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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 26E0EC432C1 for ; Tue, 24 Sep 2019 16:06:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 082D320673 for ; Tue, 24 Sep 2019 16:06:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2438854AbfIXQF6 (ORCPT ); Tue, 24 Sep 2019 12:05:58 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:34736 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2438777AbfIXQF6 (ORCPT ); Tue, 24 Sep 2019 12:05:58 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1iCnK6-0006K0-L0; Tue, 24 Sep 2019 18:05:54 +0200 Date: Tue, 24 Sep 2019 18:05:54 +0200 From: Sebastian Andrzej Siewior To: Scott Wood Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E . McKenney" , Joel Fernandes , Thomas Gleixner , Steven Rostedt , Peter Zijlstra , Juri Lelli , Clark Williams Subject: Re: [PATCH RT v3 3/5] sched: migrate_dis/enable: Use rt_invol_sleep Message-ID: <20190924160554.5esplbmnzm4q4tew@linutronix.de> References: <20190911165729.11178-1-swood@redhat.com> <20190911165729.11178-4-swood@redhat.com> <20190917075943.qsaakyent4dxjkq4@linutronix.de> <779eddcc937941e65659a11b1867c6623a2c8890.camel@redhat.com> <404575720cf24765e66020f15ce75352f08a0ddb.camel@redhat.com> <20190923175233.yub32stn3xcwkaml@linutronix.de> <20190924112155.rxeyksetgqmer3pg@linutronix.de> <55dc19fcc44b2e658b71f68206306c8310335564.camel@redhat.com> <20190924152514.enzeuoo5a6o3mgqu@linutronix.de> <1a2234884e55e5ee6df5f32f828a99c1b248933f.camel@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1a2234884e55e5ee6df5f32f828a99c1b248933f.camel@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 2019-09-24 10:47:36 [-0500], Scott Wood wrote: > When the stop machine finishes it will do a wake_up_process() via > complete(). Since this does not pass WF_LOCK_SLEEPER, saved_state will be > cleared, and you'll have TASK_RUNNING when you get to other_func() and > schedule(), regardless of whether CPU1 sends wake_up() -- so this change > doesn't actually accomplish anything. True, I completely missed that part. > While as noted in the other thread I don't think these spurious wakeups are > a huge problem, we could avoid them by doing stop_one_cpu_nowait() and then > schedule() without messing with task state. Since we're stopping our own > cpu, it should be guaranteed that the stopper has finished by the time we > exit schedule(). I remember loosing a state can be a problem. Lets say it is not "just" TASK_UNINTERRUPTIBLE -> TASK_RUNNING which sounds harmless but it is __TASK_TRACED and you lose it as part of unlocking siglock. > -Scott Sebastian