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Date: Tue, 28 Jul 2015 16:39:31 +0200
From: Petr Mladek <pmladek@...e.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Josh Triplett <josh@...htriplett.org>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
Vlastimil Babka <vbabka@...e.cz>,
live-patching@...r.kernel.org, linux-api@...r.kernel.org,
linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>
Subject: [RFC PATCH 14/14] kthread_worker: Add set_kthread_worker_scheduler*()
The kthread worker API will be used for kthreads that need to modify
the scheduling policy.
This patch adds a function that allows to make it easily, safe way,
and hides implementation details. It might even help to get rid
of an init work.
It uses @sched_priority as a parameter instead of struct sched_param.
The structure has been there already in the initial kernel git commit
(April 2005) and always included only one member: sched_priority.
So, it rather looks like an overkill that is better to hide.
Signed-off-by: Petr Mladek <pmladek@...e.com>
---
include/linux/kthread.h | 5 +++
kernel/kthread.c | 59 ++++++++++++++++++++++++++++++++++++
kernel/rcu/tree.c | 10 +++---
kernel/trace/ring_buffer_benchmark.c | 11 +++----
4 files changed, 72 insertions(+), 13 deletions(-)
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index b75847e1a4c9..d503dc16613c 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -144,6 +144,11 @@ int create_kthread_worker_on_node(struct kthread_worker *worker,
void set_kthread_worker_user_nice(struct kthread_worker *worker, long nice);
+int set_kthread_worker_scheduler(struct kthread_worker *worker,
+ int policy, int sched_priority);
+int set_kthread_worker_scheduler_nocheck(struct kthread_worker *worker,
+ int policy, int sched_priority);
+
bool queue_kthread_work(struct kthread_worker *worker,
struct kthread_work *work);
void flush_kthread_work(struct kthread_work *work);
diff --git a/kernel/kthread.c b/kernel/kthread.c
index ab2e235b6144..4ab31b914676 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -662,6 +662,65 @@ void set_kthread_worker_user_nice(struct kthread_worker *worker, long nice)
}
EXPORT_SYMBOL(set_kthread_worker_user_nice);
+static int
+__set_kthread_worker_scheduler(struct kthread_worker *worker,
+ int policy, int sched_priority, bool check)
+{
+ struct task_struct *task = worker->task;
+ const struct sched_param sp = {
+ .sched_priority = sched_priority
+ };
+ int ret;
+
+ WARN_ON(!task);
+
+ if (check)
+ ret = sched_setscheduler(task, policy, &sp);
+ else
+ ret = sched_setscheduler_nocheck(task, policy, &sp);
+
+ return ret;
+}
+
+/**
+ * set_kthread_worker_scheduler - change the scheduling policy and/or RT
+ * priority of a kthread worker.
+ * @worker: target kthread_worker
+ * @policy: new policy
+ * @sched_priority: new RT priority
+ *
+ * Return: 0 on success. An error code otherwise.
+ */
+int set_kthread_worker_scheduler(struct kthread_worker *worker,
+ int policy, int sched_priority)
+{
+ return __set_kthread_worker_scheduler(worker, policy, sched_priority,
+ true);
+}
+EXPORT_SYMBOL(set_kthread_worker_scheduler);
+
+/**
+ * set_kthread_worker_scheduler_nocheck - change the scheduling policy and/or RT
+ * priority of a kthread worker.
+ * @worker: target kthread_worker
+ * @policy: new policy
+ * @sched_priority: new RT priority
+ *
+ * Just like set_kthread_worker_sheduler(), only don't bother checking
+ * if the current context has permission. For example, this is needed
+ * in stop_machine(): we create temporary high priority worker threads,
+ * but our caller might not have that capability.
+ *
+ * Return: 0 on success. An error code otherwise.
+ */
+int set_kthread_worker_scheduler_nocheck(struct kthread_worker *worker,
+ int policy, int sched_priority)
+{
+ return __set_kthread_worker_scheduler(worker, policy, sched_priority,
+ false);
+}
+EXPORT_SYMBOL(set_kthread_worker_scheduler_nocheck);
+
/* insert @work before @pos in @worker */
static void insert_kthread_work(struct kthread_worker *worker,
struct kthread_work *work,
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 3a286f3b8b3c..d882464c71d7 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3916,7 +3916,6 @@ static int __init rcu_spawn_gp_kthread(void)
int kthread_prio_in = kthread_prio;
struct rcu_node *rnp;
struct rcu_state *rsp;
- struct sched_param sp;
int ret;
/* Force priority into range. */
@@ -3940,11 +3939,10 @@ static int __init rcu_spawn_gp_kthread(void)
BUG_ON(ret);
rnp = rcu_get_root(rsp);
raw_spin_lock_irqsave(&rnp->lock, flags);
- if (kthread_prio) {
- sp.sched_priority = kthread_prio;
- sched_setscheduler_nocheck(rsp->gp_worker.task,
- SCHED_FIFO, &sp);
- }
+ if (kthread_prio)
+ set_kthread_worker_scheduler_nocheck(&rsp->gp_worker,
+ SCHED_FIFO,
+ kthread_prio);
queue_kthread_work(&rsp->gp_worker, &rsp->gp_init_work);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c
index 73e4c7f11a2c..89028165bb22 100644
--- a/kernel/trace/ring_buffer_benchmark.c
+++ b/kernel/trace/ring_buffer_benchmark.c
@@ -469,13 +469,10 @@ static int __init ring_buffer_benchmark_init(void)
set_user_nice(consumer, consumer_nice);
}
- if (producer_fifo >= 0) {
- struct sched_param param = {
- .sched_priority = producer_fifo
- };
- sched_setscheduler(rb_producer_worker.task,
- SCHED_FIFO, ¶m);
- } else
+ if (producer_fifo >= 0)
+ set_kthread_worker_scheduler(&rb_producer_worker,
+ SCHED_FIFO, producer_fifo);
+ else
set_kthread_worker_user_nice(&rb_producer_worker,
producer_nice);
--
1.8.5.6
--
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