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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 49C38C3815B for ; Mon, 20 Apr 2020 12:55:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C35C206D5 for ; Mon, 20 Apr 2020 12:55:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587387328; bh=HBAym8ekahvMlEeslnbCh2FaaepabcjHWf4jPxOqKYI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=RyfI33sphHAnSNZ+g4zvz/fILSVqr8phx6JSG9tpRXSft/Kpb9eTh0Ex3whHbwiHp 3fssloI6/CFR5Kg9W9g02Cj+7I/LwbpNe6rQsK1M2H9e7rS9X7kT3l3p7ONMuBkn72 an3SY3PRKDjrkS82RVHoQ2npe+k1EdHOBMUEm09E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728815AbgDTMpo (ORCPT ); Mon, 20 Apr 2020 08:45:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:40502 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728784AbgDTMpj (ORCPT ); Mon, 20 Apr 2020 08:45:39 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 14210206DD; Mon, 20 Apr 2020 12:45:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587386738; bh=HBAym8ekahvMlEeslnbCh2FaaepabcjHWf4jPxOqKYI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yLFDyL805/K0OlHz1Im6XsPlIdFF6+BkDAJPv0pQpYpZAW1j5vAwBq8ym4jurn6Ce uPtItv4M+X1zJF9VfXRx7VrxWN1g4w9GO20OPqMq0qg/3AoXeXx77Ec8O8GkuuYv7K Q1Pfol9oiKc1fj5TZN2Mk2XL0ztrJAu8H1pW/cnw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Gleixner , "Paul E. McKenney" , "Joel Fernandes (Google)" Subject: [PATCH 5.6 64/71] rcu: Dont acquire lock in NMI handler in rcu_nmi_enter_common() Date: Mon, 20 Apr 2020 14:39:18 +0200 Message-Id: <20200420121521.714417792@linuxfoundation.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200420121508.491252919@linuxfoundation.org> References: <20200420121508.491252919@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paul E. McKenney commit bf37da98c51825c90432d340e135cced37a7460d upstream. 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 Signed-off-by: Greg Kroah-Hartman --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -816,7 +816,7 @@ static __always_inline void rcu_nmi_ente 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) && !rdp->rcu_forced_tick) { raw_spin_lock_rcu_node(rdp->mynode);