diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 5c26e2d..e437edb 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -12,6 +12,7 @@
 #include "event.h"
 #include "symbol.h"
 #include <linux/kernel.h>
+#include "debug.h"
 
 static int build_id__mark_dso_hit(event_t *event, struct perf_session *session)
 {
@@ -34,10 +35,27 @@
 	return 0;
 }
 
+static int event__exit_del_thread(event_t *self, struct perf_session *session)
+{
+	struct thread *thread = perf_session__findnew(session, self->fork.tid);
+
+	dump_printf("(%d:%d):(%d:%d)\n", self->fork.pid, self->fork.tid,
+		    self->fork.ppid, self->fork.ptid);
+
+	if (thread) {
+		rb_erase(&thread->rb_node, &session->threads);
+		session->last_match = NULL;
+		thread__delete(thread);
+	}
+
+	return 0;
+}
+
 struct perf_event_ops build_id__mark_dso_hit_ops = {
 	.sample	= build_id__mark_dso_hit,
 	.mmap	= event__process_mmap,
 	.fork	= event__process_task,
+	.exit	= event__exit_del_thread,
 };
 
 char *dso__build_id_filename(struct dso *self, char *bf, size_t size)
diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 37cab90..2ddbae3 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -228,6 +228,39 @@
 	self->machine = NULL;
 }
 
+static void maps__delete(struct rb_root *self)
+{
+	struct rb_node *next = rb_first(self);
+
+	while (next) {
+		struct map *pos = rb_entry(next, struct map, rb_node);
+
+		next = rb_next(&pos->rb_node);
+		rb_erase(&pos->rb_node, self);
+		map__delete(pos);
+	}
+}
+
+static void maps__delete_removed(struct list_head *self)
+{
+	struct map *pos, *n;
+
+	list_for_each_entry_safe(pos, n, self, node) {
+		list_del(&pos->node);
+		map__delete(pos);
+	}
+}
+
+void map_groups__exit(struct map_groups *self)
+{
+	int i;
+
+	for (i = 0; i < MAP__NR_TYPES; ++i) {
+		maps__delete(&self->maps[i]);
+		maps__delete_removed(&self->removed_maps[i]);
+	}
+}
+
 void map_groups__flush(struct map_groups *self)
 {
 	int type;
diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
index 3b2f706..20eba42 100644
--- a/tools/perf/util/map.h
+++ b/tools/perf/util/map.h
@@ -127,6 +127,7 @@
 void maps__insert(struct rb_root *maps, struct map *map);
 struct map *maps__find(struct rb_root *maps, u64 addr);
 void map_groups__init(struct map_groups *self);
+void map_groups__exit(struct map_groups *self);
 int map_groups__clone(struct map_groups *self,
 		      struct map_groups *parent, enum map_type type);
 size_t map_groups__fprintf(struct map_groups *self, int verbose, FILE *fp);
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 9a448b4..8c72d88 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -62,6 +62,13 @@
 	return self;
 }
 
+void thread__delete(struct thread *self)
+{
+	map_groups__exit(&self->mg);
+	free(self->comm);
+	free(self);
+}
+
 int thread__set_comm(struct thread *self, const char *comm)
 {
 	int err;
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index ee6bbcf..688500f 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -20,6 +20,8 @@
 
 struct perf_session;
 
+void thread__delete(struct thread *self);
+
 int find_all_tid(int pid, pid_t ** all_tid);
 int thread__set_comm(struct thread *self, const char *comm);
 int thread__comm_len(struct thread *self);