linux-kernel - Re: [PATCH v7 1/3] revocable: Revocable resource management

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Message-ID: <CAMRc=MfAZxzd2hjqgDsXBR+UxgkaEQX0vR5nNZ=a+5WccUb4GQ@mail.gmail.com>
Date: Fri, 16 Jan 2026 19:19:50 +0100
From: Bartosz Golaszewski <brgl@...nel.org>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, Tzung-Bi Shih <tzungbi@...nel.org>, 
	Benson Leung <bleung@...omium.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J . Wysocki" <rafael@...nel.org>, Linus Walleij <linusw@...nel.org>, Jonathan Corbet <corbet@....net>, 
	Shuah Khan <shuah@...nel.org>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	chrome-platform@...ts.linux.dev, linux-kselftest@...r.kernel.org, 
	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-gpio@...r.kernel.org
Subject: Re: [PATCH v7 1/3] revocable: Revocable resource management

On Fri, Jan 16, 2026 at 5:41 PM Danilo Krummrich <dakr@...nel.org> wrote:
>
> On Fri Jan 16, 2026 at 5:04 PM CET, Laurent Pinchart wrote:
> > Based on the discussions we had at LPC, the revocable resource management API
> > is not the right solution to handle races between device removal and userspace
> > access.
>
> Please see: https://lore.kernel.org/all/DFQ5D44A0348.PZJIGPL972N@kernel.org/
>
> > It is however a possibly useful tool for races between producers and consumers
> > *inside the kernel*.
>
> Do you have an example for such a case?

Isn't the GPIO use-case - which the series on top of it addresses - one?

With fw_devlink=off it's quite easy to trigger all kinds of crashes
with in-kernel users. I suggested using revocable in GPIO myself but I
won't accept it as long as it impacts performance over "naked" SRCU.

Bart