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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 45E17C433FF for ; Thu, 8 Aug 2019 19:54:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1955A2189F for ; Thu, 8 Aug 2019 19:54:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565294044; bh=yKvzDmOwoP6ZRaTvyr3khS9aKMHNufX4h05g7GeRnKY=; h=From:To:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=SSLO/J/lN8CaI5RKIN3NdS6BQZll5wVskbGvPxsL9i4pc2Kb1HY2CrGndLcWoR7ns SsKWrF3ARewwr2RBHE/BqpKM/nTnQ/ne6JWUEaV+XkmR456LCns+gtSFvPqCdKqG5B rlT+S9iTJZ6F/8PL4xf+dFo1pgV5a5PEW0tkQvq8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404530AbfHHTxY (ORCPT ); Thu, 8 Aug 2019 15:53:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:58088 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404501AbfHHTxX (ORCPT ); Thu, 8 Aug 2019 15:53:23 -0400 Received: from localhost.localdomain (c-98-220-238-81.hsd1.il.comcast.net [98.220.238.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3B6CA218CD; Thu, 8 Aug 2019 19:53:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565294002; bh=yKvzDmOwoP6ZRaTvyr3khS9aKMHNufX4h05g7GeRnKY=; h=From:To:Subject:Date:In-Reply-To:References:In-Reply-To: References:From; b=RhQHbrdmDul4X7nAkYO7dst2+4yNtmYeQkDgmzUMpAk76lA2Pnj04yGM5zUIAz+X8 yI2xSZNFlrVfIbBFtl7Okl5a1Xjcd6KTRKHxVmuBFPkZTLLDoafQaQxBfTCk9NmUqS 1eJYCjgiVW35aJBGtDtYRB15CfJptUB+bftknERY= From: zanussi@kernel.org To: LKML , linux-rt-users , Steven Rostedt , Thomas Gleixner , Carsten Emde , John Kacur , Sebastian Andrzej Siewior , Daniel Wagner , Tom Zanussi , Julia Cartwright Subject: [PATCH RT 13/19] Revert "futex: Fix bug on when a requeued RT task times out" Date: Thu, 8 Aug 2019 14:52:41 -0500 Message-Id: <050713a32b125bb79ad609c7de0de98fd52db92a.1565293934.git.zanussi@kernel.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org From: Sebastian Andrzej Siewior v4.14.137-rt65-rc1 stable review patch. If anyone has any objections, please let me know. ----------- [ 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: Tom Zanussi --- 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 1177f2815040..62914dde3f1c 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; } /* @@ -2358,34 +2357,6 @@ 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 2a157c78e18c..53ca0242101a 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -132,7 +132,6 @@ 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, -- 2.14.1