Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752191AbaJBTOf (ORCPT ); Thu, 2 Oct 2014 15:14:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49078 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751357AbaJBTOe (ORCPT ); Thu, 2 Oct 2014 15:14:34 -0400 Date: Thu, 2 Oct 2014 21:11:14 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: Peter Hurley , Fengguang Wu , Jet Chen , Su Tao , Yuanhan Liu , LKP , linux-kernel@vger.kernel.org, Marcel Holtmann Subject: Re: [rfcomm_run] WARNING: CPU: 1 PID: 79 at kernel/sched/core.c:7156 __might_sleep() Message-ID: <20141002191114.GA30606@redhat.com> 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> <20141002135250.GB10583@worktop.programming.kicks-ass.net> <20141002135805.GF6324@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141002135805.GF6324@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/02, Peter Zijlstra wrote: > > On Thu, Oct 02, 2014 at 03:52:50PM +0200, Peter Zijlstra wrote: > > > If yes, then wakeups from signals don't work either, right? > > > > Its a kthread, there should not be any signals. > > That said, in the tty patch we do appear to have this problem. > > Oleg, do we want something like the below on top to make that work > again? > > --- > --- a/kernel/sched/wait.c > +++ b/kernel/sched/wait.c > @@ -326,8 +326,10 @@ long wait_woken(wait_queue_t *wait, unsi > * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must > * also observe all state before the wakeup. > */ > - if (!(wait->flags & WQ_FLAG_WOKEN)) > - timeout = schedule_timeout(timeout); > + if (!(wait->flags & WQ_FLAG_WOKEN)) { > + if (___wait_is_interruptible(mode) && !signal_pending_state(mode, current)) > + timeout = schedule_timeout(timeout); > + } > __set_current_state(TASK_RUNNING); I am a bit confused... but for what? schedule() won't sleep if signal_pending_state(mode) anyway, so we do not need this correctness-wise. And the caller needs to check signal_pending() anyway. We can probably add if (signal_pending_state(mode, current)) return -EINTR; at the start of wait_woken(), even before set_current_state(mode). Then the caller can check "ret < 0" and avoid signal_pending(). Not sure this makes sense. Oleg. -- 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/