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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D65ECC433F5 for ; Wed, 17 Nov 2021 15:57:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B954461B1B for ; Wed, 17 Nov 2021 15:57:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238886AbhKQP75 (ORCPT ); Wed, 17 Nov 2021 10:59:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:48342 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238836AbhKQP7w (ORCPT ); Wed, 17 Nov 2021 10:59:52 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id C72A360EE4; Wed, 17 Nov 2021 15:56:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637164613; bh=7ewpNnh/3IQEiTEnxe1PLjl/G76/xv32y7m+ACP7XLI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NX0kTcrpWzTlLAax3dLBHcRxF2zximqx8s6l00ez7i6Tye2GyhCO8axdnOqqzQRSl 1X54YzipMUkkQ5+kEfMtMGp6LoIEwgwBvQ5TGxwTt5ppSLrUKbjhFOuZTAJo1o4RXZ KhD7rKSTKRuH+xPJRlthcJYW6lf8uSgaWwPCYYgIJMeoMgaONvFO1eDD3/JOHutrCU rYDTdW/O7V0ZnuF3ARhQccwxcpGGvdC59eHCKpwfhjLGn1M9O0gZ4gJFm2AKZfV7y6 2vIiLb//3qqR6ZBHIJDn0d70pFTY4C3kHJ/otMgdY3SlbCCpouz3EaQCZTUTU52sC2 CkYRFL5JQzepw== From: Frederic Weisbecker To: "Paul E . McKenney" Cc: LKML , Frederic Weisbecker , Uladzislau Rezki , Neeraj Upadhyay , Boqun Feng , Josh Triplett , Joel Fernandes , rcu@vger.kernel.org Subject: [PATCH 4/6] rcu/nocb: Create nocb kthreads on all CPUs as long as the "rcu_nocb=" is passed Date: Wed, 17 Nov 2021 16:56:35 +0100 Message-Id: <20211117155637.363706-5-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211117155637.363706-1-frederic@kernel.org> References: <20211117155637.363706-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In order to be able to (de-)offload any CPU using cpuset in the future, create a NOCB kthread for all possible CPUs. For now this is done only as long as the "rcu_nocb=" kernel parameter is passed to avoid the unnecessary overhead for most users. Signed-off-by: Frederic Weisbecker Cc: Neeraj Upadhyay Cc: Boqun Feng Cc: Uladzislau Rezki Cc: Josh Triplett Cc: Joel Fernandes --- kernel/rcu/tree_nocb.h | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 9fe4be10fde7..1871f15b8472 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1221,11 +1221,8 @@ static void rcu_spawn_one_nocb_kthread(int cpu) struct rcu_data *rdp_gp; struct task_struct *t; - /* - * If this isn't a no-CBs CPU or if it already has an rcuo kthread, - * then nothing to do. - */ - if (!rcu_is_nocb_cpu(cpu) || rdp->nocb_cb_kthread) + /* If it already has an rcuo kthread, then nothing to do. */ + if (rdp->nocb_cb_kthread) return; /* If we didn't spawn the GP kthread first, reorganize! */ @@ -1253,7 +1250,7 @@ static void rcu_spawn_one_nocb_kthread(int cpu) */ static void rcu_spawn_cpu_nocb_kthread(int cpu) { - if (rcu_scheduler_fully_active) + if (rcu_scheduler_fully_active && rcu_nocb_is_setup) rcu_spawn_one_nocb_kthread(cpu); } @@ -1268,7 +1265,7 @@ static void __init rcu_spawn_nocb_kthreads(void) int cpu; if (rcu_nocb_is_setup) { - for_each_online_cpu(cpu) + for_each_possible_cpu(cpu) rcu_spawn_cpu_nocb_kthread(cpu); } } @@ -1303,7 +1300,7 @@ static void __init rcu_organize_nocb_kthreads(void) * Should the corresponding CPU come online in the future, then * we will spawn the needed set of rcu_nocb_kthread() kthreads. */ - for_each_cpu(cpu, rcu_nocb_mask) { + for_each_possible_cpu(cpu) { rdp = per_cpu_ptr(&rcu_data, cpu); if (rdp->cpu >= nl) { /* New GP kthread, set up for CBs & next GP. */ @@ -1327,7 +1324,8 @@ static void __init rcu_organize_nocb_kthreads(void) pr_cont(" %d", cpu); } rdp->nocb_gp_rdp = rdp_gp; - list_add_tail(&rdp->nocb_entry_rdp, &rdp_gp->nocb_head_rdp); + if (cpumask_test_cpu(cpu, rcu_nocb_mask)) + list_add_tail(&rdp->nocb_entry_rdp, &rdp_gp->nocb_head_rdp); } if (gotnocbs && dump_tree) pr_cont("%s\n", gotnocbscbs ? "" : " (self only)"); -- 2.25.1