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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 4FC34C2D0DB for ; Thu, 23 Jan 2020 20:41:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 27E4224691 for ; Thu, 23 Jan 2020 20:41:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729719AbgAWUlB (ORCPT ); Thu, 23 Jan 2020 15:41:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:45944 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729306AbgAWUjr (ORCPT ); Thu, 23 Jan 2020 15:39:47 -0500 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 35F292468B; Thu, 23 Jan 2020 20:39:46 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.93) (envelope-from ) id 1iujGT-000mdD-4Y; Thu, 23 Jan 2020 15:39:45 -0500 Message-Id: <20200123203945.023629945@goodmis.org> User-Agent: quilt/0.65 Date: Thu, 23 Jan 2020 15:39:49 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Julia Cartwright , Daniel Wagner , Tom Zanussi , "Peter Zijlstra (Intel)" Subject: [PATCH RT 19/30] locking/rtmutex: Clean ->pi_blocked_on in the error case References: <20200123203930.646725253@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 4.19.94-rt39-rc2 stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra [ Upstream commit 0be4ea6e3ce693101be0fbd55a0cc7ce238ab2eb ] The function rt_mutex_wait_proxy_lock() cleans ->pi_blocked_on in case of failure (timeout, signal). The same cleanup is required in __rt_mutex_start_proxy_lock(). In both the cases the tasks was interrupted by a signal or timeout while acquiring the lock and after the interruption it longer blocks on the lock. Fixes: 1a1fb985f2e2b ("futex: Handle early deadlock return correctly") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- kernel/locking/rtmutex.c | 43 +++++++++++++++++++++++----------------- 1 file changed, 25 insertions(+), 18 deletions(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 2a9bf2443acc..63b3d6f306fa 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -2320,6 +2320,26 @@ void rt_mutex_proxy_unlock(struct rt_mutex *lock, rt_mutex_set_owner(lock, NULL); } +static void fixup_rt_mutex_blocked(struct rt_mutex *lock) +{ + struct task_struct *tsk = current; + /* + * RT has a problem here when the wait got interrupted by a timeout + * or a signal. task->pi_blocked_on is still set. The task must + * acquire the hash bucket lock when returning from this function. + * + * If the hash bucket lock is contended then the + * BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in + * task_blocks_on_rt_mutex() will trigger. This can be avoided by + * clearing task->pi_blocked_on which removes the task from the + * boosting chain of the rtmutex. That's correct because the task + * is not longer blocked on it. + */ + raw_spin_lock(&tsk->pi_lock); + tsk->pi_blocked_on = NULL; + raw_spin_unlock(&tsk->pi_lock); +} + /** * __rt_mutex_start_proxy_lock() - Start lock acquisition for another task * @lock: the rt_mutex to take @@ -2392,6 +2412,9 @@ int __rt_mutex_start_proxy_lock(struct rt_mutex *lock, ret = 0; } + if (ret) + fixup_rt_mutex_blocked(lock); + debug_rt_mutex_print_deadlock(waiter); return ret; @@ -2472,7 +2495,6 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock, struct hrtimer_sleeper *to, struct rt_mutex_waiter *waiter) { - struct task_struct *tsk = current; int ret; raw_spin_lock_irq(&lock->wait_lock); @@ -2484,23 +2506,8 @@ int rt_mutex_wait_proxy_lock(struct rt_mutex *lock, * have to fix that up. */ fixup_rt_mutex_waiters(lock); - /* - * RT has a problem here when the wait got interrupted by a timeout - * or a signal. task->pi_blocked_on is still set. The task must - * acquire the hash bucket lock when returning from this function. - * - * If the hash bucket lock is contended then the - * BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in - * task_blocks_on_rt_mutex() will trigger. This can be avoided by - * clearing task->pi_blocked_on which removes the task from the - * boosting chain of the rtmutex. That's correct because the task - * is not longer blocked on it. - */ - if (ret) { - raw_spin_lock(&tsk->pi_lock); - tsk->pi_blocked_on = NULL; - raw_spin_unlock(&tsk->pi_lock); - } + if (ret) + fixup_rt_mutex_blocked(lock); raw_spin_unlock_irq(&lock->wait_lock); -- 2.24.1