Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755035Ab0K3W2V (ORCPT ); Tue, 30 Nov 2010 17:28:21 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:43108 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754822Ab0K3W2S (ORCPT ); Tue, 30 Nov 2010 17:28:18 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [PATCH] PM: Prevent dpm_prepare() from returning errors unnecessarily Date: Tue, 30 Nov 2010 23:27:24 +0100 User-Agent: KMail/1.13.5 (Linux/2.6.37-rc4+; KDE/4.4.4; x86_64; ; ) Cc: "Linux-pm mailing list" , LKML , Ming Lei References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201011302327.24222.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2080 Lines: 52 On Tuesday, November 30, 2010, Alan Stern wrote: > On Mon, 29 Nov 2010, Rafael J. Wysocki wrote: > > > > Oh, I see. This is a tricky issue. Every driver for a device that can > > > have wakeup-enabled children needs to worry about the race between > > > suspending the device and receiving a wakeup request from a child. > > > For example, in drivers/usb/core/hcd-pci.c, the suspend_common() > > > routine goes out of its way to return -EBUSY if device_may_wakeup() is > > > true and the controller's root hub has a pending wakeup request. > > > > > > How should drivers handle this in general? Should we make an effort to > > > convert them to use the wakeup framework so they they can let the PM > > > core take care of these races? > > > > I think so. > > > > We also need to put a pm_check_wakeup_events() check into dpm_suspend() IMO, > > so that we abort the suspending of devices as soon as a wakeup event is > > reported. > > You might as well add that into this patch. I'll do that in a separate patch. > > > Do we have to consider similar races during runtime suspend? > > > > Ideally, yes, but I'm not sure if that's generally possible. IMO, it won't be > > a big deal if a parent device is suspended and immediately resumed occasionally > > due to a pending wakeup signal from one of its children. It may be a problem > > if that happens too often, though. > > Okay. > > > Does it mean you're fine with the patch? > > Provided you repair the error that Lei Ming pointed out. That's the > problem with functions that return Boolean values -- you have to name > them very carefully. Ideally the name should be a predicate or a > question. I already have fixed it. The name is unfortunate indeed, perhaps it's better to call that function pm_new_wakeup_events() or something like this. Thanks, Rafael -- 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/