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,URIBL_BLOCKED,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 CCB65C43603 for ; Wed, 11 Dec 2019 15:16:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F70922B48 for ; Wed, 11 Dec 2019 15:16:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576077389; bh=kBjnG/eZkeii9sVMHiGtkUajug7tvFEukRI603lJuxo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=yb6lu6HBGENFNhHbF9pCulOQ/AELJkkUv2jHl9J8hp+krSYO/hODFVsujoX631vVb Mfy8sapTR4b/G1Zuph5QJd6KBaG+tpURE4iJkR1yetSyu9TOOvJPQJCChqbIShSYN5 nznhtGv4//eqlnP08HMnmTaAfGhSTDN7KYcv8Y98= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730889AbfLKPQ2 (ORCPT ); Wed, 11 Dec 2019 10:16:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:43452 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731892AbfLKPQX (ORCPT ); Wed, 11 Dec 2019 10:16:23 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 F0BB52465C; Wed, 11 Dec 2019 15:16:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576077383; bh=kBjnG/eZkeii9sVMHiGtkUajug7tvFEukRI603lJuxo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CBDB9yG/NC3dKH74QiaAr88DK2CKmrhJWlWw0ZrCgn+um7Q+OwF99fIwuCeqt7mCx MYiPyaylyXal2zR4h2YsK4MyI1xHyc6/iSDgO1ckcsV1X2Jxv8gcCVdDOVTqleIZV8 OS8TjgPGfnqxem7MCyYDqMr8oBJw49y3GLX9L4Lo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "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 , Sasha Levin Subject: [PATCH 4.19 019/243] sched/core: Avoid spurious lock dependencies Date: Wed, 11 Dec 2019 16:03:01 +0100 Message-Id: <20191211150340.289643678@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191211150339.185439726@linuxfoundation.org> References: <20191211150339.185439726@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra [ Upstream commit ff51ff84d82aea5a889b85f2b9fb3aa2b8691668 ] 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 Signed-off-by: Sasha Levin --- 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 78ecdfae25b69..2befd2c4ce9e6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5413,10 +5413,11 @@ 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; -- 2.20.1