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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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.

thanks,

greg k-h