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=-15.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PULL_REQUEST,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 75AFEC388F9 for ; Mon, 16 Nov 2020 22:01:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 14CBA20756 for ; Mon, 16 Nov 2020 22:01:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="cr5uP2Ak" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730655AbgKPWBy (ORCPT ); Mon, 16 Nov 2020 17:01:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:44542 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730558AbgKPWBx (ORCPT ); Mon, 16 Nov 2020 17:01:53 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (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 614DE20729; Mon, 16 Nov 2020 22:01:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605564113; bh=7Cwv1bYHbUQxsXyRFNkvF6kCBu8xgcspou1Dr4dTpK0=; h=Date:From:To:Cc:Subject:Reply-To:From; b=cr5uP2Akdb7peDlKRhNy5bfy+aPlUu8O2ulpHZ3rs9KQkEFh/aHMyPWZHOU7XLfkk U1ZPqcs1PoSMECk5Xp8ZayGbZTgYMgCCA/OVUgWt1c9v0Nk5oMLLs/Vyx3QCpQfOFN LdvovBlmxeOWSacf+ikW0ixafiINylKIqoyM5ZpU= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 143693522684; Mon, 16 Nov 2020 14:01:53 -0800 (PST) Date: Mon, 16 Nov 2020 14:01:53 -0800 From: "Paul E. McKenney" To: torvalds@linux-foundation.org Cc: tglx@linutronix.de, mingo@redhat.com, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, kernel-team@fb.com, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, bigeasy@linutronix.de Subject: [GIT RFC PULL rcu/urgent] Fix lockdep issue in rcu_print_task_stall() Message-ID: <20201116220153.GA22623@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! This pull request contains a single commit that fixes a bug that was introduced a couple of merge windows ago, but which rather more recently converged to an agreed-upon fix. The bug is that interrupts can be incorrectly enabled while holding an irq-disabled spinlock. This can of course result in self-deadlocks. The bug is a bit difficult to trigger. It requires that a preempted task be blocking a preemptible-RCU grace period long enough to trigger an RCU CPU stall warning. In addition, an interrupt must occur at just the right time, and that interrupt's handler must acquire that same irq-disabled spinlock. Still, a deadlock is a deadlock. Furthermore, we do now have a fix, and that fix survives kernel test robot, -next, and rcutorture testing. It has also been verified by Sebastian as fixing the bug. Therefore... The following changes since commit 3650b228f83adda7e5ee532e2b90429c03f7b9ec: Linux 5.10-rc1 (2020-10-25 15:14:11 -0700) are available in the git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git urgent-fixes for you to fetch changes up to c583bcb8f5edd48c1798798e341f78afb9bf4f6f: rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled (2020-11-10 17:10:38 -0800) ---------------------------------------------------------------- Paul E. McKenney (1): rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled kernel/rcu/tree_stall.h | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-)