From patchwork Wed Aug 31 18:10:44 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: 12961231 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 881D0ECAAD1 for ; Wed, 31 Aug 2022 18:13:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232377AbiHaSN3 (ORCPT ); Wed, 31 Aug 2022 14:13:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43402 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232403AbiHaSM6 (ORCPT ); Wed, 31 Aug 2022 14:12:58 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9242EF001; Wed, 31 Aug 2022 11:11:52 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id E67B661C41; Wed, 31 Aug 2022 18:10:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4CC76C433D7; Wed, 31 Aug 2022 18:10:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1661969446; bh=kCjYd6SW2FfEw+BYAxl3L5fePtwdhSgZpFPL5cC1jvY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RJVo505mOTBXh7FtbY5V/L6k+gz0akbWJR+WLo5kvnsWpliol/BkiYuu4TFtzTkCZ jKX8i6NJ/AgXajtP7xMCkwJ28iT45Iwa+UgRWDvvV6B4Evca7Df99ZO8H6XPqjAefv prqjIoZusDRZfJ+NxYtkuKZg6swrsiCOsgzTgf+PPiwbgUajU7bTZoGcz1XKZPMZbS d8RGxjxmhmPygucTlXxgdfCz8DJUE1Aras5HpXzpVCQQe+Alzr3UrqmlInBLpVs7wx STycCXcJmbtadNbelPj21X9A8eFTwh0Rql76Es8tnKffEZN5x80ZAppdwDQxGX1mn0 HQEX06uVrC8iA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 0C8255C02A9; Wed, 31 Aug 2022 11:10:46 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, Zhen Lei , "Paul E . McKenney" , Joel Fernandes Subject: [PATCH rcu 3/3] rcu: Simplify rcu_init_nohz() cpumask handling Date: Wed, 31 Aug 2022 11:10:44 -0700 Message-Id: <20220831181044.2694488-3-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220831181040.GA2694278@paulmck-ThinkPad-P17-Gen-1> References: <20220831181040.GA2694278@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 Signed-off-by: Paul E. McKenney Reviewed-by: Joel Fernandes (Google) --- 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 0a5f0ef414845..c8167be2288fa 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1210,45 +1210,31 @@ 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 (!rcu_state.nocb_is_setup) { - 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); 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,