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 C0548C433EF for ; Thu, 13 Jan 2022 02:15:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231623AbiAMCPw (ORCPT ); Wed, 12 Jan 2022 21:15:52 -0500 Received: from ec2-13-52-33-57.us-west-1.compute.amazonaws.com ([13.52.33.57]:15055 "EHLO aurora.tech" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S231594AbiAMCPm (ORCPT ); Wed, 12 Jan 2022 21:15:42 -0500 Received: by aurora.tech (Postfix, from userid 1001) id E6C3E16402F3; Tue, 11 Jan 2022 15:33:15 -0800 (PST) From: Alison Chaiken To: tglx@linutronix.de Cc: peterz@infradead.org, paulmck@kernel.org, valentin.schneider@arm.com, frederic@kernel.org, linux-kernel@vger.kernel.org, glenn@aurora.tech, alison@she-devel.com, Alison Chaiken Subject: [PATCH 0/5] handle kthread_prio kernel cmdline parameter consistently Date: Tue, 11 Jan 2022 15:32:49 -0800 Message-Id: <20220111233253.21692-1-achaiken@aurora.tech> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When CONFIG_PREEMPT_RT=y, RCU_SOFTIRQ work is moved to dedicated rcuc per-core threads. The rcutree.kthread_prio kernel cmdline parameter controls the priority of those threads. A provided kthread_prio kernel cmdline parameter also elevates the priority of rcuog threads, but only if they are launched from rcu_spawn_gp_kthread(), not if they are launched from rcu_spawn_one_nocb_kthread(). Fix this inconsistency. When CONFIG_RCU_NOCB_CPU=y, an rcu_nocbs command-line parameter offloads the work of rcuc on designated cores to new rcuop threads that are not pinned to the cores whose expired grace-period timer callbacks they run. While rcuop threads have the same function as rcuc threads, their priority is not controlled by the kthread_prio parameter. Add this feature and update the documentation accordingly. Alison Chaiken (4): RCU: move kthread_prio bounds-check to a separate function RCU: make priority of grace-period thread consistent RCU: elevate priority of offloaded callback threads RCU: update documentation regarding kthread_prio cmdline parameter .../admin-guide/kernel-parameters.txt | 2 + kernel/rcu/tree.c | 42 +++++++++++-------- kernel/rcu/tree_nocb.h | 7 ++++ 3 files changed, 34 insertions(+), 17 deletions(-) -- 2.32.0