perf thread: Allow tools to register a thread->priv destructor

So that when thread__delete() runs it can be called and free stuff tools
stashed into thread->priv, like 'perf trace' does and will use this
new facility to plug some leaks.

Added an assert(thread__priv_destructor == NULL) as suggested in Ian's
review.

Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/CAP-5=fV3Er=Ek8=iE=bSGbEBmM56_PJffMWot1g_5Bh8B5hO7A@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/thread.c

@@ -80,6 +80,15 @@ struct thread *thread__new(pid_t pid, pid_t tid)
 	return NULL;
 }
 
+static void (*thread__priv_destructor)(void *priv);
+
+void thread__set_priv_destructor(void (*destructor)(void *priv))
+{
+	assert(thread__priv_destructor == NULL);
+
+	thread__priv_destructor = destructor;
+}
+
 void thread__delete(struct thread *thread)
 {
 	struct namespaces *namespaces, *tmp_namespaces;
@@ -112,6 +121,10 @@ void thread__delete(struct thread *thread)
 	exit_rwsem(thread__namespaces_lock(thread));
 	exit_rwsem(thread__comm_lock(thread));
 	thread__free_stitch_list(thread);
+
+	if (thread__priv_destructor)
+		thread__priv_destructor(thread__priv(thread));
+
 	RC_CHK_FREE(thread);
 }
 

tools/perf/util/thread.h

@@ -71,6 +71,8 @@ struct thread *thread__new(pid_t pid, pid_t tid);
 int thread__init_maps(struct thread *thread, struct machine *machine);
 void thread__delete(struct thread *thread);
 
+void thread__set_priv_destructor(void (*destructor)(void *priv));
+
 struct thread *thread__get(struct thread *thread);
 void thread__put(struct thread *thread);