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@redhat.com>
Link: https://lore.kernel.org/20250411121857.GA10550@redhat.com
Reviewed-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index abcd93ce4e18c20d4feac29208dea12742fd571c..c33ecde016deebcaae82da201873dd169f11b3b6 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -258,7 +258,8 @@ repeat:
        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 @@ repeat:
        }
 
        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);