From patchwork Wed Aug 17 01:42:53 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 12945409 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 57C85C32771 for ; Wed, 17 Aug 2022 01:43:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238085AbiHQBnf (ORCPT ); Tue, 16 Aug 2022 21:43:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238282AbiHQBne (ORCPT ); Tue, 16 Aug 2022 21:43:34 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 80AE8422F4; Tue, 16 Aug 2022 18:43:32 -0700 (PDT) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4M6rLL0V4NzkWRt; Wed, 17 Aug 2022 09:40:10 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Wed, 17 Aug 2022 09:43:30 +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 15.1.2375.24; Wed, 17 Aug 2022 09:43:30 +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 Subject: [PATCH v4 2/2] rcu: Simplify the code logic of rcu_init_nohz() Date: Wed, 17 Aug 2022 09:42:53 +0800 Message-ID: <20220817014253.1982-3-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.26.0.windows.1 In-Reply-To: <20220817014253.1982-1-thunder.leizhen@huawei.com> References: <20220817014253.1982-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org When CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional CPUs need to be added to 'rcu_nocb_mask'. But 'rcu_nocb_mask' may be not available now, due to 'rcu_nocbs' is not specified. Check and initialize 'rcu_nocb_mask' before using it. This code simplification strictly follows this logic, compared with old implementations, unnecessary crossovers are avoided and easy to understand. Signed-off-by: Zhen Lei --- kernel/rcu/tree_nocb.h | 32 +++++++++----------------------- 1 file changed, 9 insertions(+), 23 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index ff763e7dc53551f..3c59b12f4465af1 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1209,44 +1209,30 @@ EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload); void __init rcu_init_nohz(void) { int cpu; - bool need_rcu_nocb_mask = false; - bool offload_all = false; struct rcu_data *rdp; + const struct cpumask *cpumask = NULL; #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) - if (!cpumask_available(rcu_nocb_mask)) { - need_rcu_nocb_mask = true; - offload_all = true; - } -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ - -#if defined(CONFIG_NO_HZ_FULL) - if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) { - need_rcu_nocb_mask = true; - offload_all = false; /* NO_HZ_FULL has its own mask. */ - } -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ + cpumask = cpu_possible_mask; +#elif defined(CONFIG_NO_HZ_FULL) + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) + cpumask = tick_nohz_full_mask; +#endif - if (need_rcu_nocb_mask) { + if (cpumask) { if (!cpumask_available(rcu_nocb_mask)) { if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) { pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n"); return; } } + + cpumask_or(rcu_nocb_mask, rcu_nocb_mask, cpumask); } if (!cpumask_available(rcu_nocb_mask)) return; -#if defined(CONFIG_NO_HZ_FULL) - if (tick_nohz_full_running) - cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); -#endif /* #if defined(CONFIG_NO_HZ_FULL) */ - - if (offload_all) - cpumask_setall(rcu_nocb_mask); - if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) { pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n"); cpumask_and(rcu_nocb_mask, cpu_possible_mask,