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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 AE075C433EF for ; Sun, 8 Sep 2019 12:51:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 89A95218AC for ; Sun, 8 Sep 2019 12:51:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567947104; bh=gZVmyGNN3awcb8D19eauWMRQw0XXcTPKXUb62OgyKc0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=fGu/HdRoFrFZDIuvV4bOO51fSPstqgbjpjf92Dp02vmDHxWy3r20mT9O7DA53/YnA iNhIaYXAvdenBQnAB6RrHTuQ28oFceSQjeBbx82j8di4pcFbULBSXilg6HaIoQxHau fxLS3PC1Uwx39C6GzOwZfSAG6NGfNYcipvcxDKs8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732742AbfIHMvn (ORCPT ); Sun, 8 Sep 2019 08:51:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:43412 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732675AbfIHMvn (ORCPT ); Sun, 8 Sep 2019 08:51:43 -0400 Received: from localhost (unknown [62.28.240.114]) (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 28EAE20693; Sun, 8 Sep 2019 12:51:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567947102; bh=gZVmyGNN3awcb8D19eauWMRQw0XXcTPKXUb62OgyKc0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PVWoal+aRtJZIPF2BcyEmLMazuQrR05pQy5SSz04FpN7zuqLjGqpD1PVgGUAlT3lt DrIUlvtqEuC0+7h3rcrzeSBC/EeAyx5z076nRzh/I6Q8cCAyE3CfzAwv382m1fOMgP JI4zCHcaMco44LzMw75VlurWGb/MsBCV4oWbcQF8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sebastian Andrzej Siewior , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH 5.2 63/94] sched/core: Schedule new worker even if PI-blocked Date: Sun, 8 Sep 2019 13:41:59 +0100 Message-Id: <20190908121152.237568541@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190908121150.420989666@linuxfoundation.org> References: <20190908121150.420989666@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org [ Upstream commit b0fdc01354f45d43f082025636ef808968a27b36 ] If a task is PI-blocked (blocking on sleeping spinlock) then we don't want to schedule a new kworker if we schedule out due to lock contention because !RT does not do that as well. A spinning spinlock disables preemption and a worker does not schedule out on lock contention (but spin). On RT the RW-semaphore implementation uses an rtmutex so tsk_is_pi_blocked() will return true if a task blocks on it. In this case we will now start a new worker which may deadlock if one worker is waiting on progress from another worker. Since a RW-semaphore starts a new worker on !RT, we should do the same on RT. XFS is able to trigger this deadlock. Allow to schedule new worker if the current worker is PI-blocked. Signed-off-by: Sebastian Andrzej Siewior Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20190816160626.12742-1-bigeasy@linutronix.de Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/core.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4d5962232a553..42bc2986520d7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3469,7 +3469,7 @@ void __noreturn do_task_dead(void) static inline void sched_submit_work(struct task_struct *tsk) { - if (!tsk->state || tsk_is_pi_blocked(tsk)) + if (!tsk->state) return; /* @@ -3485,6 +3485,9 @@ static inline void sched_submit_work(struct task_struct *tsk) preempt_enable_no_resched(); } + if (tsk_is_pi_blocked(tsk)) + return; + /* * If we are going to sleep and we have plugged IO queued, * make sure to submit it to avoid deadlocks. -- 2.20.1