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

[Guilherme G. Piccoli]

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@xxxxxxxxxx>
> Cc: David Gow <davidgow@xxxxxxxxxx>
> Cc: Evan Green <evgreen@xxxxxxxxxxxx>
> Cc: Julius Werner <jwerner@xxxxxxxxxxxx>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
> 
> ---
> 
> 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