Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753984AbaJBNw6 (ORCPT ); Thu, 2 Oct 2014 09:52:58 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:45509 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753746AbaJBNwy (ORCPT ); Thu, 2 Oct 2014 09:52:54 -0400 Date: Thu, 2 Oct 2014 15:52:50 +0200 From: Peter Zijlstra To: Peter Hurley Cc: Fengguang Wu , Jet Chen , Su Tao , Yuanhan Liu , LKP , linux-kernel@vger.kernel.org, Marcel Holtmann , oleg@redhat.com Subject: Re: [rfcomm_run] WARNING: CPU: 1 PID: 79 at kernel/sched/core.c:7156 __might_sleep() Message-ID: <20141002135250.GB10583@worktop.programming.kicks-ass.net> References: <20140930080228.GD9561@wfg-t540p.sh.intel.com> <20141002110927.GE2849@worktop.programming.kicks-ass.net> <20141002123150.GC6324@worktop.programming.kicks-ass.net> <20141002124247.GD6324@worktop.programming.kicks-ass.net> <542D57D0.4030904@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <542D57D0.4030904@hurleysoftware.com> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 02, 2014 at 09:49:04AM -0400, Peter Hurley wrote: > On 10/02/2014 08:42 AM, Peter Zijlstra wrote: > > On Thu, Oct 02, 2014 at 02:31:50PM +0200, Peter Zijlstra wrote: > >> @@ -2086,24 +2086,22 @@ static void rfcomm_kill_listener(void) > >> > >> static int rfcomm_run(void *unused) > >> { > >> + DEFINE_WAIT_FUNC(wait, woken_wake_function); > >> BT_DBG(""); > >> > >> set_user_nice(current, -10); > >> > >> rfcomm_add_listener(BDADDR_ANY); > >> > >> - while (1) { > >> - set_current_state(TASK_INTERRUPTIBLE); > >> - > >> - if (kthread_should_stop()) > >> - break; > >> + add_wait_queue(&rfcomm_wq, &wait); > >> + while (!kthread_should_stop()) { > >> > >> /* Process stuff */ > >> rfcomm_process_sessions(); > >> > >> - schedule(); > >> + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); > >> } > >> - __set_current_state(TASK_RUNNING); > >> + remove_wait_queue(&rfcomm_wq, &wait); > >> > >> rfcomm_kill_listener(); > >> > > > > Hmm, I think there's a problem there. If someone were to do > > kthread_stop() before wait_woken() we'd not actually stop, because > > wait_woken() doesn't test KTHREAD_SHOULD_STOP before calling schedule(). > > Do you mean this situation? > > CPU 0 | CPU 1 > | > rfcomm_run() | kthread_stop() > ... | > if (!test_bit(KTHREAD_SHOULD_STOP)) | > | set_bit(KTHREAD_SHOULD_STOP) > | wake_up_process() > wait_woken() | wait_for_completion() > set_current_state(INTERRUPTIBLE) | > if (!WQ_FLAG_WOKEN) | > schedule_timeout() | > | > > Now both tasks are sleeping forever. Yep. > If yes, then wakeups from signals don't work either, right? Its a kthread, there should not be any signals. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/