Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757534Ab3EHQPf (ORCPT ); Wed, 8 May 2013 12:15:35 -0400 Received: from cantor2.suse.de ([195.135.220.15]:37845 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757452Ab3EHQPc (ORCPT ); Wed, 8 May 2013 12:15:32 -0400 Date: Wed, 08 May 2013 18:15:33 +0200 Message-ID: From: Takashi Iwai To: Ming Lei Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman Subject: Re: [PATCH 2/3] firmware: Avoid deadlock of usermodehelper lock at shutdown In-Reply-To: References: <1367996197-32748-1-git-send-email-tiwai@suse.de> <1367996197-32748-3-git-send-email-tiwai@suse.de> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.2 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1702 Lines: 48 At Wed, 8 May 2013 23:56:51 +0800, Ming Lei wrote: > > On Wed, May 8, 2013 at 2:56 PM, Takashi Iwai wrote: > > When a system goes to reboot/shutdown, it tries to disable the > > usermode helper via usermodehelper_disable(). This might be blocked > > when a driver tries to load a firmware beforehand and it's stuck by > > some reason. > > IMO, it is better to find why the loading is stuck. Also we already provides > the timeout sysfs file to help to deal with the situation. The loading is done manually in the case of dell_rbu driver, so it may happen at any time that the f/w loading doesn't finish properly. > > In this patch, the firmware class driver registers a reboot notifier > > so that it can abort all pending f/w bufs. Also enable a flag for > > avoiding the call of usermodehelper after the reboot/shutdown starts. > > With this patch, maybe we only hide the real problem. No, you can simulate the hang easily. Try the below (you can run it on every x86 machine; it just loads the data onto the memory.) - modprobe dell_rbu - echo init > /sys/devices/platform/dell_rbu/image_type (... now /sys/class/firmware/dell_rbu/* appear) - echo 1 > /sys/class/firmware/dell_rbu/loading - halt -p Now the machine gets stuck. Yes, the real problem is obvious: you didn't finish the f/w loading in the above, and it will never happen. This doesn't justify that the machine can be stalled at shutdown, though. Takashi -- 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/