From: Liu Song Date: Thu, 21 Feb 2019 14:13:27 +0000 (+0800) Subject: rcu: Set rcutree.kthread_prio sysfs access to read-only X-Git-Tag: v5.2-rc1~212^2^2^2^3~13 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3ffe3d1adc0b6cfb9b24db9995a537bb0aa30a8b;p=users%2Fjedix%2Flinux-maple.git rcu: Set rcutree.kthread_prio sysfs access to read-only The rcutree.kthread_prio kernel-boot parameter is used to set the priority for boost (rcub), per-CPU (rcuc), and grace-period (rcu_preempt or rcu_sched) kthreads. It is also used by rcutorture to check whether it is possible to meaningfully test RCU priority boosting. However, all of these cases will either ignore or be confused by any post-boot changes to rcutree.kthread_prio. Note that the user really can change the priorities of all of these kthreads using chrt, given sufficient privileges. Therefore, the read-write nature of sysfs access to rcutree.kthread_prio is thus at best an attractive nuisance. This commit therefore changes sysfs access to rcutree.kthread_prio to be read-only. Signed-off-by: Liu Song Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2f78a115d34cd..296131450414e 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -149,7 +149,7 @@ static void sync_sched_exp_online_cleanup(int cpu); /* rcuc/rcub kthread realtime priority */ static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; -module_param(kthread_prio, int, 0644); +module_param(kthread_prio, int, 0444); /* Delay in jiffies for grace-period initialization delays, debug only. */