointers to struct map
instances, in places like in the hist_entry code.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-wi19xczk0t2a41r1i2chuio5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/map.c

@@ -139,6 +139,7 @@ void map__init(struct map *map, enum map_type type,
 	map->groups   = NULL;
 	map->referenced = false;
 	map->erange_warned = false;
+	atomic_set(&map->refcnt, 1);
 }
 
 struct map *map__new(struct machine *machine, u64 start, u64 len,
@@ -229,6 +230,12 @@ void map__delete(struct map *map)
 	free(map);
 }
 
+void map__put(struct map *map)
+{
+	if (map && atomic_dec_and_test(&map->refcnt))
+		map__delete(map);
+}
+
 void map__fixup_start(struct map *map)
 {
 	struct rb_root *symbols = &map->dso->symbols[map->type];
@@ -448,7 +455,7 @@ static void __maps__purge(struct maps *maps)
 
 		next = rb_next(&pos->rb_node);
 		rb_erase_init(&pos->rb_node, root);
-		map__delete(pos);
+		map__put(pos);
 	}
 }
 
@@ -458,7 +465,7 @@ static void __maps__purge_removed_maps(struct maps *maps)
 
 	list_for_each_entry_safe(pos, n, &maps->removed_maps, node) {
 		list_del_init(&pos->node);
-		map__delete(pos);
+		map__put(pos);
 	}
 }
 
@@ -682,7 +689,7 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
 
 			if (before == NULL) {
 				err = -ENOMEM;
-				goto move_map;
+				goto put_map;
 			}
 
 			before->end = map->start;
@@ -696,7 +703,7 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
 
 			if (after == NULL) {
 				err = -ENOMEM;
-				goto move_map;
+				goto put_map;
 			}
 
 			after->start = map->end;
@@ -704,14 +711,14 @@ static int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp
 			if (verbose >= 2)
 				map__fprintf(after, fp);
 		}
-move_map:
+put_map:
 		/*
 		 * If we have references, just move them to a separate list.
 		 */
 		if (pos->referenced)
 			list_add_tail(&pos->node, &maps->removed_maps);
 		else
-			map__delete(pos);
+			map__put(pos);
 
 		if (err)
 			goto out;
@@ -772,6 +779,7 @@ static void __maps__insert(struct maps *maps, struct map *map)
 
 	rb_link_node(&map->rb_node, parent, p);
 	rb_insert_color(&map->rb_node, &maps->entries);
+	map__get(map);
 }
 
 void maps__insert(struct maps *maps, struct map *map)
@@ -784,6 +792,7 @@ void maps__insert(struct maps *maps, struct map *map)
 static void __maps__remove(struct maps *maps, struct map *map)
 {
 	rb_erase_init(&map->rb_node, &maps->entries);
+	map__put(map);
 }
 
 void maps__remove(struct maps *maps, struct map *map)