Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758144AbYAFNRd (ORCPT ); Sun, 6 Jan 2008 08:17:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754397AbYAFNRY (ORCPT ); Sun, 6 Jan 2008 08:17:24 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:60269 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754275AbYAFNRX (ORCPT ); Sun, 6 Jan 2008 08:17:23 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [PATCH] PM: Acquire device locks on suspend Date: Sun, 6 Jan 2008 14:19:51 +0100 User-Agent: KMail/1.9.6 (enterprise 20070904.708012) Cc: Greg KH , Andrew Morton , Len Brown , Ingo Molnar , ACPI Devel Maling List , LKML , pm list References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200801061419.52277.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2361 Lines: 67 On Sunday, 6 of January 2008, Alan Stern wrote: > On Sat, 5 Jan 2008, Rafael J. Wysocki wrote: > > > On Saturday, 5 of January 2008, Alan Stern wrote: > > > On Sat, 5 Jan 2008, Rafael J. Wysocki wrote: > > > > > Still, even doing that is not enough, since someone can call > > > > destroy_suspended_device() from a .suspend() routine and then the device > > > > will end up on a wrong list just as well. > > > > > > That should never happen. The whole idea of destroy_suspended_device() > > > is that the device couldn't be resumed and in fact should be > > > unregistered because it is no longer working or no longer present. A > > > suspend routine won't detect this sort of thing since it doesn't try to > > > resume the device. > > > > > > But it wouldn't hurt to mention in the kerneldoc that > > > destroy_suspended_device() is meant to be called only during a system > > > resume. > > > > Hmm. Please have a look at the appended patch. > > > > I have removed the warning from device_del() and used list_empty() to detect > > removed devices in the .suspend() routines. Is that viable? > > It's not good. > > The warning in device_del() is vital. It's what will tell people where > the problem is when a deadlock occurs during system resume because some > driver has mistakenly tried to unregister a device at the wrong time. > It would have pointed immediately to the msr driver in the case of the > bug Andrew found, for instance. > > If you can figure out a way to disable the warning in device_del() for > just the one device being unregistered by > device_pm_destroy_suspended(), Something like this, perhaps: @@ -905,6 +915,18 @@ void device_del(struct device * dev) struct device * parent = dev->parent; struct class_interface *class_intf; + if (down_trylock(&dev->sem)) { + if (pm_sleep_lock()) { + dev_warn(dev, "Illegal %s during suspend\n", + __FUNCTION__); + dump_stack(); + } else { + pm_sleep_unlock(); + } + } else { + up(&dev->sem); + } + if (parent) klist_del(&dev->knode_parent); if (MAJOR(dev->devt)) > I suppose that would be okay. 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/