linux-kernel - [PATCH] kernel/fork: Optimize by avoiding unnecessary locking for kernel threads

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Message-Id: <20241202091055.49551-1-zhen.ni@easystack.cn>
Date: Mon,  2 Dec 2024 17:10:55 +0800
From: Zhen Ni <zhen.ni@...ystack.cn>
To: akpm@...ux-foundation.org,
	brauner@...nel.org,
	oleg@...hat.com,
	tglx@...utronix.de,
	frederic@...nel.org,
	richard.weiyang@...il.com,
	zhangpeng.00@...edance.com
Cc: linux-kernel@...r.kernel.org,
	Zhen Ni <zhen.ni@...ystack.cn>
Subject: [PATCH] kernel/fork: Optimize by avoiding unnecessary locking for kernel threads

Improves the function by checking if the task is a kernel thread
(PF_KTHREAD) before acquiring the task lock. Kernel threads do not
have an associated executable file, so the function now returns NULL
immediately in such cases. This change reduces unnecessary locking
overhead and simplifies the code logic, while maintaining consistent
behavior for regular tasks.

Signed-off-by: Zhen Ni <zhen.ni@...ystack.cn>
---
 kernel/fork.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index e58d27c05788..9fadde6c7c98 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1500,12 +1500,13 @@ struct file *get_task_exe_file(struct task_struct *task)
 	struct file *exe_file = NULL;
 	struct mm_struct *mm;
 
+	if (task->flags & PF_KTHREAD)
+		return NULL;
+
 	task_lock(task);
 	mm = task->mm;
-	if (mm) {
-		if (!(task->flags & PF_KTHREAD))
-			exe_file = get_mm_exe_file(mm);
-	}
+	if (mm)
+		exe_file = get_mm_exe_file(mm);
 	task_unlock(task);
 	return exe_file;
 }
-- 
2.20.1