linux-kernel - Re: [PATCH v2 0/3] Revert "revocable: Revocable resource management"

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Message-ID: <aYdFle_Un6du3FZS@tzungbi-laptop>
Date: Sat, 7 Feb 2026 22:00:53 +0800
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Johan Hovold <johan@...nel.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Bartosz Golaszewski <bartosz.golaszewski@....qualcomm.com>,
	Linus Walleij <linusw@...nel.org>, Jonathan Corbet <corbet@....net>,
	Shuah Khan <shuah@...nel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Simona Vetter <simona.vetter@...ll.ch>,
	Dan Williams <dan.j.williams@...el.com>,
	Jason Gunthorpe <jgg@...dia.com>, linux-doc@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] Revert "revocable: Revocable resource management"

On Fri, Feb 06, 2026 at 04:13:00PM +0100, Greg Kroah-Hartman wrote:
> On Wed, Feb 04, 2026 at 03:28:46PM +0100, Johan Hovold wrote:
> > I was surprised to learn that the revocable functionality was merged the other
> > week given the community feedback on list and at LPC, but not least since there
> > are no users of it, which we are supposed to require to be able to evaluate it
> > properly.
> > 
> > The chromeos ec driver issue which motivated this work turned out not to need
> > it as was found during review. And the example gpiolib conversion was posted
> > the very same morning that this was merged which hardly provides enough time
> > for evaluation (even if Bartosz quickly reported a performance regression).
> > 
> > Turns out there are correctness issues with both the gpiolib conversion and
> > the revocable design itself that can lead to use-after-free and hung tasks (see
> > [1] and [2]).
> > 
> > And as was pointed out repeatedly during review, and again at the day of the
> > merge, this does not look like the right interface for the chardev unplug
> > issue.
> > 
> > Despite the last-minute attempt at addressing the issues mentioned above
> > incrementally, the revocable design is still fundamentally flawed (see patch
> > 3/3).
> > 
> > We have processes like requiring a user before merging a new interface so that
> > issues like these can be identified and the soundness of an API be evaluated.
> > They also give a sense of when things are expected to happen, which allows our
> > scarce reviewers to manage their time (e.g. to not be forced to drop everything
> > else they are doing when things are merged prematurely).
> > 
> > There really is no reason to exempt any new interface from this regardless of
> > whether one likes the underlying concept or not.
> > 
> > Revert the revocable implementation until a redesign has been proposed and
> > evaluated properly.
> 
> After thinking about this a lot, and talking it over with Danilo a bit,
> I've applied this series that reverts these changes.
> 
> Kernel developers / maintainers are only "allowed" one major argument /
> fight a year, and I really don't want to burn my 2026 usage so early in
> the year :)
> 
> Tzung-Bi, can you take the feedback here, and what you have learned from
> the gpio patch series, and rework this into a "clean" patch series for
> us to review and comment on for future releases?  That should give us
> all a baseline on which to work off of, without having to worry about
> the different versions/fixes floating around at the moment.

Acknowledged.  I'll start reworking this into a unified series that
incorporates the feedback and lessons learned.