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 73211C433FE for ; Fri, 18 Nov 2022 02:04:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232126AbiKRCEF (ORCPT ); Thu, 17 Nov 2022 21:04:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235011AbiKRCEC (ORCPT ); Thu, 17 Nov 2022 21:04:02 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C44D97A35E; Thu, 17 Nov 2022 18:04:00 -0800 (PST) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4ND0SS6sPMzRpK0; Fri, 18 Nov 2022 10:03:36 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Fri, 18 Nov 2022 10:03:59 +0800 Received: from [10.174.178.55] (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; Fri, 18 Nov 2022 10:03:58 +0800 Subject: Re: [PATCH v7 4/6] rcu: Add RCU stall diagnosis information To: Frederic Weisbecker CC: "Paul E . McKenney" , Neeraj Upadhyay , Josh Triplett , "Steven Rostedt" , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , , , Robert Elliott References: <20221111130709.247-1-thunder.leizhen@huawei.com> <20221111130709.247-5-thunder.leizhen@huawei.com> <20221116223942.GA838972@lothringen> <20221117122238.GC839309@lothringen> <54aa07c4-b7e3-1a0e-e6a3-444573caba16@huawei.com> <20221117142648.GF839309@lothringen> From: "Leizhen (ThunderTown)" Message-ID: Date: Fri, 18 Nov 2022 10:03:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20221117142648.GF839309@lothringen> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/11/17 22:26, Frederic Weisbecker wrote: > On Thu, Nov 17, 2022 at 09:25:44PM +0800, Leizhen (ThunderTown) wrote: >> >> >> On 2022/11/17 20:22, Frederic Weisbecker wrote: >>> On Thu, Nov 17, 2022 at 09:57:18AM +0800, Leizhen (ThunderTown) wrote: >>>> >>>> >>>> On 2022/11/17 6:39, Frederic Weisbecker wrote: >>>>> On Fri, Nov 11, 2022 at 09:07:07PM +0800, Zhen Lei wrote: >>>>>> @@ -262,6 +279,8 @@ struct rcu_data { >>>>>> short rcu_onl_gp_flags; /* ->gp_flags at last online. */ >>>>>> unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ >>>>>> unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ >>>>>> + struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */ >>>>>> + /* the first RCU stall timeout */ >>>>> >>>>> This should be under #ifdef CONFIG_RCU_CPU_STALL_CPUTIME >>>> >>>> This will not work for now because we also support boot option >>>> rcupdate.rcu_cpu_stall_cputime. >>> >>> I'm confused. If CONFIG_RCU_CPU_STALL_CPUTIME=n then rcupdate.rcu_cpu_stall_cputime has >>> no effect, right? >> >> No, rcupdate.rcu_cpu_stall_cputime override CONFIG_RCU_CPU_STALL_CPUTIME. Because >> the default value of CONFIG_RCU_CPU_STALL_CPUTIME is n, so in most cases, we need >> rcupdate.rcu_cpu_stall_cputime as the escape route. >> >> If CONFIG_RCU_CPU_STALL_CPUTIME=y is default, your suggestion is more >> appropriate. > > Oh ok I thought it was a support Kconfig switch. > > Then please just mention that rcupdate.rcu_cpu_stall_cputime overrides > CONFIG_RCU_CPU_STALL_CPUTIME behaviour in the Kconfig help text. Okay, I'll add the description. > > Thanks. > . > -- Regards, Zhen Lei