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=-11.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C3151C3A59D for ; Mon, 19 Aug 2019 09:53:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 941DC2184D for ; Mon, 19 Aug 2019 09:53:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="f7t2xJBY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727250AbfHSJxI (ORCPT ); Mon, 19 Aug 2019 05:53:08 -0400 Received: from terminus.zytor.com ([198.137.202.136]:48991 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726366AbfHSJxH (ORCPT ); Mon, 19 Aug 2019 05:53:07 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x7J9qwAL4086401 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Mon, 19 Aug 2019 02:52:58 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 terminus.zytor.com x7J9qwAL4086401 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2019071901; t=1566208379; bh=ViFhlYlb4mbXvgvShCwnzSPVgUnY402sGO27DQuiJyc=; h=Date:From:Cc:Reply-To:In-Reply-To:References:To:Subject:From; b=f7t2xJBYGTifbTouaeiJWIetLKpUdTGgk2bMt04z3zFhLpBueNJ8FsrAk/NA+WWSA 1gWL4dIIemWQOHo42krbfrFe31s4aw9QK8qZrVVoi2rkeYsf2e3km32oq4JPX1ThfI RivjZsyQCfgx0GcSN8frd7EMRAoPdtw1scToKhk4o2Y3MXfOKkkSmWC24lexp3GJLQ 4zuvVe11/6lX62AHdFitbn2jCRCaTP4U5j9FpRU6/zXq3im3VT+jzQZ0YPLcNxjq8Z 3IuDIla9fWACi6tglaBOn5Rem7jFYrDj4WgLfNFCGiMBfKj3gbFCjXbcwXiBsfT0tc iOaz1DeCODkRw== Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x7J9qwCj4086398; Mon, 19 Aug 2019 02:52:58 -0700 Date: Mon, 19 Aug 2019 02:52:58 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Sebastian Andrzej Siewior Message-ID: Cc: hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, bigeasy@linutronix.de, mingo@kernel.org Reply-To: peterz@infradead.org, bigeasy@linutronix.de, linux-kernel@vger.kernel.org, tglx@linutronix.de, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org In-Reply-To: <20190816160626.12742-1-bigeasy@linutronix.de> References: <20190816160626.12742-1-bigeasy@linutronix.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/core: Schedule new worker even if PI-blocked Git-Commit-ID: b0fdc01354f45d43f082025636ef808968a27b36 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: b0fdc01354f45d43f082025636ef808968a27b36 Gitweb: https://git.kernel.org/tip/b0fdc01354f45d43f082025636ef808968a27b36 Author: Sebastian Andrzej Siewior AuthorDate: Fri, 16 Aug 2019 18:06:26 +0200 Committer: Ingo Molnar CommitDate: Mon, 19 Aug 2019 10:57:26 +0200 sched/core: Schedule new worker even if PI-blocked 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 --- 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 2b037f195473..010d578118d6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3904,7 +3904,7 @@ 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; /* @@ -3920,6 +3920,9 @@ 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.