Re: [PATCH v2 03/13] firmware: google: Test spinlock on panic path to avoid lockups

[Evan Green]

On Tue, Jul 19, 2022 at 12:55 PM Guilherme G. Piccoli
<gpiccoli@xxxxxxxxxx> wrote:
>
> Currently the gsmi driver registers a panic notifier as well as
> reboot and die notifiers. The callbacks registered are called in
> atomic and very limited context - for instance, panic disables
> preemption and local IRQs, also all secondary CPUs (not executing
> the panic path) are shutdown.
>
> With that said, taking a spinlock in this scenario is a dangerous
> invitation for lockup scenarios. So, fix that by checking if the
> spinlock is free to acquire in the panic notifier callback - if not,
> bail-out and avoid a potential hang.
>
> Fixes: 74c5b31c6618 ("driver: Google EFI SMI")
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: David Gow <davidgow@xxxxxxxxxx>
> Cc: Evan Green <evgreen@xxxxxxxxxxxx>
> Cc: Julius Werner <jwerner@xxxxxxxxxxxx>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>

Reviewed-by: Evan Green <evgreen@xxxxxxxxxxxx>