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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: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2011-01-23 12:09:36 +00:00
parent 1dbfa187da
commit 617912440b
1 changed files with 31 additions and 19 deletions
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50
arch/arm/kernel/irq.c
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@ -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 */