Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754348AbaJBNtM (ORCPT ); Thu, 2 Oct 2014 09:49:12 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:47893 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751815AbaJBNtJ (ORCPT ); Thu, 2 Oct 2014 09:49:09 -0400 Message-ID: <542D57D0.4030904@hurleysoftware.com> Date: Thu, 02 Oct 2014 09:49:04 -0400 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.1.2 MIME-Version: 1.0 To: Peter Zijlstra , Fengguang Wu CC: 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() 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> In-Reply-To: <20141002124247.GD6324@worktop.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. If yes, then wakeups from signals don't work either, right? Regards, Peter Hurley -- 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/