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

Guilherme G. Piccoli
2022-08-07T15:39:07Z

On 19/07/2022 16:53, Guilherme G. Piccoli 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@kernel.org>
> Cc: David Gow <davidgow@google.com>
> Cc: Evan Green <evgreen@chromium.org>
> Cc: Julius Werner <jwerner@chromium.org>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
>
> ---
>
> V2:
> - do not use spin_trylock anymore, to avoid messing with
> non-panic paths; now we just check the spinlock state in
> the panic notifier before taking it. Thanks Evan for the
> review/idea!
>
> drivers/firmware/google/gsmi.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
> [...]

Hi Evan, do you think this one is good now, based on your previous review?

Appreciate any feedback!
Cheers,

Guilherme