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=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 BCDA5C433E0 for ; Wed, 20 May 2020 19:49:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5053207E8 for ; Wed, 20 May 2020 19:49:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727869AbgETTts (ORCPT ); Wed, 20 May 2020 15:49:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726754AbgETTtp (ORCPT ); Wed, 20 May 2020 15:49:45 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B7BBEC061A0E for ; Wed, 20 May 2020 12:49:45 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jbUiM-0001bM-SA; Wed, 20 May 2020 21:49:19 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 5355A100C99; Wed, 20 May 2020 21:49:18 +0200 (CEST) From: Thomas Gleixner To: paulmck@kernel.org, Andy Lutomirski Cc: LKML , X86 ML , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon , Tom Lendacky , Wei Liu , Michael Kelley , Jason Chen CJ , Zhao Yakui , "Peter Zijlstra \(Intel\)" Subject: Re: [patch V6 12/37] x86/entry: Provide idtentry_entry/exit_cond_rcu() In-Reply-To: <20200520180546.GQ2869@paulmck-ThinkPad-P72> References: <20200515235125.628629605@linutronix.de> <87ftbv7nsd.fsf@nanos.tec.linutronix.de> <87a7237k3x.fsf@nanos.tec.linutronix.de> <874ksb7hbg.fsf@nanos.tec.linutronix.de> <20200520022353.GN2869@paulmck-ThinkPad-P72> <20200520180546.GQ2869@paulmck-ThinkPad-P72> Date: Wed, 20 May 2020 21:49:18 +0200 Message-ID: <87o8qiv135.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Paul E. McKenney" writes: > On Wed, May 20, 2020 at 09:51:17AM -0700, Andy Lutomirski wrote: >> Paul, the major change here is that if an IRQ hits normal kernel code >> (i.e. code where RCU is watching and we're not in an EQS), the IRQ >> won't call rcu_irq_enter() and rcu_irq_exit(). Instead it will call >> rcu_tickle() on entry and nothing on exit. Does that cover all the >> bases? > > From an RCU viewpoint, yes, give or take my concerns about someone > putting rcu_tickle() on entry and rcu_irq_exit() on exit. Perhaps > I can bring some lockdep trickery to bear. An surplus rcu_irq_exit() should already trigger alarms today. > But I must defer to Thomas and Peter on the non-RCU/non-NO_HZ_FULL > portions of this. I don't see a problem. Let me write that into actual testable patch form. Thanks, tglx