rcu: Start RCU kthreads in TASK_INTERRUPTIBLE state

Upon creation, kthreads are in TASK_UNINTERRUPTIBLE state, which can
result in softlockup warnings.  Because some of RCU's kthreads can
legitimately be idle indefinitely, start them in TASK_INTERRUPTIBLE
state in order to avoid those warnings.

Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 05e254e..77a7671 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1648,6 +1648,7 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
        if (IS_ERR(t))
                return PTR_ERR(t);
        kthread_bind(t, cpu);
+       set_task_state(t, TASK_INTERRUPTIBLE);
        per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
        WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
        per_cpu(rcu_cpu_kthread_task, cpu) = t;
@@ -1755,6 +1756,7 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
                if (IS_ERR(t))
                        return PTR_ERR(t);
                raw_spin_lock_irqsave(&rnp->lock, flags);
+               set_task_state(t, TASK_INTERRUPTIBLE);
                rnp->node_kthread_task = t;
                raw_spin_unlock_irqrestore(&rnp->lock, flags);
                sp.sched_priority = 99;

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 049f278..a767b7d 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1295,6 +1295,7 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
        if (IS_ERR(t))
                return PTR_ERR(t);
        raw_spin_lock_irqsave(&rnp->lock, flags);
+       set_task_state(t, TASK_INTERRUPTIBLE);
        rnp->boost_kthread_task = t;
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
        sp.sched_priority = RCU_KTHREAD_PRIO;