From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33642 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730002AbeIMTCp (ORCPT ); Thu, 13 Sep 2018 15:02:45 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Johannes Berg , Tejun Heo , Sasha Levin Subject: [PATCH 4.18 050/197] workqueue: re-add lockdep dependencies for flushing Date: Thu, 13 Sep 2018 15:29:59 +0200 Message-Id: <20180913131843.539392943@linuxfoundation.org> In-Reply-To: <20180913131841.568116777@linuxfoundation.org> References: <20180913131841.568116777@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johannes Berg [ Upstream commit 87915adc3f0acdf03c776df42e308e5a155c19af ] In flush_work(), we need to create a lockdep dependency so that the following scenario is appropriately tagged as a problem: work_function() { mutex_lock(&mutex); ... } other_function() { mutex_lock(&mutex); flush_work(&work); // or cancel_work_sync(&work); } This is a problem since the work might be running and be blocked on trying to acquire the mutex. Similarly, in flush_workqueue(). These were removed after cross-release partially caught these problems, but now cross-release was reverted anyway. IMHO the removal was erroneous anyway though, since lockdep should be able to catch potential problems, not just actual ones, and cross-release would only have caught the problem when actually invoking wait_for_completion(). Fixes: fd1a5b04dfb8 ("workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes") Signed-off-by: Johannes Berg Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- kernel/workqueue.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2652,6 +2652,9 @@ void flush_workqueue(struct workqueue_st if (WARN_ON(!wq_online)) return; + lock_map_acquire(&wq->lockdep_map); + lock_map_release(&wq->lockdep_map); + mutex_lock(&wq->mutex); /* @@ -2905,6 +2908,11 @@ static bool __flush_work(struct work_str if (WARN_ON(!wq_online)) return false; + if (!from_cancel) { + lock_map_acquire(&work->lockdep_map); + lock_map_release(&work->lockdep_map); + } + if (start_flush_work(work, &barr, from_cancel)) { wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work);