linux-kernel - [PATCH] tracepoint: Optimize the critical region of mutex_lock in tracepoint_module

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Date:   Wed, 14 Sep 2022 14:14:16 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Steven Rostedt <rostedt@...dmis.org>,
        <linux-kernel@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH] tracepoint: Optimize the critical region of mutex_lock in tracepoint_module_coming()

The memory allocation of 'tp_mod' does not require mutex_lock()
protection, move it out.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 kernel/tracepoint.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index ef42c1a1192053c..f23144af5743048 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -640,7 +640,6 @@ static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
 static int tracepoint_module_coming(struct module *mod)
 {
 	struct tp_module *tp_mod;
-	int ret = 0;
 
 	if (!mod->num_tracepoints)
 		return 0;
@@ -652,19 +651,18 @@ static int tracepoint_module_coming(struct module *mod)
 	 */
 	if (trace_module_has_bad_taint(mod))
 		return 0;
-	mutex_lock(&tracepoint_module_list_mutex);
+
 	tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
-	if (!tp_mod) {
-		ret = -ENOMEM;
-		goto end;
-	}
+	if (!tp_mod)
+		return -ENOMEM;
 	tp_mod->mod = mod;
+
+	mutex_lock(&tracepoint_module_list_mutex);
 	list_add_tail(&tp_mod->list, &tracepoint_module_list);
 	blocking_notifier_call_chain(&tracepoint_notify_list,
 			MODULE_STATE_COMING, tp_mod);
-end:
 	mutex_unlock(&tracepoint_module_list_mutex);
-	return ret;
+	return 0;
 }
 
 static void tracepoint_module_going(struct module *mod)
-- 
2.25.1