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Commit 61791244 authored by Russell King's avatar Russell King
Browse files

ARM: irq migration: ensure migration is handled safely 



Ensure appropriate locks are taken to ensure that IRQ migration off
the current CPU is race-free.  We may have a concurrent set_affinity
via procfs running on another CPU in parallel with the IRQ migration,
resulting in unpredictable results.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 1dbfa187

arch/arm/kernel/irq.c

+31 −19
Original line number Diff line number Diff line
@@ -179,14 +179,21 @@ int __init arch_probe_nr_irqs(void) 


#ifdef CONFIG_HOTPLUG_CPU



static void route_irq(struct irq_desc *desc, unsigned int irq, unsigned int cpu)

static bool migrate_one_irq(struct irq_data *d)

{

	pr_debug("IRQ%u: moving from cpu%u to cpu%u\n", irq, desc->irq_data.node, cpu);

	unsigned int cpu = cpumask_any_and(d->affinity, cpu_online_mask);

	bool ret = false;



	raw_spin_lock_irq(&desc->lock);

	desc->irq_data.chip->irq_set_affinity(&desc->irq_data,

					      cpumask_of(cpu), true);

	raw_spin_unlock_irq(&desc->lock);

	if (cpu >= nr_cpu_ids) {

		cpu = cpumask_any(cpu_online_mask);

		ret = true;

	}



	pr_debug("IRQ%u: moving from cpu%u to cpu%u\n", d->irq, d->node, cpu);



	d->chip->irq_set_affinity(d, cpumask_of(cpu), true);



	return ret;

}



/*
@@ -198,25 +205,30 @@ void migrate_irqs(void) 
{

	unsigned int i, cpu = smp_processor_id();

	struct irq_desc *desc;

	unsigned long flags;



	local_irq_save(flags);



	for_each_irq_desc(i, desc) {

		struct irq_data *d = &desc->irq_data;

		bool affinity_broken = false;



		if (d->node == cpu) {

			unsigned int newcpu = cpumask_any_and(d->affinity,

							      cpu_online_mask);

			if (newcpu >= nr_cpu_ids) {

				if (printk_ratelimit())

					printk(KERN_INFO "IRQ%u no longer affine to CPU%u\n",

					       i, cpu);

		raw_spin_lock(&desc->lock);

		do {

			if (desc->action == NULL)

				break;



				cpumask_setall(d->affinity);

				newcpu = cpumask_any_and(d->affinity,

							 cpu_online_mask);

			}

			if (d->node != cpu)

				break;



			route_irq(desc, i, newcpu);

		}

			affinity_broken = migrate_one_irq(d);

		} while (0);

		raw_spin_unlock(&desc->lock);



		if (affinity_broken && printk_ratelimit())

			pr_warning("IRQ%u no longer affine to CPU%u\n", i, cpu);

	}



	local_irq_restore(flags);

}

#endif /* CONFIG_HOTPLUG_CPU */