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 <redacted>
Cc: Evan Green <redacted>
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