linux-kernel - [PATCH 0/5] handle kthread_prio kernel cmdline parameter consistently

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Date:   Tue, 11 Jan 2022 15:32:49 -0800
From:   Alison Chaiken <achaiken@...ora.tech>
To:     tglx@...utronix.de
Cc:     peterz@...radead.org, paulmck@...nel.org,
        valentin.schneider@....com, frederic@...nel.org,
        linux-kernel@...r.kernel.org, glenn@...ora.tech,
        alison@...-devel.com, Alison Chaiken <achaiken@...ora.tech>
Subject: [PATCH 0/5] handle kthread_prio kernel cmdline parameter consistently

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