From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C27EBCE79A9 for ; Tue, 19 Sep 2023 16:42:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231736AbjISQmN (ORCPT ); Tue, 19 Sep 2023 12:42:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230137AbjISQmJ (ORCPT ); Tue, 19 Sep 2023 12:42:09 -0400 Received: from www.kot-begemot.co.uk (ns1.kot-begemot.co.uk [217.160.28.25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 92CEAD6; Tue, 19 Sep 2023 09:42:02 -0700 (PDT) Received: from [192.168.17.6] (helo=jain.kot-begemot.co.uk) by www.kot-begemot.co.uk with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1qidmu-002SbU-Ay; Tue, 19 Sep 2023 16:41:24 +0000 Received: from jain.kot-begemot.co.uk ([192.168.3.3]) by jain.kot-begemot.co.uk with esmtp (Exim 4.94.2) (envelope-from ) id 1qidmr-00FzAL-KO; Tue, 19 Sep 2023 17:41:23 +0100 Message-ID: Date: Tue, 19 Sep 2023 17:41:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: Arches that don't support PREEMPT Content-Language: en-US To: Richard Weinberger Cc: tglx , Peter Zijlstra , John Paul Adrian Glaubitz , Matthew Wilcox , torvalds , Ankur Arora , linux-kernel , linux-mm , x86 , Andrew Morton , Andy Lutomirski , bp , dave hansen , hpa , mingo , juri lelli , vincent guittot , mgorman@suse.de, Steven Rostedt , jon grimm , bharata@amd.com, raghavendra kt , boris ostrovsky , konrad wilk , jgross , andrew cooper3 , Geert Uytterhoeven , linux-m68k , Johannes Berg , linux-um , Brian Cain , linux-hexagon@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , linux-alpha References: <87zg1u1h5t.fsf@oracle.com> <87led2wdj0.ffs@tglx> <0e69f7df80dc5878071deb0d80938138d19de1d1.camel@physik.fu-berlin.de> <20230919134218.GA39281@noisy.programming.kicks-ass.net> <87y1h2ur98.ffs@tglx> <9a5c0856-d542-9912-7494-53d7fe4538a3@cambridgegreys.com> <551475267.58816.1695140566849.JavaMail.zimbra@nod.at> From: Anton Ivanov In-Reply-To: <551475267.58816.1695140566849.JavaMail.zimbra@nod.at> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Clacks-Overhead: GNU Terry Pratchett Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/09/2023 17:22, Richard Weinberger wrote: > ----- Ursprüngliche Mail ----- >> Von: "anton ivanov" >> It's been a while. I remember that I dropped it at the time, but do not remember >> the full details. >> >> There was some stuff related to FP state and a few other issues I ran into while >> rewriting the interrupt controller. Some of it may be resolved by now as we are >> using host cpu flags, etc. > > I remember also having a hacky but working version almost 10 years ago. > It was horrible slow because of the extra scheduler rounds. > But yes, if PREEMPT will be a must-have feature we'll have to try again. We will need proper fpu primitives for starters that's for sure. fpu_star/end in UML are presently NOOP. Some of the default spinlocks and other stuff which we pick up from generic may need to change as well. This is off the top of my head and something which we can fix straight away. I will send some patches to the mailing list tomorrow or on Thu. A. > > Thanks, > //richard > > _______________________________________________ > linux-um mailing list > linux-um@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-um -- Anton R. Ivanov Cambridgegreys Limited. Registered in England. Company Number 10273661 https://www.cambridgegreys.com/