Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757524AbXE1LQP (ORCPT ); Mon, 28 May 2007 07:16:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750729AbXE1LQB (ORCPT ); Mon, 28 May 2007 07:16:01 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:36168 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750724AbXE1LQA (ORCPT ); Mon, 28 May 2007 07:16:00 -0400 Date: Mon, 28 May 2007 13:15:54 +0200 From: Pavel Machek To: "Rafael J. Wysocki" Cc: Kay Sievers , Matthew Garrett , pm list , LKML , Nigel Cunningham , Alan Stern , Oliver Neukum Subject: Re: [RFC][PATCH -mm 3/3] PM: Disable _request_firmware before hibernation/suspend Message-ID: <20070528111554.GF18807@elf.ucw.cz> References: <200705272229.21263.rjw@sisk.pl> <20070527220412.GC22687@srcf.ucam.org> <1180304166.3131.66.camel@lov.localdomain> <200705280943.54312.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200705280943.54312.rjw@sisk.pl> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1989 Lines: 44 Hi! > > > > What exactly is the problem we see here? The timeout of the firmware loader? > > > > What goes wrong with frozen userspace, usually there is only a netlink > > > > message sent from the kernel, which should be received and handled > > > > just fine when userspace is running again. > > > > > > Driver calls request_firmware in the resume method. The userspace helper > > > can't be run because it's been frozen, so the firmware never gets loaded > > > and the call times out. The driver then fails to resume. While all this > > > is happening, the rest of the kernel is blocking on that resume method. > > > The firmware can be loaded once userspace has been started again, but by > > > that time the driver has given up. > > > > Seems, that's just the broken synchronous firmware loading interface > > with the useless timeout handling. The nowait version of the same loader > > doesn't time out, and should not have that problem. The sync version > > should be removed from the kernel, it just causes all sorts of problems > > since it exists. > > > > Userspace should handle the async request just fine when it comes back > > running, regardless of the time it was submitted. > > Okay, so the solution is to convert the drivers to use > request_firmware_nowait() instead of request_firmware() in their .resume() > routines. You'll just get deadlock at different level (and more rare). Imagine disk with its firmware on NFS and NFS with its firmware on disk. (Or maybe firmware loader doing find /, including both disk and NFS). Just don't call request_firmware_* from .resume(). -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/