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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D11E8C4363A for ; Tue, 20 Oct 2020 20:07:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D8AC2225D for ; Tue, 20 Oct 2020 20:07:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2409359AbgJTUHh (ORCPT ); Tue, 20 Oct 2020 16:07:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:53626 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2409326AbgJTUHh (ORCPT ); Tue, 20 Oct 2020 16:07:37 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 241A82225F; Tue, 20 Oct 2020 20:07:35 +0000 (UTC) Date: Tue, 20 Oct 2020 16:07:32 -0400 From: Steven Rostedt To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira Subject: Re: sched: Reenable interrupts in do sched_yield() Message-ID: <20201020160732.5f8fc24e@oasis.local.home> In-Reply-To: <87o8kw93n4.fsf@nanos.tec.linutronix.de> References: <87r1pt7y5c.fsf@nanos.tec.linutronix.de> <20201020113830.378b4a4c@gandalf.local.home> <87o8kw93n4.fsf@nanos.tec.linutronix.de> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 20 Oct 2020 20:02:55 +0200 Thomas Gleixner wrote: > On Tue, Oct 20 2020 at 11:38, Steven Rostedt wrote: > > On Tue, 20 Oct 2020 16:46:55 +0200 > > Thomas Gleixner wrote: > > > >> - /* > >> - * Since we are going to call schedule() anyway, there's > >> - * no need to preempt or enable interrupts: > > > > I think the above comment still makes sense, just needs to be tweeked: > > > > /* > > * Since we are going to call schedule() anyway, there's > > * no need to allow preemption after releasing the rq lock. > >> - */ > > > > Especially, since we are now enabling interrupts, which is likely to > > trigger a preemption. > > sched_preempt_enable_no_resched() still enables preemption. It just > avoids the check. And it still allows preemption when an interrupt > triggering preemption happens between sched_preempt_enable_no_resched() > and __schedule() disabling preemption/interrupts. > > So no, your new variant is just differently bogus and misleading. What I wrote wasn't exactly what I meant. What I meant to have: /* * Since we are going to call schedule() anyways, there's * no need to do the preemption check when the rq_lock is released. */ That is, to document why we have the preempt_disable() before the unlock: preempt_disable(); rq_unlock_irq(rq, &rf); sched_preempt_enable_no_resched(); -- Steve