[PATCH v2 5/7] arm64/efi: Use a semaphore to protect the EFI stack and FP/SIMD state

[Ard Biesheuvel]

On Fri, 5 Sept 2025 at 15:44, Peter Zijlstra <peterz at infradead.org> wrote:
>
> On Fri, Sep 05, 2025 at 03:30:41PM +0200, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb at kernel.org>
> >
> > Replace the spinlock in the arm64 glue code with a semaphore, so that
> > the CPU can preempted while running the EFI runtime service.
>
> Gotta ask, why a semaphore and not a mutex?

Because mutex_trylock() is not permitted in interrupt context.