Quoting Evan Green (2020-09-29 13:30:57)
> smp2p_update_bits() should disable interrupts when it acquires its
> spinlock. This is important because without the _irqsave, a priority
> inversion can occur.
>
> This function is called both with interrupts enabled in
> qcom_q6v5_request_stop(), and with interrupts disabled in
> ipa_smp2p_panic_notifier(). IRQ handling of spinlocks should be
> consistent to avoid the panic notifier deadlocking because it's
> sitting on the thread that's already got the lock via _request_stop().
>
> Found via lockdep.
>
> Fixes: 50e99641413e7 ("soc: qcom: smp2p: Qualcomm Shared Memory Point to
> Point")
> Signed-off-by: Evan Green <[email protected]>
> ---
Reviewed-by: Stephen Boyd <[email protected]>
