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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F3EC6C4332F for ; Wed, 9 Nov 2022 15:26:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232072AbiKIP02 (ORCPT ); Wed, 9 Nov 2022 10:26:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232084AbiKIP0Z (ORCPT ); Wed, 9 Nov 2022 10:26:25 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC463BE05; Wed, 9 Nov 2022 07:26:24 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8774361B91; Wed, 9 Nov 2022 15:26:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60098C433D7; Wed, 9 Nov 2022 15:26:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668007583; bh=Pymxl7n2ZYnyw0RfNbgM6GPwZJA+tDvhsLK+AEj1BeY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TB7ExP5ufy4aISASgWuc05goswVICGpEEyRnvHQ4or/hixANtp2I5+tbwEr5fjdnQ olZKSDmVszAsEw7exmnEZuMP6qBhD33QC+nsmUDlrZdhA2JmZPbbD/KbcLEpmlf3y5 L6FrDmNfgYg7ekPK5yaUYOyWkiuKAoqrYfuN6fjYXg3R4DyHsz80rdTqb/5oKnj6ZT kMN1XKW/xATlZokeu6gzkLmxW1rIukitaluvjHlovSbShoG1j0JW6XErOPfZ2qKhQz HAh3o+2+J1RLx2/tIWKVxjeiFjdoUL2JARn+FTF2Bzg4z8Z8Ic0e4bNvLhsVll33Cs xIjccerdW8vPw== Date: Wed, 9 Nov 2022 16:26:21 +0100 From: Frederic Weisbecker To: Zhen Lei Cc: "Paul E . McKenney" , Neeraj Upadhyay , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Robert Elliott Subject: Re: [PATCH v6 0/2] rcu: Add RCU stall diagnosis information Message-ID: <20221109152621.GB298683@lothringen> References: <20221109093739.187-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221109093739.187-1-thunder.leizhen@huawei.com> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Hi Zhen Lei, On Wed, Nov 09, 2022 at 05:37:36PM +0800, Zhen Lei wrote: > v5 --> v6: > 1. When there are more than two continuous RCU stallings, correctly handle the > value of the second and subsequent sampling periods. Update comments and > document. > Thanks to Elliott, Robert for the test. > 2. Change "rcu stall" to "RCU stall". > > v4 --> v5: > 1. Resolve a git am conflict. No code change. > > v3 --> v4: > 1. Rename rcu_cpu_stall_deep_debug to rcu_cpu_stall_cputime. > > v2 --> v3: > 1. Fix the return type of kstat_cpu_irqs_sum() > 2. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter > rcupdate.rcu_cpu_stall_deep_debug. > 3. Add comments and normalize local variable name > > > v1 --> v2: > 1. Fixed a bug in the code. If the rcu stall is detected by another CPU, > kcpustat_this_cpu cannot be used. > @@ -451,7 +451,7 @@ static void print_cpu_stat_info(int cpu) > if (r->gp_seq != rdp->gp_seq) > return; > > - cpustat = kcpustat_this_cpu->cpustat; > + cpustat = kcpustat_cpu(cpu).cpustat; > 2. Move the start point of statistics from rcu_stall_kick_kthreads() to > rcu_implicit_dynticks_qs(), removing the dependency on irq_work. > > v1: > In some extreme cases, such as the I/O pressure test, the CPU usage may > be 100%, causing RCU stall. In this case, the printed information about > current is not useful. Displays the number and usage of hard interrupts, > soft interrupts, and context switches that are generated within half of > the CPU stall timeout, can help us make a general judgment. In other > cases, we can preliminarily determine whether an infinite loop occurs > when local_irq, local_bh or preempt is disabled. That looks useful but I have to ask: what does it bring that the softlockup and hardlockup watchdog can not already solve? Thanks. > > Zhen Lei (2): > rcu: Add RCU stall diagnosis information > doc: Document CONFIG_RCU_CPU_STALL_CPUTIME=y stall information > > Documentation/RCU/stallwarn.rst | 88 +++++++++++++++++++ > .../admin-guide/kernel-parameters.txt | 6 ++ > kernel/rcu/Kconfig.debug | 11 +++ > kernel/rcu/rcu.h | 1 + > kernel/rcu/tree.c | 17 ++++ > kernel/rcu/tree.h | 19 ++++ > kernel/rcu/tree_stall.h | 29 ++++++ > kernel/rcu/update.c | 2 + > 8 files changed, 173 insertions(+) > > -- > 2.25.1 >