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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 AEAC8C43387 for ; Fri, 21 Dec 2018 15:21:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A16321939 for ; Fri, 21 Dec 2018 15:21:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545405704; bh=+GUFcob1zAnoT5TEMD1SMg3L8/OrWZJKRXajWl2SOUM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:List-ID:From; b=sGxbz4GeujIjT10pZ+JUyLnw3ellTYDuLVYJ4cWIjbWJ1Rt0zjleyAv5IQ1ps6ehF pZFuk2lGA2B46L4ANXL2c7yJx/i8GWFaiduot/JJaHm4oLAztefoOKzxfG8nzCgP2R bk9QCALBnsPkFu9yGpYuSzq0IRi5pVvAju3lI5RE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404191AbeLUPVn (ORCPT ); Fri, 21 Dec 2018 10:21:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:57128 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404164AbeLUPVh (ORCPT ); Fri, 21 Dec 2018 10:21:37 -0500 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 D731321929; Fri, 21 Dec 2018 15:21:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1545405696; bh=+GUFcob1zAnoT5TEMD1SMg3L8/OrWZJKRXajWl2SOUM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:In-Reply-To: References:From; b=Z1aLoUcikioTJvMG7l1oqdQC3NoU0rQ7SWulJZQCV3D4dkKiANGL1Uy1el0q4z6wS pIsceTZ/0RK385w4YEhDMj9kW7f1h6I9q+xAPRIZo0/4kRNGtNFFCHv11AI0ngjlmU Nd9E/QxTleKfiC0DnnzhFCZxHkVgolYknibGLfHw= From: Tom Zanussi To: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Cc: rostedt@goodmis.org, tglx@linutronix.de, C.Emde@osadl.org, jkacur@redhat.com, bigeasy@linutronix.de, daniel.wagner@siemens.com, julia@ni.com Subject: [PATCH RT 4/9] sched/core: Avoid __schedule() being called twice in a row Date: Fri, 21 Dec 2018 09:21:16 -0600 Message-Id: X-Mailer: git-send-email 2.14.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org v3.18.129-rt111 rt-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 [bigeasy: rewrite changelog] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Tom Zanussi --- 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 d5534f439b4a..500c319fcfc5 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3114,10 +3114,15 @@ 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; -- 2.14.1