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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 34B80C4338F for ; Tue, 3 Aug 2021 16:12:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17DBD61029 for ; Tue, 3 Aug 2021 16:12:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232215AbhHCQMk (ORCPT ); Tue, 3 Aug 2021 12:12:40 -0400 Received: from foss.arm.com ([217.140.110.172]:51898 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231704AbhHCQMj (ORCPT ); Tue, 3 Aug 2021 12:12:39 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8B466139F; Tue, 3 Aug 2021 09:12:25 -0700 (PDT) Received: from e107158-lin.cambridge.arm.com (unknown [10.1.195.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 575243F66F; Tue, 3 Aug 2021 09:12:23 -0700 (PDT) Date: Tue, 3 Aug 2021 17:12:21 +0100 From: Qais Yousef To: "Paul E. McKenney" Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Yanfei Xu Subject: Re: [PATCH rcu 02/18] rcu: Fix stall-warning deadlock due to non-release of rcu_node ->lock Message-ID: <20210803161221.igae6y6xa6mlzltn@e107158-lin.cambridge.arm.com> References: <20210721202042.GA1472052@paulmck-ThinkPad-P17-Gen-1> <20210721202127.2129660-2-paulmck@kernel.org> <20210803142458.teveyn6t2gwifdcp@e107158-lin.cambridge.arm.com> <20210803155226.GQ4397@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210803155226.GQ4397@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/03/21 08:52, Paul E. McKenney wrote: > On Tue, Aug 03, 2021 at 03:24:58PM +0100, Qais Yousef wrote: > > Hi > > > > On 07/21/21 13:21, Paul E. McKenney wrote: > > > From: Yanfei Xu > > > > > > If rcu_print_task_stall() is invoked on an rcu_node structure that does > > > not contain any tasks blocking the current grace period, it takes an > > > early exit that fails to release that rcu_node structure's lock. This > > > results in a self-deadlock, which is detected by lockdep. > > > > > > To reproduce this bug: > > > > > > tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 3 --trust-make --configs "TREE03" --kconfig "CONFIG_PROVE_LOCKING=y" --bootargs "rcutorture.stall_cpu=30 rcutorture.stall_cpu_block=1 rcutorture.fwd_progress=0 rcutorture.test_boost=0" > > > > > > This will also result in other complaints, including RCU's scheduler > > > hook complaining about blocking rather than preemption and an rcutorture > > > writer stall. > > > > > > Only a partial RCU CPU stall warning message will be printed because of > > > the self-deadlock. > > > > > > This commit therefore releases the lock on the rcu_print_task_stall() > > > function's early exit path. > > > > > > Fixes: c583bcb8f5ed ("rcu: Don't invoke try_invoke_on_locked_down_task() with irqs disabled") > > > Signed-off-by: Yanfei Xu > > > Signed-off-by: Paul E. McKenney > > > --- > > > > We are seeing similar stall/deadlock issue on android 5.10 kernel, is the fix > > relevant here? Trying to apply the patches and test, but the problem is tricky > > to reproduce so thought worth asking first. > > Looks like the relevant symptoms to me, so I suggest trying this series > from -rcu: > > 8baded711edc ("rcu: Fix to include first blocked task in stall warning") > f6b3995a8b56 ("rcu: Fix stall-warning deadlock due to non-release of rcu_node ->lock") Great thanks. These are the ones we picked as the rest was a bit tricky to apply on 5.10. While at it, we see these errors too though they look harmless. They happen all the time [ 595.292685] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #02!!!"} [ 595.301467] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!"} [ 595.389353] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!"} [ 595.397454] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!"} [ 595.417112] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!"} [ 595.425215] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!"} [ 595.438807] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!"} I used to see them on mainline a while back but seem to have been fixed. Something didn't get backported to 5.10 perhaps? It might be a question to Frederic actually.. Thanks! -- Qais Yousef