Re: [PATCH v3 01/24] gpio: protect the list of GPIO devices with SRCU

Bartosz Golaszewski
2024-02-10T11:07:51Z

On Sat, Feb 10, 2024 at 12:01 PM Hillf Danton <hdanton@sina.com> wrote:
>
> On Thu, 8 Feb 2024 10:58:57 +0100 Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > @@ -382,11 +389,13 @@ static int gpiodev_add_to_list_unlocked(struct gpio_device *gdev)
> > /* add between prev and next */
> > if (prev->base + prev->ngpio <= gdev->base
> > && gdev->base + gdev->ngpio <= next->base) {
> > - list_add(&gdev->list, &prev->list);
> > + list_add_rcu(&gdev->list, &prev->list);
> > return 0;
> > }
> > }
> >
> > + synchronize_srcu(&gpio_devices_srcu);
> > +
> If not typo, could you shed light on why this sync is needed?
>

No it's not a typo. I'm not an expert on RCU but I figured that right
after we add the new element to the SRCU-protected list, we need to
wait for all read-only critical sections to complete before
continuing? Is that not correct?

Bart

> > return -EBUSY;
> > }
>