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 93A96C2D0C3 for ; Mon, 16 Dec 2019 17:51:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 669272072B for ; Mon, 16 Dec 2019 17:51:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576518668; bh=lmNlI0Iy1U04FTtoVNG4GxPlCEQXl93btRPK0tuyk5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=x6lMv5eAtdiG674tiGr4zb4NQSnp42hZwthFvNCUq6be684ZRBfowFI3R+LT1dyNl UgIAaTdu+IZ5BlYDgV51RNG8/HKxMc20DA9810CDaEDOTYUDunXxp1C+U8pjlZZOE7 9dkF+Dnyz2Xz3ULrTWj6zr8uIaUM6qP2qS38JLVo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726742AbfLPRvH (ORCPT ); Mon, 16 Dec 2019 12:51:07 -0500 Received: from mail.kernel.org ([198.145.29.99]:40776 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726721AbfLPRvG (ORCPT ); Mon, 16 Dec 2019 12:51:06 -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 80ACE206EC; Mon, 16 Dec 2019 17:51:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576518666; bh=lmNlI0Iy1U04FTtoVNG4GxPlCEQXl93btRPK0tuyk5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QyXd5mAlTiy95I+vjSg4ZGpLs4zM9WM8L7ZKS4wvKCQbjuxM0kwEZnvyNRe7jfjM0 O8Gyh4hmWZ2yZGg7LpVE/wr221vmJutSDSbJBxa35pcH2pH8sLzE9VyXUAgpT6H+sy xEkM17QTrQhQq7bsOPr1ihHsYJAnevukUMSVRanE= 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 4.14 017/267] sched/core: Avoid spurious lock dependencies Date: Mon, 16 Dec 2019 18:45:43 +0100 Message-Id: <20191216174850.930105200@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20191216174848.701533383@linuxfoundation.org> References: <20191216174848.701533383@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 bbf8b32fc69ec..97a27726ea217 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5242,10 +5242,11 @@ 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