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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 3F3B2C433E0 for ; Fri, 12 Jun 2020 19:28:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C363207ED for ; Fri, 12 Jun 2020 19:28:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=amacapital-net.20150623.gappssmtp.com header.i=@amacapital-net.20150623.gappssmtp.com header.b="dhZFlHSQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726352AbgFLT2P (ORCPT ); Fri, 12 Jun 2020 15:28:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45562 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726302AbgFLT2P (ORCPT ); Fri, 12 Jun 2020 15:28:15 -0400 Received: from mail-pf1-x443.google.com (mail-pf1-x443.google.com [IPv6:2607:f8b0:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 44A71C08C5C1 for ; Fri, 12 Jun 2020 12:28:15 -0700 (PDT) Received: by mail-pf1-x443.google.com with SMTP id 64so4757560pfv.11 for ; Fri, 12 Jun 2020 12:28:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amacapital-net.20150623.gappssmtp.com; s=20150623; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=zsiP9iQ9KiOQJSx2zUcdJopzapXweO50L90z0lhR9+4=; b=dhZFlHSQ5y0Nn3ryJaMzoMy/15vrArjg+ifwa8iPrLFnoe6amNlNNkx0GYNBa7V9s3 OozZSabvHjLObtWmECjBNPoYoWpJDxJGzGxEY6D7X7r3q/7lG2TfNtKNECLpfGdiXp1V uS/ePjwyWiSp85V11V+giaEBc9EGiakNP6H4UFDRcjGQmTwBcMeVWX+nMy+BG4rwKTKS SUxlFDLybdbVA+exakNdfYA/pGBccnCyPWy/57Dm1hmORJP2dpUXLzvFhC3YCt1vO4ov B2kmt8hA4z6pDfkkm5EHeFVxSRwK1yusgnqhO+43SWNnXCwsMpU2+I0nS3KUQXA1qwaw CBaA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=zsiP9iQ9KiOQJSx2zUcdJopzapXweO50L90z0lhR9+4=; b=T7xz0ZHAZ+pVnJIo926Lvf9P4P/qK1xdhd+OI3LKz5/7btBFZxtpDHQ8TgDtEhw25a +tzAkvfp8vnaKvu06T1flZuQqhCTPGU0NDelicMx9X9k5ECh+2eA5x77/hwDwW6w/Fef pQH+l9psMt1fRKhnQ08usXRMUuIHq4w4FPa4Mvb6c2crtg/o/BCfuLixejX/QS8CArPZ 4p1rr80JAX5xaRHoWOVE+QMjCNzT7T8C3QPAB2HTazFJ0qRCeJNos7MViyBCugvxA79u ED7WGtPxDaVzqIwdr9NArgDRetViX4eC1SEU8HfqauN7wiz4qwHxu7IRVNtu3UIPJywB xfOA== X-Gm-Message-State: AOAM532xTMJnEMkECREzRYk7levlInsCXtESk/OfxoQU5Bem0NDp009u pj25bOVLV6HXUCaitlzPyu2odQ== X-Google-Smtp-Source: ABdhPJwgHA7//MRGcr/0D8HMMU76zBNsnkEyPAH29sduBCZe1RFg0IURCKWcY6EMZvsXlnYGKiX4iw== X-Received: by 2002:a65:6496:: with SMTP id e22mr12507501pgv.63.1591990093576; Fri, 12 Jun 2020 12:28:13 -0700 (PDT) Received: from ?IPv6:2601:646:c200:1ef2:c0da:d349:5a19:d9c1? ([2601:646:c200:1ef2:c0da:d349:5a19:d9c1]) by smtp.gmail.com with ESMTPSA id 12sm7322426pfb.3.2020.06.12.12.28.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Jun 2020 12:28:12 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [PATCH x86/entry: Force rcu_irq_enter() when in idle task Date: Fri, 12 Jun 2020 12:28:11 -0700 Message-Id: References: <87r1ukxf1b.fsf@nanos.tec.linutronix.de> Cc: paulmck@kernel.org, LKML , rcu@vger.kernel.org, Andrew Lutomirski , X86 ML , Frederic Weisbecker , Steven Rostedt , Joel Fernandes , Mathieu Desnoyers , Will Deacon , Peter Zijlstra In-Reply-To: <87r1ukxf1b.fsf@nanos.tec.linutronix.de> To: Thomas Gleixner X-Mailer: iPhone Mail (17F80) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Jun 12, 2020, at 12:25 PM, Thomas Gleixner wrote: >=20 > =EF=BB=BF"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. >>=20 >> I should add that -your- patch from yesterday did -not- cause this >> problem, in case that is of interest. >=20 > So I still can add it back and amend the changelog and comment: >=20 > 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. >=20 >=20 Can you easily get a call trace for a case where the system is fully booted,= is_idle_task returns false, and rcu_is_watching() also returns false?=