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

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Message-ID: <20250905134409.GD4067720@noisy.programming.kicks-ass.net>
Date: Fri, 5 Sep 2025 15:44:09 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Ard Biesheuvel <ardb@...nel.org>, Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH v2 5/7] arm64/efi: Use a semaphore to protect the EFI
 stack and FP/SIMD state

On Fri, Sep 05, 2025 at 03:30:41PM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.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?