Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752577AbaJBMmv (ORCPT ); Thu, 2 Oct 2014 08:42:51 -0400 Received: from casper.infradead.org ([85.118.1.10]:56283 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751331AbaJBMmu (ORCPT ); Thu, 2 Oct 2014 08:42:50 -0400 Date: Thu, 2 Oct 2014 14:42:47 +0200 From: Peter Zijlstra To: Fengguang Wu Cc: Jet Chen , Su Tao , Yuanhan Liu , LKP , linux-kernel@vger.kernel.org, Marcel Holtmann , Peter Hurley , oleg@redhat.com Subject: Re: [rfcomm_run] WARNING: CPU: 1 PID: 79 at kernel/sched/core.c:7156 __might_sleep() Message-ID: <20141002124247.GD6324@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141002123150.GC6324@worktop.programming.kicks-ass.net> 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 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(). We can't unconditionally put a kthread_should_stop() in because to_kthread() would explode on a !kthread. The other obvious solution is adding a second function, something like wait_woken_or_stop(), but that appears somewhat ugly to me. Oleg, do you see another solution? -- 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/