linux-kernel - [PATCH] release_task: kill the no longer needed get/put_pid(thread

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Message-ID: <20250411121857.GA10550@redhat.com>
Date: Fri, 11 Apr 2025 14:18:57 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Christian Brauner <brauner@...nel.org>,
	Mateusz Guzik <mjguzik@...il.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] release_task: kill the no longer needed
 get/put_pid(thread_pid)

After the commit 7903f907a2260 ("pid: perform free_pid() calls outside
of tasklist_lock") __unhash_process() -> detach_pid() no longer calls
free_pid(), proc_flush_pid() can just use p->thread_pid without the
now pointless get_pid() + put_pid().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/exit.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 1b51dc099f1e..96d639383f86 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -239,7 +239,6 @@ void release_task(struct task_struct *p)
 {
 	struct release_task_post post;
 	struct task_struct *leader;
-	struct pid *thread_pid;
 	int zap_leader;
 repeat:
 	memset(&post, 0, sizeof(post));
@@ -253,8 +252,6 @@ void release_task(struct task_struct *p)
 	pidfs_exit(p);
 	cgroup_release(p);
 
-	thread_pid = get_pid(p->thread_pid);
-
 	write_lock_irq(&tasklist_lock);
 	ptrace_release_task(p);
 	__exit_signal(&post, p);
@@ -282,8 +279,8 @@ void release_task(struct task_struct *p)
 	}
 
 	write_unlock_irq(&tasklist_lock);
-	proc_flush_pid(thread_pid);
-	put_pid(thread_pid);
+	/* p->thread_pid can't go away until free_pids() below */
+	proc_flush_pid(p->thread_pid);
 	add_device_randomness(&p->se.sum_exec_runtime,
 			      sizeof(p->se.sum_exec_runtime));
 	free_pids(post.pids);
-- 
2.25.1.362.g51ebf55