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

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Date: Wed, 14 Feb 2024 14:22:17 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Mark Brown <broonie@...nel.org>
Cc: Linus Walleij <linus.walleij@...aro.org>, 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>, 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 2:17 PM Mark Brown <broonie@...nel.org> wrote:
>
> 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.
>
> This doesn't fix the issue I reported yesterday when applied on top of
> today's next:
>
>    https://lava.sirena.org.uk/scheduler/job/585469
>
> [    1.995518] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000078
>
> ...
>
> [    2.176162] Call trace:
> [    2.178610]  check_init_srcu_struct+0x1c/0xa0
> [    2.182974]  synchronize_srcu+0x1c/0x100
> [    2.186904]  gpiod_request_commit+0xec/0x1e0
> [    2.191183]  gpiochip_request_own_desc+0x58/0x124
> [    2.195894]  gpiod_hog+0x114/0x1b4
> [    2.199305]  of_gpiochip_add+0x208/0x370
> [    2.203232]  gpiochip_add_data_with_key+0x71c/0xf10
> [    2.208117]  devm_gpiochip_add_data_with_key+0x30/0x7c
> [    2.213261]  mxc_gpio_probe+0x208/0x4b0

No, the fix for this issue is in my tree as commit ba5c5effe02c
("gpio: initialize descriptor SRCU structure before adding OF-based
chips"). These are mostly fixes for lockdep warnings.

Bart