From patchwork Tue Apr 14 08:20:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: thermal-bot for Julien Panis X-Patchwork-Id: 227961 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, URIBL_BLOCKED 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 CC0C6C2BA19 for ; Tue, 14 Apr 2020 08:23:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2D1F206E9 for ; Tue, 14 Apr 2020 08:23:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436527AbgDNIVi (ORCPT ); Tue, 14 Apr 2020 04:21:38 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:43009 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2407121AbgDNIUx (ORCPT ); Tue, 14 Apr 2020 04:20:53 -0400 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 1jOGoK-0006GN-5i; Tue, 14 Apr 2020 10:20:48 +0200 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 7E7DB1C0086; Tue, 14 Apr 2020 10:20:47 +0200 (CEST) Date: Tue, 14 Apr 2020 08:20:47 -0000 From: "tip-bot2 for Paul E. McKenney" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/urgent] rcu: Don't acquire lock in NMI handler in rcu_nmi_enter_common() Cc: Thomas Gleixner , "Paul E. McKenney" , "Joel Fernandes (Google)" , , x86 , LKML MIME-Version: 1.0 Message-ID: <158685244710.28353.3404230640093238216.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails 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: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The following commit has been merged into the core/urgent branch of tip: Commit-ID: bf37da98c51825c90432d340e135cced37a7460d Gitweb: https://git.kernel.org/tip/bf37da98c51825c90432d340e135cced37a7460d Author: Paul E. McKenney AuthorDate: Thu, 12 Mar 2020 16:55:07 -07:00 Committer: Paul E. McKenney CommitterDate: Sun, 05 Apr 2020 14:22:15 -07:00 rcu: Don't acquire lock in NMI handler in rcu_nmi_enter_common() The rcu_nmi_enter_common() function can be invoked both in interrupt and NMI handlers. If it is invoked from process context (as opposed to userspace or idle context) on a nohz_full CPU, it might acquire the CPU's leaf rcu_node structure's ->lock. Because this lock is held only with interrupts disabled, this is safe from an interrupt handler, but doing so from an NMI handler can result in self-deadlock. This commit therefore adds "irq" to the "if" condition so as to only acquire the ->lock from irq handlers or process context, never from an NMI handler. Fixes: 5b14557b073c ("rcu: Avoid tick_dep_set_cpu() misordering") Reported-by: Thomas Gleixner Signed-off-by: Paul E. McKenney Reviewed-by: Joel Fernandes (Google) Cc: # 5.5.x --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 550193a..2c17859 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -825,7 +825,7 @@ static __always_inline void rcu_nmi_enter_common(bool irq) rcu_cleanup_after_idle(); incby = 1; - } else if (tick_nohz_full_cpu(rdp->cpu) && + } else if (irq && tick_nohz_full_cpu(rdp->cpu) && rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE && READ_ONCE(rdp->rcu_urgent_qs) && !READ_ONCE(rdp->rcu_forced_tick)) {