From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S946310AbcJaUIK (ORCPT ); Mon, 31 Oct 2016 16:08:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51592 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S946271AbcJaUH6 (ORCPT ); Mon, 31 Oct 2016 16:07:58 -0400 Date: Mon, 31 Oct 2016 21:07:54 +0100 From: Oleg Nesterov To: Thomas Gleixner Cc: Andy Lutomirski , Roman Pen , Andy Lutomirski , Peter Zijlstra , Ingo Molnar , Tejun Heo , "linux-kernel@vger.kernel.org" , Chunming Zhou , Alex Deucher Subject: [PATCH 1/2] kthread: don't use to_live_kthread() in kthread_stop() Message-ID: <20161031200754.GB19430@redhat.com> References: <20161025110508.9052-1-roman.penyaev@profitbricks.com> <20161025140333.GB4326@redhat.com> <20161025154301.GA12015@redhat.com> <20161026141359.GA6893@redhat.com> <20161026155155.GA28832@redhat.com> <20161028161106.GA8933@redhat.com> <20161031200729.GA19430@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161031200729.GA19430@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 31 Oct 2016 20:07:58 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kthread_stop() had to use to_live_kthread() simply because it was not possible to access kthread->exited after the exiting kthread clears task_struct->vfork_done. Now that to_kthread() is always valid we can do wake_up_process() + wait_for_completion() unconditionally, we don't care if it has already passed complete_vfork_done() or even dead. The exiting kthread can get the spurious wakeup after mm_release() but this is possible without this change too and this is fine, do_task_dead() ensures that this can't make any harm. Note: we can even change this function to use task_work_add() and avoid ->vfork_done altogether, probably we will do this later. Signed-off-by: Oleg Nesterov --- kernel/kthread.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 7891a94..4dcbc8b 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); -- 2.5.0