From patchwork Fri Jul 9 13:18:34 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 472300 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT 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 F197AC11F67 for ; Fri, 9 Jul 2021 13:19:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD1B4613C5 for ; Fri, 9 Jul 2021 13:19:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231976AbhGINVm (ORCPT ); Fri, 9 Jul 2021 09:21:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:51918 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232021AbhGINVl (ORCPT ); Fri, 9 Jul 2021 09:21:41 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E82AF61357; Fri, 9 Jul 2021 13:18:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1625836738; bh=aNIfBMAS+OUJJ23eapl/YTXCKRYtQWg8KfJDh4UNTkY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HN8noom+uIbU1YHnuipGBIwnDRy9YTQTRecRZFP8FJcihOsSemuXXTYt9Sztn3MUN /kz7cuFVgzMG/XcVI23MRMz7f4/OSC2x1ykCf59b2oFYTQc2uEeNf3+a32oxUkW51R PVNgM0dUhP5DmPhAUc0nSEVKJ06e08LpojkiLDoM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Petr Mladek , jenhaochen@google.com, Martin Liu , Minchan Kim , Nathan Chancellor , Nick Desaulniers , Oleg Nesterov , Tejun Heo , Andrew Morton , Linus Torvalds Subject: [PATCH 4.9 7/9] kthread_worker: split code for canceling the delayed work timer Date: Fri, 9 Jul 2021 15:18:34 +0200 Message-Id: <20210709131552.455038494@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210709131542.410636747@linuxfoundation.org> References: <20210709131542.410636747@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Petr Mladek commit 34b3d5344719d14fd2185b2d9459b3abcb8cf9d8 upstream. Patch series "kthread_worker: Fix race between kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync()". This patchset fixes the race between kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync() including proper return value handling. This patch (of 2): Simple code refactoring as a preparation step for fixing a race between kthread_mod_delayed_work() and kthread_cancel_delayed_work_sync(). It does not modify the existing behavior. Link: https://lkml.kernel.org/r/20210610133051.15337-2-pmladek@suse.com Signed-off-by: Petr Mladek Cc: Cc: Martin Liu Cc: Minchan Kim Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Oleg Nesterov Cc: Tejun Heo Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/kthread.c | 46 +++++++++++++++++++++++++++++----------------- 1 file changed, 29 insertions(+), 17 deletions(-) --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -952,6 +952,33 @@ void kthread_flush_work(struct kthread_w EXPORT_SYMBOL_GPL(kthread_flush_work); /* + * Make sure that the timer is neither set nor running and could + * not manipulate the work list_head any longer. + * + * The function is called under worker->lock. The lock is temporary + * released but the timer can't be set again in the meantime. + */ +static void kthread_cancel_delayed_work_timer(struct kthread_work *work, + unsigned long *flags) +{ + struct kthread_delayed_work *dwork = + container_of(work, struct kthread_delayed_work, work); + struct kthread_worker *worker = work->worker; + + /* + * del_timer_sync() must be called to make sure that the timer + * callback is not running. The lock must be temporary released + * to avoid a deadlock with the callback. In the meantime, + * any queuing is blocked by setting the canceling counter. + */ + work->canceling++; + spin_unlock_irqrestore(&worker->lock, *flags); + del_timer_sync(&dwork->timer); + spin_lock_irqsave(&worker->lock, *flags); + work->canceling--; +} + +/* * This function removes the work from the worker queue. Also it makes sure * that it won't get queued later via the delayed work's timer. * @@ -965,23 +992,8 @@ static bool __kthread_cancel_work(struct unsigned long *flags) { /* Try to cancel the timer if exists. */ - if (is_dwork) { - struct kthread_delayed_work *dwork = - container_of(work, struct kthread_delayed_work, work); - struct kthread_worker *worker = work->worker; - - /* - * del_timer_sync() must be called to make sure that the timer - * callback is not running. The lock must be temporary released - * to avoid a deadlock with the callback. In the meantime, - * any queuing is blocked by setting the canceling counter. - */ - work->canceling++; - spin_unlock_irqrestore(&worker->lock, *flags); - del_timer_sync(&dwork->timer); - spin_lock_irqsave(&worker->lock, *flags); - work->canceling--; - } + if (is_dwork) + kthread_cancel_delayed_work_timer(work, flags); /* * Try to remove the work from a worker list. It might either