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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 7AE8FC433E0 for ; Fri, 12 Jun 2020 21:56:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 572DF2078E for ; Fri, 12 Jun 2020 21:56:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591999015; bh=mWMXi6xqoC2+eKZfze2WcCelGr8w6FXyOKbi5oEX2as=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=KhRJmvH2NTLJiYH7YfJIgMt8XaP0TvqG7GSqLbYFVDhES2ckAu8DQBdoe+MeVMmZw gVgZdNsYiKRTItfl0r4uFC1zcl6kY4ME7q6IrvGWP8IPR00wHgfjSmdt+jVcQOJOaH NVGPB4iJtIidZhq8zzwpW7btmpvjzsR0d2fbo94c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726358AbgFLV4w (ORCPT ); Fri, 12 Jun 2020 17:56:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:45036 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726304AbgFLV4v (ORCPT ); Fri, 12 Jun 2020 17:56:51 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (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 82F20206DC; Fri, 12 Jun 2020 21:56:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591999010; bh=mWMXi6xqoC2+eKZfze2WcCelGr8w6FXyOKbi5oEX2as=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=A89F5YbzfyufclIGNaDWvLyh8iSo6b5hovTNFiZUqBJpsGz3YmoS7w6xOfYusMRS/ SRYicMV62L9j+NhNJHd/4uia8P7y/oDvJTsnjuM7mRWDZtZrkEEFEhy08Hd2MjlUs1 oSjTSce0+m45Dr/RGoffJyPyMnk2El/1r7ySNGzM= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 69EBD3522658; Fri, 12 Jun 2020 14:56:50 -0700 (PDT) Date: Fri, 12 Jun 2020 14:56:50 -0700 From: "Paul E. McKenney" To: Thomas Gleixner Cc: LKML , rcu@vger.kernel.org, Andrew Lutomirski , X86 ML , Frederic Weisbecker , Steven Rostedt , Joel Fernandes , Mathieu Desnoyers , Will Deacon , Peter Zijlstra Subject: Re: [PATCH x86/entry: Force rcu_irq_enter() when in idle task Message-ID: <20200612215650.GN4455@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <87r1ukxf1b.fsf@nanos.tec.linutronix.de> <87k10ccc2n.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87k10ccc2n.fsf@nanos.tec.linutronix.de> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 12, 2020 at 09:34:56PM +0200, Thomas Gleixner wrote: > Thomas Gleixner writes: > > > "Paul E. McKenney" writes: > >> On Fri, Jun 12, 2020 at 10:49:53AM -0700, Paul E. McKenney wrote: > >>> I will therefore address this issue in a follow-on patch. > >> > >> I should add that -your- patch from yesterday did -not- cause this > >> problem, in case that is of interest. > > > > So I still can add it back and amend the changelog and comment: > > > > Change the condition from !rcu_is_watching() to is_idle_task(current) || > > rcu_is_watching() which enforces that interrupts in the idle task > > unconditionally invoke rcu_irq_enter() independent of the RCU state. For > > most scenarios is_idle_task() would be sufficient but Task RCU needs it > > according to Paul. > > After talking to Paul some more we came to the conclusion that the > failure scenario of task rcu is not completely clear and the trigger > scenario is obscure enough. This needs more investigation and the > important part which we were chasing is fixed and agreed on. So I go > with the simple version now and Paul will follow up once it can be > properly explained. So the whole TASKS03 failure issue turned out to be me applying the wrong patches onto the wrong commits. Retesting with -tip x86/entry passes TASKS03, as in more than 100 instances of it. I am rerunning the whole stack, but I don't see the need to wait for that. (I will be running increasingly long tests over Friday night, Pacific Time.) Thanx, Paul