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=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,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 793B0C17442 for ; Wed, 13 Nov 2019 10:06:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5B9CF2245A for ; Wed, 13 Nov 2019 10:06:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727362AbfKMKGm (ORCPT ); Wed, 13 Nov 2019 05:06:42 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:37159 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726338AbfKMKGk (ORCPT ); Wed, 13 Nov 2019 05:06:40 -0500 Received: from [5.158.153.53] (helo=tip-bot2.lab.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iUpXh-0000LE-Ib; Wed, 13 Nov 2019 11:06:29 +0100 Received: from [127.0.1.1] (localhost [IPv6:::1]) by tip-bot2.lab.linutronix.de (Postfix) with ESMTP id 3CC681C0092; Wed, 13 Nov 2019 11:06:29 +0100 (CET) Date: Wed, 13 Nov 2019 10:06:28 -0000 From: "tip-bot2 for Peter Zijlstra" Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/urgent] sched/core: Avoid spurious lock dependencies Cc: "Peter Zijlstra (Intel)" , Linus Torvalds , Qian Cai , Thomas Gleixner , akpm@linux-foundation.org, bigeasy@linutronix.de, cl@linux.com, keescook@chromium.org, penberg@kernel.org, rientjes@google.com, thgarnie@google.com, tytso@mit.edu, will@kernel.org, Ingo Molnar , Borislav Petkov , linux-kernel@vger.kernel.org In-Reply-To: <20191001091837.GK4536@hirez.programming.kicks-ass.net> References: <20191001091837.GK4536@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Message-ID: <157363958888.29376.9190587096871610849.tip-bot2@tip-bot2> X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/urgent branch of tip: Commit-ID: ff51ff84d82aea5a889b85f2b9fb3aa2b8691668 Gitweb: https://git.kernel.org/tip/ff51ff84d82aea5a889b85f2b9fb3aa2b8691668 Author: Peter Zijlstra AuthorDate: Tue, 01 Oct 2019 11:18:37 +02:00 Committer: Ingo Molnar CommitterDate: Wed, 13 Nov 2019 08:01:30 +01:00 sched/core: Avoid spurious lock dependencies While seemingly harmless, __sched_fork() does hrtimer_init(), which, when DEBUG_OBJETS, can end up doing allocations. This then results in the following lock order: rq->lock zone->lock.rlock batched_entropy_u64.lock Which in turn causes deadlocks when we do wakeups while holding that batched_entropy lock -- as the random code does. Solve this by moving __sched_fork() out from under rq->lock. This is safe because nothing there relies on rq->lock, as also evident from the other __sched_fork() callsite. Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Qian Cai Cc: Thomas Gleixner Cc: akpm@linux-foundation.org Cc: bigeasy@linutronix.de Cc: cl@linux.com Cc: keescook@chromium.org Cc: penberg@kernel.org Cc: rientjes@google.com Cc: thgarnie@google.com Cc: tytso@mit.edu Cc: will@kernel.org Fixes: b7d5dc21072c ("random: add a spinlock_t to struct batched_entropy") Link: https://lkml.kernel.org/r/20191001091837.GK4536@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0f2eb36..33cd250 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6019,10 +6019,11 @@ void init_idle(struct task_struct *idle, int cpu) struct rq *rq = cpu_rq(cpu); unsigned long flags; + __sched_fork(0, idle); + raw_spin_lock_irqsave(&idle->pi_lock, flags); raw_spin_lock(&rq->lock); - __sched_fork(0, idle); idle->state = TASK_RUNNING; idle->se.exec_start = sched_clock(); idle->flags |= PF_IDLE;