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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 72FB4C432C0 for ; Fri, 22 Nov 2019 19:49:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4961F207DD for ; Fri, 22 Nov 2019 19:49:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574452157; bh=kBjnG/eZkeii9sVMHiGtkUajug7tvFEukRI603lJuxo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=poJnCDE3JEiad/WRp3ouB25POjig/aIxWMmBlWzRjBLyhszAatcITFYr35ApJyctY D2R1mqHlzgtiAz930IpaS5Bve4p/6+N5Tkb+H3wtl02r2j5qy/52hDO45bTl3PVnwi DdQSWv8wlEm8p1Oy9pzAKz7yZNoItLYdy+E96z7Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727270AbfKVTtP (ORCPT ); Fri, 22 Nov 2019 14:49:15 -0500 Received: from mail.kernel.org ([198.145.29.99]:48340 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727212AbfKVTtM (ORCPT ); Fri, 22 Nov 2019 14:49:12 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2C7892075E; Fri, 22 Nov 2019 19:49:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574452151; bh=kBjnG/eZkeii9sVMHiGtkUajug7tvFEukRI603lJuxo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c1xOk05AuU2xuggQHD5DVlKwBlHc+NTFbDMTnzfnO96HUS7hbtJVSss+TPuoxYEoy 3vwlpc+vB/qcdcUIDzxihPBUDxe3d2ff+rwHyJ0pLfvA4Wyc5E6vfRq/wkZoAIPM2Y 5XF5MrUEE+NoYHZXeEgv+DJjLaD8YSZLrljQNDtw= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Peter Zijlstra , 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 AUTOSEL 4.19 10/25] sched/core: Avoid spurious lock dependencies Date: Fri, 22 Nov 2019 14:48:43 -0500 Message-Id: <20191122194859.24508-10-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191122194859.24508-1-sashal@kernel.org> References: <20191122194859.24508-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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