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=-11.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 33C28C4338F for ; Tue, 3 Aug 2021 15:52:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 130BF60F93 for ; Tue, 3 Aug 2021 15:52:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237076AbhHCPwj (ORCPT ); Tue, 3 Aug 2021 11:52:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:47530 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237050AbhHCPwi (ORCPT ); Tue, 3 Aug 2021 11:52:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CBB5860EE8; Tue, 3 Aug 2021 15:52:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1628005946; bh=i7hDjTR9h/oiAZYkg8AT4x1Ck7tSiz+tHAzh0re3f2w=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=JSSEnCKReSKp1IrYRMZgcvkUGC3F4Ev3olZKIfLBogoro5DnCwMdmDv4s9OhKwiFO xqokdeOCS2CQYnYyCo3fnLihoGQEF3pCAj7CJcx1sjGxCg5Q8DXQbybFGcFCkB1eXK oH2Si/2833mXqvMB3QLFtu4EHgI2ECJMyL/QgnUfr5cIX6hmfj1iPnmGk9xZbaj1oI if73z6EyJ5nBeoBaJiJu9fY9j/hUue2rSS7T/5PuURuq6pM5QmnZ4l5sSfyDSdEZiH aRQTHk8seVtBdnNx3DndS2/g6w/hNX73ihWw7tkIqzLFZYI1AZjibLvyL3QrZU31ba Rt2b6rvR8kCuA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 93E8B5C04D4; Tue, 3 Aug 2021 08:52:26 -0700 (PDT) Date: Tue, 3 Aug 2021 08:52:26 -0700 From: "Paul E. McKenney" To: Qais Yousef 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: <20210803155226.GQ4397@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210721202042.GA1472052@paulmck-ThinkPad-P17-Gen-1> <20210721202127.2129660-2-paulmck@kernel.org> <20210803142458.teveyn6t2gwifdcp@e107158-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210803142458.teveyn6t2gwifdcp@e107158-lin.cambridge.arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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") Thanx, Paul > [ 1010.244334] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:"} > [ 1010.250538] rcu: \t2-...!: (42 GPs behind) idle=884/0/0x0 softirq=1646/1647 fqs=0 (false positive?)"} > [ 1010.259746] rcu: \t3-...!: (1 ticks this GP) idle=134/0/0x0 softirq=3205/3205 fqs=0 (false positive?)"} > [ 1010.269013] \t(detected by 4, t=6502 jiffies, g=9121, q=110)"} > [ 1010.274621] "} > [ 1010.276115] ============================================"} > [ 1010.281438] WARNING: possible recursive locking detected"} > [ 1010.286763] 5.10.43-g92fdbb553f50-ab979 #1 Not tainted"} > [ 1010.291912] --------------------------------------------"} > [ 1010.297235] swapper/4/0 is trying to acquire lock:"} > [ 1010.302037] ffff8000121fe618 (rcu_node_0){-.-.}-{2:2}, at: rcu_dump_cpu_stacks+0x60/0xf8"} > [ 1010.310183] "} > [ 1010.310183] but task is already holding lock:"} > [ 1010.316028] ffff8000121fe618 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0x658/0xca0"} > [ 1010.324341] "} > [ 1010.324341] other info that might help us debug this:"} > [ 1010.330882] Possible unsafe locking scenario:"} > [ 1010.330882] "} > [ 1010.336813] CPU0"} > [ 1010.339263] ----"} > [ 1010.341713] lock(rcu_node_0);"} > [ 1010.344872] lock(rcu_node_0);"} > [ 1010.348029] "} > [ 1010.348029] *** DEADLOCK ***"} > [ 1010.348029] "} > [ 1010.353961] May be due to missing lock nesting notation"} > [ 1010.353961] "} > [ 1010.360764] 1 lock held by swapper/4/0:"} > [ 1010.364607] #0: ffff8000121fe618 (rcu_node_0){-.-.}-{2:2}, at: rcu_sched_clock_irq+0x658/0xca0"} > [ 1010.373359] "} > [ 1010.373359] stack backtrace:"} > [ 1010.377729] CPU: 4 PID: 0 Comm: swapper/4 Not tainted 5.10.43-g92fdbb553f50-ab979 #1"} > [ 1010.385489] Hardware name: ARM Juno development board (r0) (DT)"} > [ 1010.391421] Call trace:"} > [ 1010.393877] dump_backtrace+0x0/0x1c0"} > [ 1010.397551] show_stack+0x24/0x30"} > [ 1010.400877] dump_stack_lvl+0xf4/0x130"} > [ 1010.404636] dump_stack+0x18/0x58"} > [ 1010.407962] __lock_acquire+0xa18/0x1ffc"} > [ 1010.411895] lock_acquire.part.0+0xc8/0x30c"} > [ 1010.416089] lock_acquire+0x68/0x84"} > [ 1010.419589] _raw_spin_lock_irqsave+0x84/0x158"} > [ 1010.424045] rcu_dump_cpu_stacks+0x60/0xf8"} > [ 1010.428154] rcu_sched_clock_irq+0x8d8/0xca0"} > [ 1010.432435] update_process_times+0x6c/0xb0"} > [ 1010.436632] tick_sched_handle+0x3c/0x60"} > [ 1010.440566] tick_sched_timer+0x58/0xb0"} > [ 1010.444412] __hrtimer_run_queues+0x1a4/0x5b0"} > [ 1010.448781] hrtimer_interrupt+0xf4/0x2cc"} > [ 1010.452803] arch_timer_handler_phys+0x40/0x50"} > [ 1010.457260] handle_percpu_devid_irq+0x98/0x180"} > [ 1010.461803] __handle_domain_irq+0x80/0xec"} > [ 1010.465911] gic_handle_irq+0x5c/0xf0"} > [ 1010.469583] el1_irq+0xcc/0x180"} > [ 1010.472735] cpuidle_enter_state+0xe8/0x350"} > [ 1010.476929] cpuidle_enter+0x44/0x60"} > [ 1010.480515] do_idle+0x25c/0x2f0"} > [ 1010.483751] cpu_startup_entry+0x34/0x8c"} > [ 1010.487687] secondary_start_kernel+0x154/0x190"} > > > Thanks > > -- > Qais Yousef