[PATCH v5 11/17] perf maps: Modify maps_by_name to hold a reference to a map

Ian Rogers
2023-03-20T21:25:28Z

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>
---
tools/perf/util/maps.c | 30 ++++++++++++++++--------------
tools/perf/util/symbol.c | 21 +++++++++++++++++----
2 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index ffd4a4a64026..74e3133f5007 100644
--- a/tools/perf/util/maps.c
+++ b/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;
}
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index ec7a312e7cc1..7904bfff7d0e 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2052,10 +2052,23 @@ 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)
@@ -2087,7 +2100,7 @@ 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);

--
2.40.0.rc1.284.g88254d51c5-goog