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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable 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 C170EC3403D for ; Tue, 18 Feb 2020 14:41:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A3B55208C4 for ; Tue, 18 Feb 2020 14:41:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726962AbgBROl2 (ORCPT ); Tue, 18 Feb 2020 09:41:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:60178 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726116AbgBROl2 (ORCPT ); Tue, 18 Feb 2020 09:41:28 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 9C2F020801; Tue, 18 Feb 2020 14:41:26 +0000 (UTC) Date: Tue, 18 Feb 2020 09:41:24 -0500 From: Steven Rostedt To: "Paul E. McKenney" Cc: Lai Jiangshan , Boqun Feng , linux-kernel@vger.kernel.org, Josh Triplett , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu@vger.kernel.org, Peter Zijlstra , Borislav Petkov , Sebastian Andrzej Siewior Subject: Re: [PATCH V2 2/7] rcu: cleanup rcu_preempt_deferred_qs() Message-ID: <20200218094124.339c0315@gandalf.local.home> In-Reply-To: <20200217232307.GA17570@paulmck-ThinkPad-P72> References: <20191102124559.1135-1-laijs@linux.alibaba.com> <20191102124559.1135-3-laijs@linux.alibaba.com> <20191103020150.GA23770@tardis> <7489f817-adaf-275b-b19d-18ad248b071f@linux.alibaba.com> <20191104145539.GY20975@paulmck-ThinkPad-P72> <20191105071911.GL20975@paulmck-ThinkPad-P72> <20191111143238.GA13306@paulmck-ThinkPad-P72> <20200217232307.GA17570@paulmck-ThinkPad-P72> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 17 Feb 2020 15:23:07 -0800 "Paul E. McKenney" wrote: > > I'm still asking for more comments. > > > > By now, I have received some precious comments, mainly due to my > > stupid naming mistakes and a misleading changelog. I should have How about typos? > > updated all these with a new series patches. But I hope I > > can polish more in the new patchset with more suggestions from > > valuable comments, especially in x86,scheduler,percpu and rcu > > areas. > > > > I'm very obliged to hear anything. > > commit 23a58acde0eea57ac77377e5d50d9562b2dbdfaa > Author: Lai Jiangshan > Date: Sat Feb 15 14:37:26 2020 -0800 > > rcu: Don't set nesting depth negative in rcu_preempt_deferred_qs() > > Now that RCU flavors have been consolidated, an RCU-preempt > rcu_rea_unlock() in an interrupt or softirq handler cannot possibly What's a "rea"? ;-) -- Steve > end the RCU read-side critical section. Consider the old vulnerability > involving rcu_preempt_deferred_qs() being invoked within such a handler > that interrupted an extended RCU read-side critical section, in which > a wakeup might be invoked with a scheduler lock held. Because > rcu_read_unlock_special() no longer does wakeups in such situations, > it is no longer necessary for rcu_preempt_deferred_qs() to set the > nesting level negative. > > This commit therfore removes this recursion-protection code from > rcu_preempt_deferred_qs(). > > Signed-off-by: Lai Jiangshan > Signed-off-by: Paul E. McKenney > >