linux-kernel - Re: [PATCH] arm64: kgdb: Ensure atomic single-step execution

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Message-ID: <aOZIusaX-fpeLAz4@J2N7QTR9R3>
Date: Wed, 8 Oct 2025 12:19:22 +0100
From: Mark Rutland <mark.rutland@....com>
To: Li Mengchen <mengchenli64@...il.com>
Cc: catalin.marinas@....com, will@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: kgdb: Ensure atomic single-step execution

On Wed, Oct 08, 2025 at 09:01:22AM +0800, Li Mengchen wrote:
> I am writing to address a persistent issue in the community’s code
> related to single-step tracing, which has remained unresolved for over
> a decade. The code I have provided has been extensively tested and
> proven to work across multiple hardware platforms and kernel versions,
> from 3.10 to the latest releases. Its correctness and effectiveness
> are not up for debate.

There is no debate; it is a statement of fact that those changes are
incomplete (e.g. failing to address other asynchronous exceptions),
incorrect (e.g. erroneously *unmasking* interrupts in some cases), and
contain unjustified changes which are themselves incorrect (e.g. using
task_pt_regs(), which *never* contains kernel register state).

I appreciate that those changes may be sufficient in the scenarios that
you have tested, but as I have already commented (with examples), there
are real scenarios where those changes make matters worse.

I agree that there are some longstanding issues here, but (as-is) the
changes you have proposed are not a suitable solution.

Mark.