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

[Peter Zijlstra]

On Fri, Sep 05, 2025 at 03:54:55PM +0200, Ard Biesheuvel wrote:
> 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.

Ah, true. Might make for a good comment near there.