rcu: Wire up RCU_BOOST_PRIO for rcutree

RCU boost threads start life at RCU_BOOST_PRIO, while others remain
at RCU_KTHREAD_PRIO.  While here, change thread names to match other
kthreads, and adjust rcu_yield() to not override the priority set by
the user.  This last change sets the stage for runtime changes to
priority in the -rt tree.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 15 insertions, 5 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 28422767d854..b4cbe5bf2326 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -27,6 +27,14 @@
 #include <linux/delay.h>
 #include <linux/stop_machine.h>
 
+#define RCU_KTHREAD_PRIO 1
+
+#ifdef CONFIG_RCU_BOOST
+#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
+#else
+#define RCU_BOOST_PRIO RCU_KTHREAD_PRIO
+#endif
+
 /*
  * Check the RCU kernel configuration parameters and print informative
  * messages about anything out of the ordinary.  If you like #ifdef, you
@@ -1364,13 +1372,13 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
         if (rnp->boost_kthread_task != NULL)
                 return 0;
         t = kthread_create(rcu_boost_kthread, (void *)rnp,
-                           "rcub%d", rnp_index);
+                           "rcub/%d", rnp_index);
         if (IS_ERR(t))
                 return PTR_ERR(t);
         raw_spin_lock_irqsave(&rnp->lock, flags);
         rnp->boost_kthread_task = t;
         raw_spin_unlock_irqrestore(&rnp->lock, flags);
-        sp.sched_priority = RCU_KTHREAD_PRIO;
+        sp.sched_priority = RCU_BOOST_PRIO;
         sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
         wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
         return 0;
@@ -1465,6 +1473,7 @@ static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
 {
         struct sched_param sp;
         struct timer_list yield_timer;
+        int prio = current->rt_priority;
 
         setup_timer_on_stack(&yield_timer, f, arg);
         mod_timer(&yield_timer, jiffies + 2);
@@ -1472,7 +1481,8 @@ static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
         sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
         set_user_nice(current, 19);
         schedule();
-        sp.sched_priority = RCU_KTHREAD_PRIO;
+        set_user_nice(current, 0);
+        sp.sched_priority = prio;
         sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
         del_timer(&yield_timer);
 }
@@ -1591,7 +1601,7 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
         t = kthread_create_on_node(rcu_cpu_kthread,
                                    (void *)(long)cpu,
                                    cpu_to_node(cpu),
-                                   "rcuc%d", cpu);
+                                   "rcuc/%d", cpu);
         if (IS_ERR(t))
                 return PTR_ERR(t);
         if (cpu_online(cpu))
@@ -1700,7 +1710,7 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
                 return 0;
         if (rnp->node_kthread_task == NULL) {
                 t = kthread_create(rcu_node_kthread, (void *)rnp,
-                                   "rcun%d", rnp_index);
+                                   "rcun/%d", rnp_index);
                 if (IS_ERR(t))
                         return PTR_ERR(t);
                 raw_spin_lock_irqsave(&rnp->lock, flags);