From patchwork Wed Nov 30 18:13:10 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13060211 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 C27E6C4321E for ; Wed, 30 Nov 2022 18:13:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230086AbiK3SNu (ORCPT ); Wed, 30 Nov 2022 13:13:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230120AbiK3SNb (ORCPT ); Wed, 30 Nov 2022 13:13:31 -0500 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E66DD862D4; Wed, 30 Nov 2022 10:13:30 -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 sin.source.kernel.org (Postfix) with ESMTPS id 5F407CE1ACC; Wed, 30 Nov 2022 18:13:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BAC0C433D6; Wed, 30 Nov 2022 18:13:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669832007; bh=KTUh/BBOVf/jDi48jtrSyvr3uGxVW8ae61JQrk9NyJc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W8Ib8dqo0tM2ZZX1nN5aPSqBIQqvc+AFNKQ9RXDNJHY7jdtD5p70hLzIGA+ZplQn9 yNjVd3NK9aPO965vSs9Vxf2u7XONZv0fe7n09XoPaKp9RIKv91a7/I0AQ7kSthytkW Tr4sLMqh6hy03j1NuMEVmSvUV4p4Aw6Ers1Xb9d3m4edfqbeNf2K1i1k8peYxz+01m jFywHwADwCLsnoEfQDXsnQSZERbTmMKe26WKNqh7Ivr5ZSmu4LY07LmV0OSh36uYm2 5yRt7Xd0DlSZXIHyPtgMwz20ir1LCys0eIY5urJHAQqB9g80LnsUGhlFagIHmTJKtZ eZ52DRv0AsnUg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 558095C051C; Wed, 30 Nov 2022 10:13:27 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, Zhen Lei , Joel Fernandes , Frederic Weisbecker , "Paul E . McKenney" Subject: [PATCH rcu 01/16] rcu: Simplify rcu_init_nohz() cpumask handling Date: Wed, 30 Nov 2022 10:13:10 -0800 Message-Id: <20221130181325.1012760-1-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20221130181316.GA1012431@paulmck-ThinkPad-P17-Gen-1> References: <20221130181316.GA1012431@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Zhen Lei In kernels built with either CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y or CONFIG_NO_HZ_FULL=y, additional CPUs must be added to rcu_nocb_mask. Except that kernels booted without the rcu_nocbs= will not have allocated rcu_nocb_mask. And the current rcu_init_nohz() function uses its need_rcu_nocb_mask and offload_all local variables to track the rcu_nocb and nohz_full state. But there is a much simpler approach, namely creating a cpumask pointer to track the default and then using cpumask_available() to check the rcu_nocb_mask state. This commit takes this approach, thereby simplifying and shortening the rcu_init_nohz() function. Signed-off-by: Zhen Lei Reviewed-by: Joel Fernandes (Google) Acked-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_nocb.h | 34 +++++++++++----------------------- 1 file changed, 11 insertions(+), 23 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 0a5f0ef414845..ce526cc2791ca 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1210,45 +1210,33 @@ 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; - -#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) - if (!rcu_state.nocb_is_setup) { - need_rcu_nocb_mask = true; - offload_all = true; - } -#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */ + const struct cpumask *cpumask = NULL; #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) */ + if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) + cpumask = tick_nohz_full_mask; +#endif + + if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) && + !rcu_state.nocb_is_setup && !cpumask) + cpumask = cpu_possible_mask; - 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); rcu_state.nocb_is_setup = true; } if (!rcu_state.nocb_is_setup) 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,