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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 95B2EC76195 for ; Fri, 19 Jul 2019 21:50:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7314921882 for ; Fri, 19 Jul 2019 21:50:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389181AbfGSVuy (ORCPT ); Fri, 19 Jul 2019 17:50:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:51138 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388771AbfGSVt7 (ORCPT ); Fri, 19 Jul 2019 17:49:59 -0400 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 93D06218A3; Fri, 19 Jul 2019 21:49:58 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.92) (envelope-from ) id 1hoalJ-00083g-N9; Fri, 19 Jul 2019 17:49:57 -0400 Message-Id: <20190719214957.604245348@goodmis.org> User-Agent: quilt/0.65 Date: Fri, 19 Jul 2019 17:49:41 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Paul Gortmaker , Julia Cartwright , Daniel Wagner , tom.zanussi@linux.intel.com Subject: [PATCH RT 10/16] Revert "futex: Fix bug on when a requeued RT task times out" References: <20190719214931.700049248@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.19.59-rt24-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior [ Upstream commit f1a170cb3289a48df26cae3c60d77608f7a988bb ] Drop the RT fixup, the futex code will be changed to avoid the need for the workaround. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- kernel/locking/rtmutex.c | 31 +------------------------------ kernel/locking/rtmutex_common.h | 1 - 2 files changed, 1 insertion(+), 31 deletions(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 2a9bf2443acc..7f6f402e04ae 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -144,8 +144,7 @@ static void fixup_rt_mutex_waiters(struct rt_mutex *lock) static int rt_mutex_real_waiter(struct rt_mutex_waiter *waiter) { - return waiter && waiter != PI_WAKEUP_INPROGRESS && - waiter != PI_REQUEUE_INPROGRESS; + return waiter && waiter != PI_WAKEUP_INPROGRESS; } /* @@ -2350,34 +2349,6 @@ int __rt_mutex_start_proxy_lock(struct rt_mutex *lock, if (try_to_take_rt_mutex(lock, task, NULL)) return 1; -#ifdef CONFIG_PREEMPT_RT_FULL - /* - * In PREEMPT_RT there's an added race. - * If the task, that we are about to requeue, times out, - * it can set the PI_WAKEUP_INPROGRESS. This tells the requeue - * to skip this task. But right after the task sets - * its pi_blocked_on to PI_WAKEUP_INPROGRESS it can then - * block on the spin_lock(&hb->lock), which in RT is an rtmutex. - * This will replace the PI_WAKEUP_INPROGRESS with the actual - * lock that it blocks on. We *must not* place this task - * on this proxy lock in that case. - * - * To prevent this race, we first take the task's pi_lock - * and check if it has updated its pi_blocked_on. If it has, - * we assume that it woke up and we return -EAGAIN. - * Otherwise, we set the task's pi_blocked_on to - * PI_REQUEUE_INPROGRESS, so that if the task is waking up - * it will know that we are in the process of requeuing it. - */ - raw_spin_lock(&task->pi_lock); - if (task->pi_blocked_on) { - raw_spin_unlock(&task->pi_lock); - return -EAGAIN; - } - task->pi_blocked_on = PI_REQUEUE_INPROGRESS; - raw_spin_unlock(&task->pi_lock); -#endif - /* We enforce deadlock detection for futexes */ ret = task_blocks_on_rt_mutex(lock, waiter, task, RT_MUTEX_FULL_CHAINWALK); diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 546aaf058b9e..a501f3b47081 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -133,7 +133,6 @@ enum rtmutex_chainwalk { * PI-futex support (proxy locking functions, etc.): */ #define PI_WAKEUP_INPROGRESS ((struct rt_mutex_waiter *) 1) -#define PI_REQUEUE_INPROGRESS ((struct rt_mutex_waiter *) 2) extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock); extern void rt_mutex_init_proxy_locked(struct rt_mutex *lock, -- 2.20.1