On Mon, Aug 31, 2015 at 01:04:33PM -0500, Alex Thorlton wrote:
q
> diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
> index fd643d8..8502521 100644
> --- a/kernel/stop_machine.c
> +++ b/kernel/stop_machine.c
> @@ -417,8 +417,11 @@ static void cpu_stopper_thread(unsigned int cpu)
> {
> struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
> struct cpu_stop_work *work;
> + unsigned long flags;
> int ret;
>
> + local_irq_save(flags);
> +
> repeat:
> work = NULL;
> spin_lock_irq(&stopper->lock);
> @@ -452,6 +455,8 @@ repeat:
> cpu_stop_signal_done(done, true);
> goto repeat;
> }
> +
> + local_irq_restore(flags);
> }
>
So I should probably just go sleep and not say anything.. _but_
*confused*.
That local_irq_save() will disable IRQs over:
work = NULL;
But that is _all_. The spin_unlock_irq() will re-enable IRQs, after
which things will run as usual.
That local_irq_restore() is a total NOP, IRQs are guaranteed enabled at
the irq_local_save() (otherwise lockdep would've complained about
spin_unlock_irq() unconditionally enabling them) and by the time we get
to the restore that same unlock_irq will have enabled them already.
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