Re: gpiolib gpio_chrdev_release duration is about 30 ms

[Andy Shevchenko <andy.shevchenko@xxxxxxxxx>]

On Fri, Jul 17, 2020 at 5:17 PM Maxim Kochetkov <fido_max@xxxxxxxx> wrote:
>
> I need a small userspace program to do some GPIO magic to communicate
> other hardware like devmem. This program takes about 2,5 seconds just to
> find GPIO lines by name.
>
> replacing synchronize_rcu to synchronize_rcu_expedited in
> atomic_notifier_chain_unregister gives the same boost as removing
> synchronize_rcu

Have you tried to replace an atomic notifier call with a regular one?
IIRC it's still not clear why atomic is used there.

-- 
With Best Regards,
Andy Shevchenko