From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
Liu Song <fishland@aliyun.com>, Liu Song <liu.song11@zte.com.cn>,
"Paul E . McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH tip/core/rcu 05/18] rcu: Set rcutree.kthread_prio sysfs access to read-only
Date: Tue, 26 Mar 2019 16:13:01 -0700 [thread overview]
Message-ID: <20190326231314.19518-5-paulmck@linux.ibm.com> (raw)
In-Reply-To: <20190326231253.GA18343@linux.ibm.com>
From: Liu Song <fishland@aliyun.com>
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 <liu.song11@zte.com.cn>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
---
kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2f78a115d34c..296131450414 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. */
--
2.17.1
next prev parent reply other threads:[~2019-03-26 23:13 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 23:12 [PATCH tip/core/rcu 0/18] Miscellaneous fixes for v5.2 Paul E. McKenney
2019-03-26 23:12 ` [PATCH tip/core/rcu 01/18] rcu: Unconditionally expedite during suspend/hibernate Paul E. McKenney
2019-03-26 23:12 ` [PATCH tip/core/rcu 02/18] rcu: Avoid unnecessary softirq when system is idle Paul E. McKenney
2019-03-26 23:12 ` [PATCH tip/core/rcu 03/18] rcu: rcu_qs -- Use raise_softirq_irqoff to not save irqs twice Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 04/18] rcu: Make exit_rcu() handle non-preempted RCU readers Paul E. McKenney
2019-03-26 23:13 ` Paul E. McKenney [this message]
2019-03-26 23:13 ` [PATCH tip/core/rcu 06/18] MAINTAINERS: RCU now has its own email list Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 07/18] MAINTAINERS: Add -rcu branch name ("dev") Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 08/18] rcu: Move common code out of if-else block Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 09/18] rcu: Allow rcu_nocbs= to specify all CPUs Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 10/18] rcu: Report error for bad rcu_nocbs= parameter values Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 11/18] rcu: Fix self-wakeups for grace-period kthread Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 12/18] rcu: Default jiffies_to_sched_qs to jiffies_till_sched_qs Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 13/18] rcu: Do a single rhp->func read in rcu_head_after_call_rcu() Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 14/18] rcu: Update jiffies_to_sched_qs and adjust_jiffies_till_sched_qs() comments Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 15/18] rcu: Fix force_qs_rnp() header comment Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 16/18] rcu: Eliminate redundant NULL-pointer check Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 17/18] rcu: Fix typo in tree_exp.h comment Paul E. McKenney
2019-03-26 23:13 ` [PATCH tip/core/rcu 18/18] rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_special Paul E. McKenney
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