From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id BsQwE7KTGVtaTgAAmS7hNA ; Thu, 07 Jun 2018 20:22:11 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id AFEAC60452; Thu, 7 Jun 2018 20:22:11 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id F2840608B8; Thu, 7 Jun 2018 20:22:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org F2840608B8 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753614AbeFGUWI (ORCPT + 25 others); Thu, 7 Jun 2018 16:22:08 -0400 Received: from terminus.zytor.com ([198.137.202.136]:43105 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753028AbeFGUWH (ORCPT ); Thu, 7 Jun 2018 16:22:07 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w57KLwqn2320798 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Thu, 7 Jun 2018 13:21:58 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w57KLvcN2320795; Thu, 7 Jun 2018 13:21:57 -0700 Date: Thu, 7 Jun 2018 13:21:57 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Anna-Maria Gleixner Message-ID: Cc: mingo@kernel.org, ebiederm@xmission.com, bigeasy@linutronix.de, paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, anna-maria@linutronix.de, hpa@zytor.com Reply-To: anna-maria@linutronix.de, hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, ebiederm@xmission.com, bigeasy@linutronix.de, mingo@kernel.org In-Reply-To: <20180504144014.5378-1-bigeasy@linutronix.de> References: <20180504144014.5378-1-bigeasy@linutronix.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:core/urgent] signal: Remove no longer required irqsave/restore Git-Commit-ID: e79e0f38083e607da5d7b493e7a0f78ba38d788e X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: e79e0f38083e607da5d7b493e7a0f78ba38d788e Gitweb: https://git.kernel.org/tip/e79e0f38083e607da5d7b493e7a0f78ba38d788e Author: Anna-Maria Gleixner AuthorDate: Fri, 4 May 2018 16:40:14 +0200 Committer: Thomas Gleixner CommitDate: Thu, 7 Jun 2018 22:18:55 +0200 signal: Remove no longer required irqsave/restore Commit a841796f11c9 ("signal: align __lock_task_sighand() irq disabling and RCU") introduced a rcu read side critical section with interrupts disabled. The changelog suggested that a better long-term fix would be "to make rt_mutex_unlock() disable irqs when acquiring the rt_mutex structure's ->wait_lock". This long-term fix has been made in commit 4abf91047cf ("rtmutex: Make > wait_lock irq safe") for different reason. Therefore revert commit a841796f11c9 ("signal: align > __lock_task_sighand() irq disabling and RCU") as the interrupt disable dance is not longer required. Testing was done over an extensive period with RCU torture, especially with TREE03 as requested by Paul. Signed-off-by: Anna-Maria Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: "Paul E . McKenney" Acked-by: "Eric W. Biederman" Link: https://lkml.kernel.org/r/20180504144014.5378-1-bigeasy@linutronix.de --- kernel/signal.c | 24 +++++++----------------- 1 file changed, 7 insertions(+), 17 deletions(-) diff --git a/kernel/signal.c b/kernel/signal.c index 0f865d67415d..8d8a940422a8 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1244,19 +1244,12 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, { struct sighand_struct *sighand; + rcu_read_lock(); for (;;) { - /* - * Disable interrupts early to avoid deadlocks. - * See rcu_read_unlock() comment header for details. - */ - local_irq_save(*flags); - rcu_read_lock(); sighand = rcu_dereference(tsk->sighand); - if (unlikely(sighand == NULL)) { - rcu_read_unlock(); - local_irq_restore(*flags); + if (unlikely(sighand == NULL)) break; - } + /* * This sighand can be already freed and even reused, but * we rely on SLAB_TYPESAFE_BY_RCU and sighand_ctor() which @@ -1268,15 +1261,12 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, * __exit_signal(). In the latter case the next iteration * must see ->sighand == NULL. */ - spin_lock(&sighand->siglock); - if (likely(sighand == tsk->sighand)) { - rcu_read_unlock(); + spin_lock_irqsave(&sighand->siglock, *flags); + if (likely(sighand == tsk->sighand)) break; - } - spin_unlock(&sighand->siglock); - rcu_read_unlock(); - local_irq_restore(*flags); + spin_unlock_irqrestore(&sighand->siglock, *flags); } + rcu_read_unlock(); return sighand; }