linux-kernel - Re: [PATCH v2 07/11] gpio: Add revocable provider handle for struct gpio

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Message-ID: <aYRaNu-ZistKBPN-@google.com>
Date: Thu, 5 Feb 2026 08:52:06 +0000
From: Tzung-Bi Shih <tzungbi@...nel.org>
To: Bartosz Golaszewski <brgl@...nel.org>
Cc: Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Jason Gunthorpe <jgg@...dia.com>, Johan Hovold <johan@...nel.org>,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	chrome-platform@...ts.linux.dev,
	Dan Williams <dan.j.williams@...el.com>, linux-gpio@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Linus Walleij <linusw@...nel.org>
Subject: Re: [PATCH v2 07/11] gpio: Add revocable provider handle for struct
 gpio_chip

On Wed, Feb 04, 2026 at 07:58:44AM -0500, Bartosz Golaszewski wrote:
> On Tue, 3 Feb 2026 07:10:54 +0100, Tzung-Bi Shih <tzungbi@...nel.org> said:
> > diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
> > index 3abb90385829..cd136d5b52e9 100644
> > --- a/drivers/gpio/gpiolib.h
> > +++ b/drivers/gpio/gpiolib.h
> > @@ -52,6 +52,7 @@
> >   * @device_notifier: used to notify character device wait queues about the GPIO
> >   *                   device being unregistered
> >   * @srcu: protects the pointer to the underlying GPIO chip
> > + * @chip_rp: revocable provider handle for the corresponding struct gpio_chip.
> >   * @pin_ranges: range of pins served by the GPIO driver
> >   *
> >   * This state container holds most of the runtime variable data
> > @@ -79,6 +80,7 @@ struct gpio_device {
> >  	struct workqueue_struct	*line_state_wq;
> >  	struct blocking_notifier_head device_notifier;
> >  	struct srcu_struct	srcu;
> > +	struct revocable_provider __rcu *chip_rp;
> >
> 
> Why __rcu? This doesn't live in a different address space, only the internal
> resource it protects does. If anything - this could be __attribute__((noderef))
> but even that is questionable as this is an opaque structure.

For fixing a race on the pointer itself.  See also [1].

[1] https://lore.kernel.org/all/20260129143733.45618-2-tzungbi@kernel.org