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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 890CEC2D0A3 for ; Mon, 16 Nov 2020 20:00:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2246D20A8B for ; Mon, 16 Nov 2020 20:00:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="xvJayIxU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730979AbgKPUAG (ORCPT ); Mon, 16 Nov 2020 15:00:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:47620 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727393AbgKPUAF (ORCPT ); Mon, 16 Nov 2020 15:00:05 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (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 05513208C7; Mon, 16 Nov 2020 20:00:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605556805; bh=yrjw14o5asHTeWaBifST22KQ0VTjN4jtabHNixcSZg8=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=xvJayIxUQqCdvK00oNaDZUoCwldmZpK9t+nF/q8zXZ/vJoo6GtsSDVb0rKmS0ZKWo 1ppPCmwd6pMm2rCW3fXARbNWyc3N5dDRaspywlG/dMdRXU+fJsPNiSFaIUVb6AFx95 +qRtSTNX8aKdC9mLtG8zJ4kjL6XsB9MVqsWqT+gY= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 96C973522684; Mon, 16 Nov 2020 12:00:04 -0800 (PST) Date: Mon, 16 Nov 2020 12:00:04 -0800 From: "Paul E. McKenney" To: Thomas Gleixner Cc: Peter Zijlstra , eupm90@gmail.com, linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Steven Rostedt Subject: Re: [PATCH] rcu: Allow rcu_irq_enter_check_tick() from NMI Message-ID: <20201116200004.GD1437@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20201113125332.GA2611@hirez.programming.kicks-ass.net> <87ima8luix.fsf@nanos.tec.linutronix.de> <20201114010526.GK3249@paulmck-ThinkPad-P72> <20201116121012.GC3121378@hirez.programming.kicks-ass.net> <87a6vhz034.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87a6vhz034.fsf@nanos.tec.linutronix.de> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 16, 2020 at 06:24:31PM +0100, Thomas Gleixner wrote: > On Mon, Nov 16 2020 at 13:10, Peter Zijlstra wrote: > > > Any which way around; here's a proper patch... > > > > --- > > > > Subject: rcu: Allow rcu_irq_enter_check_tick() from NMI > > From: Peter Zijlstra > > Date: Mon Nov 16 12:54:56 CET 2020 > > > > Eugenio managed to tickle #PF from NMI context which resulted in > > hitting a WARN in RCU through irqentry_enter() -> > > __rcu_irq_enter_check_tick(). > > > > However, this situation is perfectly sane and does not warrant an > > WARN. The #PF will (necessarily) be atomic and not require messing > > with the tick state, so early return is correct. > > > > Fixes: aaf2bc50df1f ("rcu: Abstract out rcu_irq_enter_check_tick() from rcu_nmi_enter()") > > Reported-by: "Eugenio Pérez" > > Signed-off-by: Peter Zijlstra (Intel) > > Reviewed-by: Andy Lutomirski > > Reviewed-by: Paul E. McKenney > > Reviewed-by: Thomas Gleixner Queued, thank you all! Thanx, Paul