[PATCH 14/14] tracing: Switch trace_stat.c code over to use guard()

[Steven Rostedt <rostedt@goodmis.org>]

From: Steven Rostedt <rostedt@goodmis.org>

There are a couple functions in trace_stat.c that have "goto out" or
equivalent on error in order to release locks that were taken. This can be
error prone or just simply make the code more complex.

Switch every location that ends with unlocking a mutex on error over to
using the guard(mutex)() infrastructure to let the compiler worry about
releasing locks. This makes the code easier to read and understand.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_stat.c | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_stat.c b/kernel/trace/trace_stat.c
index bb247beec447..b3b5586f104d 100644
--- a/kernel/trace/trace_stat.c
+++ b/kernel/trace/trace_stat.c
@@ -128,7 +128,7 @@ static int stat_seq_init(struct stat_session *session)
 	int ret = 0;
 	int i;
 
-	mutex_lock(&session->stat_mutex);
+	guard(mutex)(&session->stat_mutex);
 	__reset_stat_session(session);
 
 	if (!ts->stat_cmp)
@@ -136,11 +136,11 @@ static int stat_seq_init(struct stat_session *session)
 
 	stat = ts->stat_start(ts);
 	if (!stat)
-		goto exit;
+		return 0;
 
 	ret = insert_stat(root, stat, ts->stat_cmp);
 	if (ret)
-		goto exit;
+		return ret;
 
 	/*
 	 * Iterate over the tracer stat entries and store them in an rbtree.
@@ -157,13 +157,10 @@ static int stat_seq_init(struct stat_session *session)
 			goto exit_free_rbtree;
 	}
 
-exit:
-	mutex_unlock(&session->stat_mutex);
 	return ret;
 
 exit_free_rbtree:
 	__reset_stat_session(session);
-	mutex_unlock(&session->stat_mutex);
 	return ret;
 }
 
@@ -308,7 +305,7 @@ static int init_stat_file(struct stat_session *session)
 int register_stat_tracer(struct tracer_stat *trace)
 {
 	struct stat_session *session, *node;
-	int ret = -EINVAL;
+	int ret;
 
 	if (!trace)
 		return -EINVAL;
@@ -316,18 +313,18 @@ int register_stat_tracer(struct tracer_stat *trace)
 	if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
 		return -EINVAL;
 
+	guard(mutex)(&all_stat_sessions_mutex);
+
 	/* Already registered? */
-	mutex_lock(&all_stat_sessions_mutex);
 	list_for_each_entry(node, &all_stat_sessions, session_list) {
 		if (node->ts == trace)
-			goto out;
+			return -EINVAL;
 	}
 
-	ret = -ENOMEM;
 	/* Init the session */
 	session = kzalloc(sizeof(*session), GFP_KERNEL);
 	if (!session)
-		goto out;
+		return -ENOMEM;
 
 	session->ts = trace;
 	INIT_LIST_HEAD(&session->session_list);
@@ -336,16 +333,13 @@ int register_stat_tracer(struct tracer_stat *trace)
 	ret = init_stat_file(session);
 	if (ret) {
 		destroy_session(session);
-		goto out;
+		return ret;
 	}
 
-	ret = 0;
 	/* Register */
 	list_add_tail(&session->session_list, &all_stat_sessions);
- out:
-	mutex_unlock(&all_stat_sessions_mutex);
 
-	return ret;
+	return 0;
 }
 
 void unregister_stat_tracer(struct tracer_stat *trace)
-- 
2.45.2