From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754303Ab2KZTIW (ORCPT ); Mon, 26 Nov 2012 14:08:22 -0500 Received: from mail.kernel.org ([198.145.19.201]:57675 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753537Ab2KZTIV (ORCPT ); Mon, 26 Nov 2012 14:08:21 -0500 Date: Mon, 26 Nov 2012 11:08:18 -0800 From: Greg Kroah-Hartman To: Huang Ying Cc: Ben Hutchings , linux-kernel@vger.kernel.org, stable@vger.kernel.org, alan@lxorguk.ukuu.org.uk, Bjorn Helgaas , "Rafael J. Wysocki" , Zhang Yanmin Subject: Re: [ 02/38] PCI/PM: Fix deadlock when unbinding device if parent in D3cold Message-ID: <20121126190818.GA22409@kroah.com> References: <20121122003904.262382971@linuxfoundation.org> <20121122003904.516735571@linuxfoundation.org> <1353638130.4764.4.camel@deadeye.wl.decadent.org.uk> <1353640177.28789.21.camel@yhuang-dev> <20121126185505.GE21012@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20121126185505.GE21012@kroah.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 26, 2012 at 10:55:05AM -0800, Greg Kroah-Hartman wrote: > On Fri, Nov 23, 2012 at 11:09:37AM +0800, Huang Ying wrote: > > On Fri, 2012-11-23 at 02:35 +0000, Ben Hutchings wrote: > > > On Wed, 2012-11-21 at 16:39 -0800, Greg Kroah-Hartman wrote: > > > > 3.0-stable review patch. If anyone has any objections, please let me know. > > > > > > > > ------------------ > > > > > > > > From: Huang Ying > > > > > > > > commit 90b5c1d7c45eeb622302680ff96ed30c1a2b6f0e upstream. > > > > > > > > If a PCI device and its parents are put into D3cold, unbinding the > > > > device will trigger deadlock as follow: > > > > > > > > - driver_unbind > > > > - device_release_driver > > > > - device_lock(dev) <--- previous lock here > > > > - __device_release_driver > > > > - pm_runtime_get_sync > > > > ... > > > > - rpm_resume(dev) > > > > - rpm_resume(dev->parent) > > > > ... > > > > - pci_pm_runtime_resume > > > > ... > > > > - pci_set_power_state > > > > - __pci_start_power_transition > > > > - pci_wakeup_bus(dev->parent->subordinate) > > > > - pci_walk_bus > > > > - device_lock(dev) <--- deadlock here > > > > > > > > > > > > If we do not do device_lock in pci_walk_bus, we can avoid deadlock. > > > > Device_lock in pci_walk_bus is introduced in commit: > > > > d71374dafbba7ec3f67371d3b7e9f6310a588808, corresponding email thread > > > > is: https://lkml.org/lkml/2006/5/26/38. The patch author Zhang Yanmin > > > > said device_lock is added to pci_walk_bus because: > > > > > > > > Some error handling functions call pci_walk_bus. For example, PCIe > > > > aer. Here we lock the device, so the driver wouldn't detach from the > > > > device, as the cb might call driver's callback function. > > > > > > > > So I fixed the deadlock as follows: > > > > > > > > - remove device_lock from pci_walk_bus > > > > - add device_lock into callback if callback will call driver's callback > > > > > > > > I checked pci_walk_bus users one by one, and found only PCIe aer needs > > > > device lock. > > > [...] > > > > > > What about eeh_report_error() in > > > arch/powerpc/platforms/pseries/eeh_driver.c? > > > > En... Because pci_walk_bus() invocation is removed in 3.7, so this > > patch is only valid for 3.7. We need another version for 3.6. > > > > > Also, is the deadlock even possible before this change in Linux 3.6? > > > > > > commit 448bd857d48e69b33ef323739dc6d8ca20d4cda7 > > > Author: Huang Ying > > > Date: Sat Jun 23 10:23:51 2012 +0800 > > > > > > PCI/PM: add PCIe runtime D3cold support > > > > Before this, there will be no deadlock. So we do not need fixes before > > Linux 3.6. > > So the first patch mentioned here should not be included in the 3.0 and > 3.4 stable kernel releases? Ok, I've dropped the patch from 3.0 and 3.4-stable trees now. For 3.6, what should I do? thanks, greg k-h