Commit 7def2be1 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: fix hotplug cpus on ia64 



Cliff Wickman wrote:

> I built an ia64 kernel from Andrew's tree (2.6.26-rc2-mm1)
> and get a very predictable hotplug cpu problem.
> billberry1:/tmp/cpw # ./dis
> disabled cpu 17
> enabled cpu 17
> billberry1:/tmp/cpw # ./dis
> disabled cpu 17
> enabled cpu 17
> billberry1:/tmp/cpw # ./dis
>
> The script that disables the cpu always hangs (unkillable)
> on the 3rd attempt.
>
> And a bit further:
> The kstopmachine thread always sits on the run queue (real time) for about
> 30 minutes before running.

this fix solves some (but not all) issues between CPU hotplug and
RT bandwidth throttling.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e958b360

kernel/sched.c

+11 −4
Original line number Diff line number Diff line
@@ -7513,21 +7513,28 @@ int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls) 
static int update_sched_domains(struct notifier_block *nfb,

				unsigned long action, void *hcpu)

{

	int cpu = (int)(long)hcpu;



	switch (action) {

	case CPU_UP_PREPARE:

	case CPU_UP_PREPARE_FROZEN:

	case CPU_DOWN_PREPARE:

	case CPU_DOWN_PREPARE_FROZEN:

		disable_runtime(cpu_rq(cpu));

		/* fall-through */

	case CPU_UP_PREPARE:

	case CPU_UP_PREPARE_FROZEN:

		detach_destroy_domains(&cpu_online_map);

		free_sched_domains();

		return NOTIFY_OK;



	case CPU_UP_CANCELED:

	case CPU_UP_CANCELED_FROZEN:



	case CPU_DOWN_FAILED:

	case CPU_DOWN_FAILED_FROZEN:

	case CPU_ONLINE:

	case CPU_ONLINE_FROZEN:

		enable_runtime(cpu_rq(cpu));

		/* fall-through */

	case CPU_UP_CANCELED:

	case CPU_UP_CANCELED_FROZEN:

	case CPU_DEAD:

	case CPU_DEAD_FROZEN:

		/*

kernel/sched_rt.c

+104 −5
Original line number Diff line number Diff line
@@ -286,6 +286,9 @@ static int balance_runtime(struct rt_rq *rt_rq) 
			continue;



		spin_lock(&iter->rt_runtime_lock);

		if (iter->rt_runtime == RUNTIME_INF)

			goto next;



		diff = iter->rt_runtime - iter->rt_time;

		if (diff > 0) {

			do_div(diff, weight);
@@ -299,12 +302,105 @@ static int balance_runtime(struct rt_rq *rt_rq) 
				break;

			}

		}

next:

		spin_unlock(&iter->rt_runtime_lock);

	}

	spin_unlock(&rt_b->rt_runtime_lock);



	return more;

}



static void __disable_runtime(struct rq *rq)

{

	struct root_domain *rd = rq->rd;

	struct rt_rq *rt_rq;



	if (unlikely(!scheduler_running))

		return;



	for_each_leaf_rt_rq(rt_rq, rq) {

		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);

		s64 want;

		int i;



		spin_lock(&rt_b->rt_runtime_lock);

		spin_lock(&rt_rq->rt_runtime_lock);

		if (rt_rq->rt_runtime == RUNTIME_INF ||

				rt_rq->rt_runtime == rt_b->rt_runtime)

			goto balanced;

		spin_unlock(&rt_rq->rt_runtime_lock);



		want = rt_b->rt_runtime - rt_rq->rt_runtime;



		for_each_cpu_mask(i, rd->span) {

			struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);

			s64 diff;



			if (iter == rt_rq)

				continue;



			spin_lock(&iter->rt_runtime_lock);

			if (want > 0) {

				diff = min_t(s64, iter->rt_runtime, want);

				iter->rt_runtime -= diff;

				want -= diff;

			} else {

				iter->rt_runtime -= want;

				want -= want;

			}

			spin_unlock(&iter->rt_runtime_lock);



			if (!want)

				break;

		}



		spin_lock(&rt_rq->rt_runtime_lock);

		BUG_ON(want);

balanced:

		rt_rq->rt_runtime = RUNTIME_INF;

		spin_unlock(&rt_rq->rt_runtime_lock);

		spin_unlock(&rt_b->rt_runtime_lock);

	}

}



static void disable_runtime(struct rq *rq)

{

	unsigned long flags;



	spin_lock_irqsave(&rq->lock, flags);

	__disable_runtime(rq);

	spin_unlock_irqrestore(&rq->lock, flags);

}



static void __enable_runtime(struct rq *rq)

{

	struct root_domain *rd = rq->rd;

	struct rt_rq *rt_rq;



	if (unlikely(!scheduler_running))

		return;



	for_each_leaf_rt_rq(rt_rq, rq) {

		struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);



		spin_lock(&rt_b->rt_runtime_lock);

		spin_lock(&rt_rq->rt_runtime_lock);

		rt_rq->rt_runtime = rt_b->rt_runtime;

		rt_rq->rt_time = 0;

		spin_unlock(&rt_rq->rt_runtime_lock);

		spin_unlock(&rt_b->rt_runtime_lock);

	}

}



static void enable_runtime(struct rq *rq)

{

	unsigned long flags;



	spin_lock_irqsave(&rq->lock, flags);

	__enable_runtime(rq);

	spin_unlock_irqrestore(&rq->lock, flags);

}



#endif



static inline int rt_se_prio(struct sched_rt_entity *rt_se)
@@ -334,14 +430,13 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq) 


#ifdef CONFIG_SMP

	if (rt_rq->rt_time > runtime) {

		int more;



		spin_unlock(&rt_rq->rt_runtime_lock);

		more = balance_runtime(rt_rq);

		balance_runtime(rt_rq);

		spin_lock(&rt_rq->rt_runtime_lock);



		if (more)

		runtime = sched_rt_runtime(rt_rq);

		if (runtime == RUNTIME_INF)

			return 0;

	}

#endif
@@ -1174,6 +1269,8 @@ static void rq_online_rt(struct rq *rq) 
	if (rq->rt.overloaded)

		rt_set_overload(rq);



	__enable_runtime(rq);



	cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio);

}
@@ -1183,6 +1280,8 @@ static void rq_offline_rt(struct rq *rq) 
	if (rq->rt.overloaded)

		rt_clear_overload(rq);



	__disable_runtime(rq);



	cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_INVALID);

}

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