linux-kernel - [PATCH v1] PM: hibernate: Avoid redundant resume_device assignment in resume

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Message-Id: <20250530100036.11954-1-zhangzihuan@kylinos.cn>
Date: Fri, 30 May 2025 18:00:36 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: rafael@...nel.org,
	pavel@...nel.org,
	len.brown@...el.com
Cc: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zihuan Zhang <zhangzihuan@...inos.cn>
Subject: [PATCH v1] PM: hibernate: Avoid redundant resume_device assignment in resume_store()

In resume_store(), if the device number written to /sys/power/resume
is the same as the current swsusp_resume_device, we can skip reassignment.
This avoids unnecessary locking and improves efficiency slightly.

Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
---
 kernel/power/hibernate.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 519fb09de5e0..504a1c2465ce 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -1291,6 +1291,9 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
 	if (error)
 		return error;
 
+	if (dev == swsusp_resume_device)
+		return n;
+
 	sleep_flags = lock_system_sleep();
 	swsusp_resume_device = dev;
 	unlock_system_sleep(sleep_flags);
-- 
2.25.1