Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753926Ab3GTMfW (ORCPT ); Sat, 20 Jul 2013 08:35:22 -0400 Received: from mail-ie0-f180.google.com ([209.85.223.180]:62509 "EHLO mail-ie0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753090Ab3GTMfT (ORCPT ); Sat, 20 Jul 2013 08:35:19 -0400 MIME-Version: 1.0 In-Reply-To: References: <1623844.aKWlCHQqy1@vostro.rjw.lan> From: Kay Sievers Date: Sat, 20 Jul 2013 14:34:58 +0200 Message-ID: Subject: Re: udev: New default rule for autoloading kernel modules matching CPU modalias To: "Rafael J. Wysocki" Cc: LKML , Greg Kroah-Hartman , Tim Chen , ACPI Devel Maling List , "H. Peter Anvin" , systemd-devel@lists.freedesktop.org Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2720 Lines: 57 On Sat, Jul 20, 2013 at 1:47 PM, Kay Sievers wrote: > On Sat, Jul 20, 2013 at 12:56 PM, Rafael J. Wysocki wrote: > >> After a recent change present in 3.11-rc1 there is a driver, called processor, >> that can be bound to the CPU devices whose sysfs directories are located under >> /sys/devices/system/cpu/. A side effect of this is that, after the driver has >> been bound to those devices, the kernel adds DRIVER=processor to ENV for CPU >> uevents and they don't match the default rule for autoloading modules matching >> MODALIAS: >> >> DRIVER!="?*", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}" >> >> any more. However, there are some modules whose module aliases match specific >> CPU features through the modalias string and those modules should be loaded >> automatically if a compatible CPU is present. Yet, with the processor driver >> bound to the CPU devices the above rule is not sufficient for that, so we need >> a new default udev rule allowing those modules to be autoloaded even if the >> CPU devices have drivers. >> >> On my test systems I added the following rule for that: >> >> ACTION="add", SUBSYSTEM=="cpu", ENV{MODALIAS}=="?*", IMPORT{builtin}="kmod load $env{MODALIAS}" >> >> in a separate file, but I'm not a udev expert, so I guess it may be done in a >> better way. >> >> Can you please consider adding such a rule to the default set of udev rules? > > The DRIVER!="?*" is an optimization which made a huge difference at > the time we called out to /sbin/modprobe from udev rules and all the > devices which already had a driver would not cause needless execution > of the rather expensive modprobe binary. > > This obviously can't do the right thing for the completely generic, > not bound to a driver-state, CPU modaliases when they have a driver > now. :) > > These days we load the entire kmod modalias database into the udev > process, and lookup what we need to load and load the module from > within the udev worker process. It could be, that the optimization is > not measurable on today's systems, if that's the case I'll remove it, > which would be the simplest and most future proof option. Otherwise > I'll add the CPU specific rule. > > I'll find that out and let you know. I cannot see any measurable difference here that justifies that optimization, so I removed it: http://cgit.freedesktop.org/systemd/systemd/commit/?id=bf7f800f2b3e93ccd1229d4717166f3a4d3af72f Thanks, Kay -- 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/