linux-kernel - Re: [PATCH 05/22] gpio: don't set label from irq helpers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACRpkdaEuJw5JfM0BUB9XKWe3jK_Urcce5MufLORc1c6gLLztA@mail.gmail.com>
Date: Wed, 31 Jan 2024 20:38:28 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Kent Gibson <warthog618@...il.com>, Alex Elder <elder@...aro.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, "Paul E . McKenney" <paulmck@...nel.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Wolfram Sang <wsa@...-dreams.de>, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 05/22] gpio: don't set label from irq helpers

On Tue, Jan 30, 2024 at 1:48 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> We will soon serialize access to the descriptor label using SRCU. The
> write-side of the protection will require calling synchronize_srcu()
> which must not be called from atomic context. We have two irq helpers:
> gpiochip_lock_as_irq() and gpiochip_unlock_as_irq() that set the label
> if the GPIO is not requested but is being used as interrupt. They are
> called with a spinlock held from the interrupt subsystem.
>
> They must not do it if we are to use SRCU so instead let's move the
> special corner case to a dedicated getter.
>
> Let's use the flags of the descriptor to figure out whether we should
> use the special "interrupt" label.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

I would refine the commit message: what you do IIUC is that you
simply avoid modifying a string, the label isn't set anymore,
instead a const string is returned and it is selected from the
state of an atomic variable (ha! smart!) and that is how the
atomicity is achieved.

Anyway:
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij