perf maps: Modify maps_by_name to hold a reference to a map

To make it clearer about the ownership of a reference count split the
by-name case from the regular start-address sorted tree. Put the
reference count when maps_by_name is freed, which requires moving a
decrement to nr_maps in maps__remove. Add two missing map puts in
maps__fixup_overlappings in the event maps__insert fails.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.g.garry@oracle.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Miaoqian Lin <linmq006@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Riccardo Mancini <rickyman7@gmail.com>
Cc: Shunsuke Nakamura <nakamura.shun@fujitsu.com>
Cc: Song Liu <song@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Yury Norov <yury.norov@gmail.com>
Link: https://lore.kernel.org/r/20230404205954.2245628-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/maps.c

@@ -26,6 +26,9 @@ static void __maps__free_maps_by_name(struct maps *maps)
 	/*
 	 * Free everything to try to do it from the rbtree in the next search
 	 */
+	for (unsigned int i = 0; i < maps__nr_maps(maps); i++)
+		map__put(maps__maps_by_name(maps)[i]);
+
 	zfree(&maps->maps_by_name);
 	maps->nr_maps_allocated = 0;
 }
@@ -42,7 +45,7 @@ static int __maps__insert(struct maps *maps, struct map *map)
 		return -ENOMEM;
 
 	RB_CLEAR_NODE(&new_rb_node->rb_node);
-	new_rb_node->map = map;
+	new_rb_node->map = map__get(map);
 
 	while (*p != NULL) {
 		parent = *p;
@@ -55,7 +58,6 @@ static int __maps__insert(struct maps *maps, struct map *map)
 
 	rb_link_node(&new_rb_node->rb_node, parent, p);
 	rb_insert_color(&new_rb_node->rb_node, maps__entries(maps));
-	map__get(map);
 	return 0;
 }
 
@@ -100,7 +102,7 @@ int maps__insert(struct maps *maps, struct map *map)
 			maps->maps_by_name = maps_by_name;
 			maps->nr_maps_allocated = nr_allocate;
 		}
-		maps__maps_by_name(maps)[maps__nr_maps(maps) - 1] = map;
+		maps__maps_by_name(maps)[maps__nr_maps(maps) - 1] = map__get(map);
 		__maps__sort_by_name(maps);
 	}
  out:
@@ -126,9 +128,9 @@ void maps__remove(struct maps *maps, struct map *map)
 	rb_node = maps__find_node(maps, map);
 	assert(rb_node->map == map);
 	__maps__remove(maps, rb_node);
-	--maps->nr_maps;
 	if (maps__maps_by_name(maps))
 		__maps__free_maps_by_name(maps);
+	--maps->nr_maps;
 	up_write(maps__lock(maps));
 }
 
@@ -136,6 +138,9 @@ static void __maps__purge(struct maps *maps)
 {
 	struct map_rb_node *pos, *next;
 
+	if (maps__maps_by_name(maps))
+		__maps__free_maps_by_name(maps);
+
 	maps__for_each_entry_safe(maps, pos, next) {
 		rb_erase_init(&pos->rb_node,  maps__entries(maps));
 		map__put(pos->map);
@@ -293,7 +298,7 @@ int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp)
 	}
 
 	next = first;
-	while (next) {
+	while (next && !err) {
 		struct map_rb_node *pos = rb_entry(next, struct map_rb_node, rb_node);
 		next = rb_next(&pos->rb_node);
 
@@ -331,8 +336,10 @@ int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp)
 
 			before->end = map__start(map);
 			err = __maps__insert(maps, before);
-			if (err)
+			if (err) {
+				map__put(before);
 				goto put_map;
+			}
 
 			if (verbose >= 2 && !use_browser)
 				map__fprintf(before, fp);
@@ -352,22 +359,17 @@ int maps__fixup_overlappings(struct maps *maps, struct map *map, FILE *fp)
 			assert(map__map_ip(pos->map, map__end(map)) ==
 				map__map_ip(after, map__end(map)));
 			err = __maps__insert(maps, after);
-			if (err)
+			if (err) {
+				map__put(after);
 				goto put_map;
-
+			}
 			if (verbose >= 2 && !use_browser)
 				map__fprintf(after, fp);
 			map__put(after);
 		}
 put_map:
 		map__put(pos->map);
-
-		if (err)
-			goto out;
 	}
-
-	err = 0;
-out:
 	up_write(maps__lock(maps));
 	return err;
 }

tools/perf/util/symbol.c

@@ -2053,10 +2053,23 @@ int dso__load(struct dso *dso, struct map *map)
 
 static int map__strcmp(const void *a, const void *b)
 {
-	const struct dso *dso_a = map__dso(*(const struct map **)a);
-	const struct dso *dso_b = map__dso(*(const struct map **)b);
+	const struct map *map_a = *(const struct map **)a;
+	const struct map *map_b = *(const struct map **)b;
+	const struct dso *dso_a = map__dso(map_a);
+	const struct dso *dso_b = map__dso(map_b);
+	int ret = strcmp(dso_a->short_name, dso_b->short_name);
 
-	return strcmp(dso_a->short_name, dso_b->short_name);
+	if (ret == 0 && map_a != map_b) {
+		/*
+		 * Ensure distinct but name equal maps have an order in part to
+		 * aid reference counting.
+		 */
+		ret = (int)map__start(map_a) - (int)map__start(map_b);
+		if (ret == 0)
+			ret = (int)((intptr_t)map_a - (intptr_t)map_b);
+	}
+
+	return ret;
 }
 
 static int map__strcmp_name(const void *name, const void *b)
@@ -2088,7 +2101,7 @@ static int map__groups__sort_by_name_from_rbtree(struct maps *maps)
 	maps->nr_maps_allocated = maps__nr_maps(maps);
 
 	maps__for_each_entry(maps, rb_node)
-		maps_by_name[i++] = rb_node->map;
+		maps_by_name[i++] = map__get(rb_node->map);
 
 	__maps__sort_by_name(maps);