linux-kernel - Re: [PATCH v2 0/4] gpio: fix SRCU bugs

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Date: Wed, 14 Feb 2024 10:44:36 -0800
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Kent Gibson <warthog618@...il.com>, Alex Elder <elder@...aro.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>, Mark Brown <broonie@...nel.org>,
	Dan Carpenter <dan.carpenter@...aro.org>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 0/4] gpio: fix SRCU bugs

On Wed, Feb 14, 2024 at 09:44:15AM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> 
> Here are four fixes to some bugs in recent SRCU changes. The first one fixes
> an actual race condition. The other three just make lockdep happy.

For 1/4-3/4:

Acked-by: Paul E. McKenney <paulmck@...nel.org>

For 4/4, you are playing with fire, but I will assume that you know what
you are doing.  ;-)

							Thanx, Paul

> v1 -> v2:
> - use srcu_dereference() instead of rcu_dereference_protected() as
>   advised by Paul
> - add a patch using rcu_dereference_check(..., 1) in deprecated
>   interfaces that return the address of the RCU-protected chip structure
>   to external users (who shouldn't use it anyway but well...)
> - pick up review tags for patches 1/4 and 2/4
> 
> Bartosz Golaszewski (4):
>   gpio: take the SRCU read lock in gpiod_hog()
>   gpio: cdev: use correct pointer accessors with SRCU
>   gpio: use srcu_dereference() with SRCU-protected pointers
>   gpio: don't let lockdep complain about inherently dangerous RCU usage
> 
>  drivers/gpio/gpiolib-cdev.c  | 25 ++++++++++++-------------
>  drivers/gpio/gpiolib-sysfs.c |  5 +++--
>  drivers/gpio/gpiolib.c       | 32 ++++++++++++++++++--------------
>  drivers/gpio/gpiolib.h       |  3 ++-
>  4 files changed, 35 insertions(+), 30 deletions(-)
> 
> -- 
> 2.40.1
>