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Subject[PATCH tip/core/rcu 44/55] rcu: wire up RCU_BOOST_PRIO for rcutree
Date
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>
---
kernel/rcutree.c | 2 --
kernel/rcutree_plugin.h | 20 +++++++++++++++-----
2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index c95fa89..8455043 100644
--- 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 f6c63ea..f751a2d 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
@@ -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->normal_prio;

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);
--
1.7.3.2


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