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>
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						Ingo Molnar
					
				
			
			
				
	
			
			
			
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			@@ -1648,6 +1648,7 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
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	if (IS_ERR(t))
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		return PTR_ERR(t);
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	kthread_bind(t, cpu);
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	set_task_state(t, TASK_INTERRUPTIBLE);
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	per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
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	WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
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	per_cpu(rcu_cpu_kthread_task, cpu) = t;
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@@ -1755,6 +1756,7 @@ static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
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		if (IS_ERR(t))
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			return PTR_ERR(t);
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		raw_spin_lock_irqsave(&rnp->lock, flags);
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		set_task_state(t, TASK_INTERRUPTIBLE);
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		rnp->node_kthread_task = t;
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		raw_spin_unlock_irqrestore(&rnp->lock, flags);
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		sp.sched_priority = 99;
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@@ -1295,6 +1295,7 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
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	if (IS_ERR(t))
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		return PTR_ERR(t);
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	raw_spin_lock_irqsave(&rnp->lock, flags);
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	set_task_state(t, TASK_INTERRUPTIBLE);
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	rnp->boost_kthread_task = t;
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	raw_spin_unlock_irqrestore(&rnp->lock, flags);
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	sp.sched_priority = RCU_KTHREAD_PRIO;
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