linux-kernel - Re: Rust kernel policy

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Message-ID: <20250219113331.17f014f4@gandalf.local.home>
Date: Wed, 19 Feb 2025 11:33:31 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Willy Tarreau <w@....eu>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, James Bottomley
 <James.Bottomley@...senPartnership.com>, "Martin K. Petersen"
 <martin.petersen@...cle.com>, Dan Carpenter <dan.carpenter@...aro.org>,
 Christoph Hellwig <hch@...radead.org>, Miguel Ojeda
 <miguel.ojeda.sandonis@...il.com>, rust-for-linux
 <rust-for-linux@...r.kernel.org>, Linus Torvalds
 <torvalds@...ux-foundation.org>, Greg KH <gregkh@...uxfoundation.org>,
 David Airlie <airlied@...il.com>, linux-kernel@...r.kernel.org,
 ksummit@...ts.linux.dev
Subject: Re: Rust kernel policy

On Wed, 19 Feb 2025 17:15:43 +0100
Willy Tarreau <w@....eu> wrote:

> Yeah absolutely. However I remember having faced code in the past where
> developers had abused this "unlock on return" concept resulting in locks
> lazily being kept way too long after an operation. I don't think this
> will happen in the kernel thanks to reviews, but typically all the stuff
> that's done after a locked retrieval was done normally is down outside
> of the lock, while here for the sake of not dealing with unlocks, quite
> a few lines were still covered by the lock for no purpose. Anyway
> there's no perfect solution.

This was one of my concerns, and it does creep up slightly (even in my own
use cases where I implemented them!).

But we should be encouraging the use of:

	scoped_guard(mutex)(&my_mutex) {
		/* Do the work needed for for my_mutex */
	}

Which does work out very well. And the fact that the code guarded by the
mutex is now also indented, it makes it easier to review.

-- Steve