Re: [PATCH v2 19/24] xtensa/cpu: Make sure cpu_die() doesn't return

Max Filippov
2023-02-14T19:48:56Z

On Tue, Feb 14, 2023 at 10:23 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> On Tue, Feb 14, 2023 at 08:55:32AM +0100, Philippe Mathieu-Daudé wrote:
> > Can you update the documentation along? Currently we have:
> >
> > /*
> > * Called from the idle thread for the CPU which has been shutdown.
> > *
> > * Note that we disable IRQs here, but do not re-enable them
> > * before returning to the caller. This is also the behaviour
> > * of the other hotplug-cpu capable cores, so presumably coming
> > * out of idle fixes this.
> > */
>
> void __ref cpu_die(void)
> {
> idle_task_exit();
> local_irq_disable();
> __asm__ __volatile__(
> " movi a2, cpu_restart\n"
> " jx a2\n");
>
> BUG();
> }
>
> Hm, not only is the comment wrong, but it seems to be branching to
> cpu_restart? That doesn't seem right at all.

Perhaps the name is a bit misleading. The CPU that enters 'cpu_restart'
loops there until a call to 'boot_secondary' releases it, after which it goes
to '_startup'. So it is a restart, but not immediate.

--
Thanks.
-- Max