linux-kernel - Re: [PATCH] gpiolib: extend the critical sections of lookup tables

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Message-ID: <CACRpkdYtbGqmMqN7FNhjYJGG+e0jWQmozf9kpNHiUBJvd2c=7Q@mail.gmail.com>
Date:   Wed, 20 Sep 2023 11:12:58 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH] gpiolib: extend the critical sections of lookup tables

On Wed, Sep 20, 2023 at 10:56 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>
> There are two places in the code where we retrieve a lookup table using
> gpiod_find_lookup_table() (which protects the table list with the lookup
> table lock) and then use it after the lock is released.
>
> We need to keep the lookup table mutex locked the entire time we're using
> the tables. Remove the locking from gpiod_find_lookup_table() and use
> guards to protect the code actually using the table objects.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

I convinced myself that this change is correct, good find!

> @@ -3822,8 +3822,6 @@ static struct gpiod_lookup_table *gpiod_find_lookup_table(struct device *dev)

Can we rename this function gpiod_find_lookup_table_locked()
as per precedents in the kernel, to indicate that it needs to be
called with a lock held?

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

Yours,
Linus Walleij