From patchwork Wed Nov 9 09:37:36 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 13037291 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 0452DC4332F for ; Wed, 9 Nov 2022 09:38:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230003AbiKIJi3 (ORCPT ); Wed, 9 Nov 2022 04:38:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229591AbiKIJi1 (ORCPT ); Wed, 9 Nov 2022 04:38:27 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D4EB26DD; Wed, 9 Nov 2022 01:38:26 -0800 (PST) Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4N6fyw1FCFzHvkk; Wed, 9 Nov 2022 17:38:00 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 9 Nov 2022 17:38:24 +0800 Received: from thunder-town.china.huawei.com (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 9 Nov 2022 17:38:24 +0800 From: Zhen Lei To: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , "Josh Triplett" , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , , CC: Zhen Lei , Robert Elliott Subject: [PATCH v6 0/2] rcu: Add RCU stall diagnosis information Date: Wed, 9 Nov 2022 17:37:36 +0800 Message-ID: <20221109093739.187-1-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.37.3.windows.1 MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org 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 (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(+)