linux-kernel - Re: [patch 0/4] uaccess: Provide and use helpers for user masked access

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Message-ID: <aKPj4_-3wNu2v4J2@casper.infradead.org>
Date: Tue, 19 Aug 2025 03:39:31 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: David Laight <david.laight.linux@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	André Almeida <andrealmeid@...lia.com>,
	x86@...nel.org, Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [patch 0/4] uaccess: Provide and use helpers for user masked
 access

On Mon, Aug 18, 2025 at 02:36:31PM -0700, Linus Torvalds wrote:
> I realize some people have grown up being told that "goto is bad". Or
> have been told that exception handling should be baked into the
> language and be asynchronous. Both of those ideas are complete and
> utter garbage, and the result of minds that cannot comprehend reality.
> 
> Asynchronous exceptions are horrific and tend to cause huge
> performance problems (think setjmp()). The Linux kernel exception
> model with explicit exception points is not only "that's how you have
> to do it in C", it's also technically superior.
> 
> And "goto" is fine, as long as you have legible syntax and don't use
> it to generate spaghetti code. Being able to write bad code with goto
> doesn't make 'goto' bad - you can write bad code with *anything*.

Even Dijkstra doesn't argue against using goto for exception handling,

"I remember having read the explicit recommendation to restrict the use
of the go to statement to alarm exits, but I have not been able to trace
it; presumably, it has been made by C.A.R. Hoare."

https://www.cs.utexas.edu/~EWD/transcriptions/EWD02xx/EWD215.html