Commit 3c18d447 authored by Juri Lelli's avatar Juri Lelli Committed by Ingo Molnar
Browse files

sched/core: Check for available DL bandwidth in cpuset_cpu_inactive() 



Hotplug operations are destructive w.r.t. cpusets. In case such an
operation is performed on a CPU belonging to an exlusive cpuset, the
DL bandwidth information associated with the corresponding root
domain is gone even if the operation fails (in sched_cpu_inactive()).

For this reason we need to move the check we currently have in
sched_cpu_inactive() to cpuset_cpu_inactive() to prevent useless
cpusets reconfiguration in the CPU_DOWN_FAILED path.

Signed-off-by: default avatarJuri Lelli <juri.lelli@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Link: http://lkml.kernel.org/r/1427792017-7356-2-git-send-email-juri.lelli@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4cd57f97

kernel/sched/core.c

+28 −28
Original line number Diff line number Diff line
@@ -5337,37 +5337,14 @@ static int sched_cpu_active(struct notifier_block *nfb, 
static int sched_cpu_inactive(struct notifier_block *nfb,

					unsigned long action, void *hcpu)

{

	unsigned long flags;

	long cpu = (long)hcpu;

	struct dl_bw *dl_b;



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_DOWN_PREPARE:

		set_cpu_active(cpu, false);



		/* explicitly allow suspend */

		if (!(action & CPU_TASKS_FROZEN)) {

			bool overflow;

			int cpus;



			rcu_read_lock_sched();

			dl_b = dl_bw_of(cpu);



			raw_spin_lock_irqsave(&dl_b->lock, flags);

			cpus = dl_bw_cpus(cpu);

			overflow = __dl_overflow(dl_b, cpus, 0, 0);

			raw_spin_unlock_irqrestore(&dl_b->lock, flags);



			rcu_read_unlock_sched();



			if (overflow)

				return notifier_from_errno(-EBUSY);

		}

		set_cpu_active((long)hcpu, false);

		return NOTIFY_OK;

	}



	default:

		return NOTIFY_DONE;

	}

}



static int __init migration_init(void)

{
@@ -7006,7 +6983,6 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action, 
		 */



	case CPU_ONLINE:

	case CPU_DOWN_FAILED:

		cpuset_update_active_cpus(true);

		break;

	default:
@@ -7018,8 +6994,32 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action, 
static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,

			       void *hcpu)

{

	switch (action) {

	unsigned long flags;

	long cpu = (long)hcpu;

	struct dl_bw *dl_b;



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_DOWN_PREPARE:

		/* explicitly allow suspend */

		if (!(action & CPU_TASKS_FROZEN)) {

			bool overflow;

			int cpus;



			rcu_read_lock_sched();

			dl_b = dl_bw_of(cpu);



			raw_spin_lock_irqsave(&dl_b->lock, flags);

			cpus = dl_bw_cpus(cpu);

			overflow = __dl_overflow(dl_b, cpus, 0, 0);

			raw_spin_unlock_irqrestore(&dl_b->lock, flags);



			rcu_read_unlock_sched();



			if (overflow) {

				trace_printk("hotplug failed for cpu %lu", cpu);

				return notifier_from_errno(-EBUSY);

			}

		}

		cpuset_update_active_cpus(false);

		break;

	case CPU_DOWN_PREPARE_FROZEN:

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