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 63A59C4332F for ; Tue, 22 Nov 2022 11:59:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233279AbiKVL7i (ORCPT ); Tue, 22 Nov 2022 06:59:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47674 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231583AbiKVL7f (ORCPT ); Tue, 22 Nov 2022 06:59:35 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4B8D513EB0; Tue, 22 Nov 2022 03:59:34 -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 ams.source.kernel.org (Postfix) with ESMTPS id 13A7BB81A09; Tue, 22 Nov 2022 11:59:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D863C433D6; Tue, 22 Nov 2022 11:59:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669118371; bh=awIitadsf/uo1C7l6pvVh4QYBC6b2uHMr5qvDAo+Zvs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BZo7+YFb6KE0Xfg4iZY0adz7ph8k7Q2yTgCQ4Ul963JgXTlUMRMPubmkI7sdeReax LXPv/DojlpOddNPYtD3tC2LK5BitNd7sKQC4Ou1/DK3lCtN3SVY4EjAQgPLHpBVbiw VdFFpvzc4qT//7YyxvfpKIG53GdweNBlIwYqL8laUivXCD7etXBqlE84kK0IPNkyMQ 0zmt9RnbhQ63aTIzPOepNaM9o6as3tpIY1ieWgknUqbBxRDl3Pa1eDo0f/aBw44Crg 6fdsV1qErdGzV17ISPIJz0xEXIxzFC2rgQVWo+hoJo91DuzfvwraSZ45IuDkTj5Up7 oTUAPJ5j9+xeg== Date: Tue, 22 Nov 2022 12:59:28 +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 v8 0/6] rcu: Add RCU stall diagnosis information Message-ID: <20221122115928.GA1158713@lothringen> References: <20221119092508.1766-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221119092508.1766-1-thunder.leizhen@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Nov 19, 2022 at 05:25:02PM +0800, Zhen Lei wrote: > v7 --> v8: > 1. Change call jiffies64_to_msecs() to call jiffies_to_msecs(). > 2. Mention that rcupdate.rcu_cpu_stall_cputime overrides > CONFIG_RCU_CPU_STALL_CPUTIME behaviour in the Kconfig help text. > 3. Fix a make htmldocs warning, change "|...|" to ":...:". > > v6 --> v7: > 1. Use kcpustat_field() to obtain the cputime. > 2. Make the output start with "\t" to match other related prints. > 3. Aligns the output of the last line of RCU stall. > > 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. > > Zhen Lei (6): > genirq: Fix the return type of kstat_cpu_irqs_sum() > sched: Add helper kstat_cpu_softirqs_sum() > sched: Add helper nr_context_switches_cpu() > rcu: Add RCU stall diagnosis information > doc: Document CONFIG_RCU_CPU_STALL_CPUTIME=y stall information > rcu: Align the output of RCU stall Reviewed-by: Frederic Weisbecker Thanks! > > Documentation/RCU/stallwarn.rst | 88 +++++++++++++++++++ > .../admin-guide/kernel-parameters.txt | 6 ++ > include/linux/kernel_stat.h | 14 ++- > kernel/rcu/Kconfig.debug | 13 +++ > kernel/rcu/rcu.h | 1 + > kernel/rcu/tree.c | 18 ++++ > kernel/rcu/tree.h | 19 ++++ > kernel/rcu/tree_stall.h | 35 +++++++- > kernel/rcu/update.c | 2 + > kernel/sched/core.c | 5 ++ > 10 files changed, 198 insertions(+), 3 deletions(-) > > -- > 2.25.1 >