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=-11.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 F0DC1C54E8D for ; Mon, 11 May 2020 21:00:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D529820836 for ; Mon, 11 May 2020 21:00:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732139AbgEKVAP (ORCPT ); Mon, 11 May 2020 17:00:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44090 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1732029AbgEKU74 (ORCPT ); Mon, 11 May 2020 16:59:56 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E589BC061A0C; Mon, 11 May 2020 13:59:55 -0700 (PDT) Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jYFWi-0005w4-EQ; Mon, 11 May 2020 22:59:52 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id EE04A1C0861; Mon, 11 May 2020 22:59:37 +0200 (CEST) Date: Mon, 11 May 2020 20:59:37 -0000 From: "tip-bot2 for Lai Jiangshan" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/rcu] rcu: Don't set nesting depth negative in rcu_preempt_deferred_qs() Cc: Lai Jiangshan , "Paul E. McKenney" , x86 , LKML MIME-Version: 1.0 Message-ID: <158923077786.390.1485983578500795487.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit 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 The following commit has been merged into the core/rcu branch of tip: Commit-ID: 07b4a930fc44a537efecf73c1fd2b4937f64caaa Gitweb: https://git.kernel.org/tip/07b4a930fc44a537efecf73c1fd2b4937f64caaa Author: Lai Jiangshan AuthorDate: Sat, 15 Feb 2020 14:37:26 -08:00 Committer: Paul E. McKenney CommitterDate: Mon, 27 Apr 2020 11:03:50 -07:00 rcu: Don't set nesting depth negative in rcu_preempt_deferred_qs() Now that RCU flavors have been consolidated, an RCU-preempt rcu_read_unlock() in an interrupt or softirq handler cannot possibly 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 therefore removes this recursion-protection code from rcu_preempt_deferred_qs(). [ paulmck: Fix typo in commit log per Steve Rostedt. ] Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_plugin.h | 5 ----- 1 file changed, 5 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ccad776..263c766 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -569,16 +569,11 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) static void rcu_preempt_deferred_qs(struct task_struct *t) { unsigned long flags; - bool couldrecurse = rcu_preempt_depth() >= 0; if (!rcu_preempt_need_deferred_qs(t)) return; - if (couldrecurse) - rcu_preempt_depth_set(rcu_preempt_depth() - RCU_NEST_BIAS); local_irq_save(flags); rcu_preempt_deferred_qs_irqrestore(t, flags); - if (couldrecurse) - rcu_preempt_depth_set(rcu_preempt_depth() + RCU_NEST_BIAS); } /*