From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH] PM: Acquire device locks on suspend Date: Wed, 9 Jan 2008 23:14:48 +0100 Message-ID: <200801092314.49286.rjw@sisk.pl> References: Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:48948 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754053AbYAIWMX (ORCPT ); Wed, 9 Jan 2008 17:12:23 -0500 In-Reply-To: Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Alan Stern Cc: Johannes Berg , Greg KH , Andrew Morton , Len Brown , Ingo Molnar , ACPI Devel Maling List , LKML , pm list On Wednesday, 9 of January 2008, Alan Stern wrote: > On Tue, 8 Jan 2008, Rafael J. Wysocki wrote: > > > Appended is what I managed to put together today. > > > > It probably still has some problems, but I'm not seeing them right now (too > > tired). At least, it doesn't break my system. ;-) > > > > Please review. > > Okay, this seems to be better. I like the way the complicated tests > are all localized in power/main.c. > > In dpm_resume() you shouldn't need to use dpm_list_mtx at all, because > the list_move_tail() comes before the resume_device(). It's the same > as in dpm_power_up(). Still, device_pm_schedule_removal() can (in theory) be called concurrently with dpm_resume() by another thread and this might corrupt the list without the locking. > The same is true for dpm_suspend(). Once all the device have been > locked, there shouldn't be any other tasks accessing the dpm lists. > Hence there should be no need to protect the list. Except for against theoretical races with device_pm_schedule_removal(). > Which reminds me, the kerneldoc for device_pm_schedule_removal() is > inaccurate. The routine always just moves the device to dpm_destroy > list for later processing. Correct. > Also, the kerneldoc for destroy_suspended_device() should contain an > extra paragraph warning that the routine should never be called except > within the scope of a system sleep transition. In practice this means > it has to be directly or indirectly invoked by a suspend or resume > method. Or by a CPU hotplug notifier (that will be the majority of cases, IMO). > It looks good. Thanks for the review. I'll fix the comments and repost the patch from scratch for merging in a separate thread. Greetings, Rafael