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, 12 insertions, 7 deletions

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 1407d5107480..ad79297c76c8 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -352,13 +352,18 @@ static void machine__update_thread_pid(struct machine *machine,
 	}
 
 	th->mg = map_groups__get(leader->mg);
-
+out_put:
+	thread__put(leader);
 	return;
-
 out_err:
 	pr_err("Failed to join map groups for %d:%d\n", th->pid_, th->tid);
+	goto out_put;
 }
 
+/*
+ * Caller must eventually drop thread->refcnt returned with a successfull
+ * lookup/new thread inserted.
+ */
 static struct thread *____machine__findnew_thread(struct machine *machine,
 						  pid_t pid, pid_t tid,
 						  bool create)
@@ -376,7 +381,7 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 	if (th != NULL) {
 		if (th->tid == tid) {
 			machine__update_thread_pid(machine, th, pid);
-			return th;
+			return thread__get(th);
 		}
 
 		machine->last_match = NULL;
@@ -389,7 +394,7 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 		if (th->tid == tid) {
 			machine->last_match = th;
 			machine__update_thread_pid(machine, th, pid);
-			return th;
+			return thread__get(th);
 		}
 
 		if (tid < th->tid)
@@ -417,7 +422,7 @@ static struct thread *____machine__findnew_thread(struct machine *machine,
 		if (thread__init_map_groups(th, machine)) {
 			rb_erase_init(&th->rb_node, &machine->threads);
 			RB_CLEAR_NODE(&th->rb_node);
-			thread__delete(th);
+			thread__put(th);
 			return NULL;
 		}
 		/*
@@ -441,7 +446,7 @@ struct thread *machine__findnew_thread(struct machine *machine, pid_t pid,
 	struct thread *th;
 
 	pthread_rwlock_wrlock(&machine->threads_lock);
-	th = thread__get(__machine__findnew_thread(machine, pid, tid));
+	th = __machine__findnew_thread(machine, pid, tid);
 	pthread_rwlock_unlock(&machine->threads_lock);
 	return th;
 }
@@ -451,7 +456,7 @@ struct thread *machine__find_thread(struct machine *machine, pid_t pid,
 {
 	struct thread *th;
 	pthread_rwlock_rdlock(&machine->threads_lock);
-	th =  thread__get(____machine__findnew_thread(machine, pid, tid, false));
+	th =  ____machine__findnew_thread(machine, pid, tid, false);
 	pthread_rwlock_unlock(&machine->threads_lock);
 	return th;
 }