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>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index c95fa89ffef9d4bce14b3dc272e55aba5c8055ef..8455043c9250200d96e68ace1115c5b55aed6bc4 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -131,8 +131,6 @@ static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
 static void invoke_rcu_core(void);
 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
 
-#define RCU_KTHREAD_PRIO 1     /* RT priority for per-CPU kthreads. */
-
 /*
  * Track the rcutorture test sequence number and the update version
  * number within a given test.  The rcutorture_testseq is incremented

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f6c63eac72d4937969bc24615f4590ccaed39105..509d5a31c8ac100e520b6e572588ed825d02d840 100644 (file)
--- 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
@@ -1365,13 +1373,13 @@ 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;
@@ -1466,6 +1474,7 @@ 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);
@@ -1473,7 +1482,8 @@ 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);
 }
@@ -1592,7 +1602,7 @@ 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))
@@ -1701,7 +1711,7 @@ 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);