linux-kernel - [for-next][PATCH 09/20] tracepoint: Optimize the critical region of mutex_lock in tracepoint_module

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Message-ID: <20220927160245.524291097@goodmis.org>
Date:   Tue, 27 Sep 2022 12:02:25 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        Zhen Lei <thunder.leizhen@...wei.com>
Subject: [for-next][PATCH 09/20] tracepoint: Optimize the critical region of mutex_lock in
 tracepoint_module_coming()

From: Zhen Lei <thunder.leizhen@...wei.com>

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

Link: https://lkml.kernel.org/r/20220914061416.1630-1-thunder.leizhen@huawei.com

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

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index ef42c1a11920..f23144af5743 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)
-- 
2.35.1