perf thread: Fix reference count initial state

We should always return from thread__new(), the constructor, with the
object with a reference count of one, so that:

     struct thread *thread = thread__new();
     thread__put(thread);

Will call thread__delete().

If any reference is made to that 'thread' variable, it better use
thread__get(thread) to hold a reference.

We were returning with thread->refcnt set to zero, fix it and some cases
where thread__delete() was being called, which were not a problem
because just one reference was being used, now that we set it to 1, use
thread__put() instead.

Reported-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-4b9mkuk66to4ecckpmpvqx6s@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 0a9ae80..dfd00c6 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -19,8 +19,10 @@ int thread__init_map_groups(struct thread *thread, struct machine *machine)
 		thread->mg = map_groups__new(machine);
 	} else {
 		leader = __machine__findnew_thread(machine, pid, pid);
-		if (leader)
+		if (leader) {
 			thread->mg = map_groups__get(leader->mg);
+			thread__put(leader);
+		}
 	}
 
 	return thread->mg ? 0 : -1;
@@ -53,7 +55,7 @@ struct thread *thread__new(pid_t pid, pid_t tid)
 			goto err_thread;
 
 		list_add(&comm->list, &thread->comm_list);
-		atomic_set(&thread->refcnt, 0);
+		atomic_set(&thread->refcnt, 1);
 		RB_CLEAR_NODE(&thread->rb_node);
 	}
 
@@ -95,6 +97,10 @@ struct thread *thread__get(struct thread *thread)
 void thread__put(struct thread *thread)
 {
 	if (thread && atomic_dec_and_test(&thread->refcnt)) {
+		/*
+		 * Remove it from the dead_threads list, as last reference
+		 * is gone.
+		 */
 		list_del_init(&thread->node);
 		thread__delete(thread);
 	}