Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755832AbcCEL6x (ORCPT ); Sat, 5 Mar 2016 06:58:53 -0500 Received: from mail-wm0-f67.google.com ([74.125.82.67]:32897 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753628AbcCEL6s (ORCPT ); Sat, 5 Mar 2016 06:58:48 -0500 Date: Sat, 5 Mar 2016 12:58:42 +0100 From: Ingo Molnar To: "Rafael J. Wysocki" Cc: Steve Muckle , "Rafael J. Wysocki" , Linux PM list , Juri Lelli , ACPI Devel Maling List , Linux Kernel Mailing List , Peter Zijlstra , Srinivas Pandruvada , Viresh Kumar , Vincent Guittot , Michael Turquette , Thomas Gleixner , Peter Zijlstra Subject: Re: [PATCH v2 6/10] cpufreq: Support for fast frequency switching Message-ID: <20160305115842.GB11846@gmail.com> References: <2495375.dFbdlAZmA6@vostro.rjw.lan> <2409306.qzzMXcm4dm@vostro.rjw.lan> <15684081.T4iOMUSHCY@vostro.rjw.lan> <56DA09B1.4010005@linaro.org> <56DA20C0.1070803@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 906 Lines: 22 * Rafael J. Wysocki wrote: > > Honestly I wonder if it's better to just try the "no notifiers with fast > > drivers" approach to start. The notifiers could always be added if platform > > owners complain that they absolutely require them. > > Well, I'm not sure what happens if we start to fail notifier registrations. It > may not be a well tested error code path. :-) Yeah, so as a general principle 'struct notifier_block' as a really bad interface with poor and fragile semantics, and we are trying to get rid of them everywhere from core kernel code. For example Thomas Gleixner et al is working on eliminating them from the CPU hotplug code - which will get rid of most remaining notifier uses from the scheduler as well. So please add explicit cpufreq driver callback functions instead, which can be filled in by a platform if needed. No notifiers! Thanks, Ingo