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SubjectRe: [PATCH] IRQ, cpu-hotplug: Fix a race between CPU hotplug and IRQ desc alloc/free
On Mon, 4 Sep 2017, Huang, Ying wrote:
> diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
> index 638eb9c83d9f..af9029625271 100644
> --- a/kernel/irq/cpuhotplug.c
ry> +++ b/kernel/irq/cpuhotplug.c
> @@ -129,10 +129,13 @@ void irq_migrate_all_off_this_cpu(void)
> struct irq_desc *desc;
> unsigned int irq;
>
> + irq_lock_sparse();

You cannot take that lock here as irq_migrate_all_off_this_cpu() is called
with interrupts disabled.

The protection in takedown_cpus() is wrong. Patch below.

Thanks,

tglx
----

--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -642,13 +642,13 @@ static int takedown_cpu(unsigned int cpu
wait_for_completion(&st->done);
BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);

- /* Interrupts are moved away from the dying cpu, reenable alloc/free */
- irq_unlock_sparse();
-
hotplug_cpu__broadcast_tick_pull(cpu);
/* This actually kills the CPU. */
__cpu_die(cpu);

+ /* Interrupts are moved away from the dying cpu, reenable alloc/free */
+ irq_unlock_sparse();
+
tick_cleanup_dead_cpu(cpu);
return 0;
}

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