From efb29fbfa50c490dac64a9418ebe553be82df781 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 29 Nov 2016 18:51:03 +0100 Subject: [PATCH] kthread: Don't use to_live_kthread() in kthread_stop() kthread_stop() had to use to_live_kthread() simply because it was not possible to access kthread->exited after the exiting task clears task_struct->vfork_done. Now that to_kthread() is always valid, wake_up_process() + wait_for_completion() can be done ununconditionally. It's not an issue anymore if the task has already issued complete_vfork_done() or died. The exiting task can get the spurious wakeup after mm_release() but this is possible without this change too and is fine; do_task_dead() ensures that this can't make any harm. As a further enhancement this could be converted to task_work_add() later, so ->vfork_done can be avoided completely. Signed-off-by: Oleg Nesterov Acked-by: Peter Zijlstra (Intel) Reviewed-by: Thomas Gleixner Cc: Chunming Zhou Cc: Roman Pen Cc: Petr Mladek Cc: Andy Lutomirski Cc: Tejun Heo Cc: Andy Lutomirski Cc: Alex Deucher Cc: Andrew Morton Link: http://lkml.kernel.org/r/20161129175103.GA5336@redhat.com Signed-off-by: Thomas Gleixner --- kernel/kthread.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 7891a940007d..4dcbc8b5d6b6 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -532,13 +532,11 @@ int kthread_stop(struct task_struct *k) trace_sched_kthread_stop(k); get_task_struct(k); - kthread = to_live_kthread(k); - if (kthread) { - set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); - __kthread_unpark(k, kthread); - wake_up_process(k); - wait_for_completion(&kthread->exited); - } + kthread = to_kthread(k); + set_bit(KTHREAD_SHOULD_STOP, &kthread->flags); + __kthread_unpark(k, kthread); + wake_up_process(k); + wait_for_completion(&kthread->exited); ret = k->exit_code; put_task_struct(k); -- 2.20.1