[PATCH] release_task: kill the no longer needed get/put_pid(thread_pid)

[Oleg Nesterov]

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@xxxxxxxxxx>
Link: https://lore.kernel.org/20250411121857.GA10550@xxxxxxxxxx
Reviewed-by: Mateusz Guzik <mjguzik@xxxxxxxxx>
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
 kernel/exit.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index abcd93ce4e18..c33ecde016de 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -258,7 +258,8 @@ void release_task(struct task_struct *p)
 	pidfs_exit(p);
 	cgroup_release(p);
 
-	thread_pid = get_pid(p->thread_pid);
+	/* Retrieve @thread_pid before __unhash_process() may set it to NULL. */
+	thread_pid = task_pid(p);
 
 	write_lock_irq(&tasklist_lock);
 	ptrace_release_task(p);
@@ -287,8 +288,8 @@ void release_task(struct task_struct *p)
 	}
 
 	write_unlock_irq(&tasklist_lock);
+	/* @thread_pid can't go away until free_pids() below */
 	proc_flush_pid(thread_pid);
-	put_pid(thread_pid);
 	add_device_randomness(&p->se.sum_exec_runtime,
 			      sizeof(p->se.sum_exec_runtime));
 	free_pids(post.pids);
-- 
2.47.2


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