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

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Date:   Wed, 20 Sep 2023 05:51:56 -0700
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH] gpiolib: extend the critical sections of lookup tables

On Wed, 20 Sep 2023 12:58:58 +0200, Linus Walleij
<linus.walleij@...aro.org> said:
> On Wed, Sep 20, 2023 at 11:33 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>> On Wed, 20 Sep 2023 11:12:58 +0200, Linus Walleij
>> <linus.walleij@...aro.org> said:
>> > On Wed, Sep 20, 2023 at 10:56 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
>> > 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?
>> >
>>
>> I think you mean gpiod_find_lookup_table_unlocked() as with this change it
>> will no longer take the lock?
>
> I think the pattern is the one I indicated: *_locked() means the function
> is to be called with the appropriate lock held, cf
> arch/arm64/kvm/hyp/nvhe/mm.c
>
> pkvm_create_mappings() takes a lock and then calls
> pkvm_create_mappings_locked() which even asserts that
> the lock is held.
>

Ha! I always though the pattern is to call the functions that *DON'T* take
the lock _unlocked(). This is what I used in gpiolib-cdev.c or gpio-sim.c.

I guess both conventions make sense in some way.

Bart