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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 3FA13C433F5 for ; Wed, 5 Sep 2018 12:29:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E66BD20861 for ; Wed, 5 Sep 2018 12:29:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E66BD20861 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728046AbeIEQ7Y (ORCPT ); Wed, 5 Sep 2018 12:59:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:47214 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727792AbeIEQ6k (ORCPT ); Wed, 5 Sep 2018 12:58:40 -0400 Received: from gandalf.local.home (cpe-66-24-56-78.stny.res.rr.com [66.24.56.78]) (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 53B6A2087F; Wed, 5 Sep 2018 12:28:38 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.91) (envelope-from ) id 1fxWvF-0002F9-BA; Wed, 05 Sep 2018 08:28:37 -0400 Message-Id: <20180905122837.239092225@goodmis.org> User-Agent: quilt/0.65 Date: Wed, 05 Sep 2018 08:28:12 -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, Daniel Bristot de Oliveira , Clark Williams , Tommaso Cucinotta , Romulo da Silva de Oliveira , Ingo Molnar , Peter Zijlstra Subject: [PATCH RT 18/22] sched/core: Avoid __schedule() being called twice in a row References: <20180905122754.443196118@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 4.14.63-rt41-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Bristot de Oliveira [ Upstream commit 2bb94c48b2ffaabf8c15a51e5cc1b4c541988cab ] If a worker invokes schedule() then we may have the call chain: schedule() -> sched_submit_work() -> wq_worker_sleeping() -> wake_up_worker() -> wake_up_process(). The last wakeup may cause a schedule which is unnecessary because we are already in schedule() and do it anyway. Add a preempt_disable() + preempt_enable_no_resched() around wq_worker_sleeping() so the context switch could be delayed until __schedule(). Signed-off-by: Daniel Bristot de Oliveira Cc: Clark Williams Cc: Tommaso Cucinotta Cc: Romulo da Silva de Oliveira Cc: Sebastian Andrzej Siewior Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Steven Rostedt (VMware) [bigeasy: rewrite changelog] Signed-off-by: Sebastian Andrzej Siewior --- kernel/sched/core.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fa5b76255f8c..a5ce37b90fca 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3482,10 +3482,15 @@ static inline void sched_submit_work(struct task_struct *tsk) /* * If a worker went to sleep, notify and ask workqueue whether * it wants to wake up a task to maintain concurrency. + * As this function is called inside the schedule() context, + * we disable preemption to avoid it calling schedule() again + * in the possible wakeup of a kworker. */ - if (tsk->flags & PF_WQ_WORKER) + if (tsk->flags & PF_WQ_WORKER) { + preempt_disable(); wq_worker_sleeping(tsk); - + preempt_enable_no_resched(); + } if (tsk_is_pi_blocked(tsk)) return; -- 2.18.0