linux-kernel - Re: [PATCH] gpio: virtio: remove timeout

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Date:   Mon, 20 Dec 2021 15:54:56 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     "Enrico Weigelt, metux IT consult" <info@...ux.net>,
        Viresh Kumar <vireshk@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>, kernel@...s.com,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpio: virtio: remove timeout

On Mon, Dec 20, 2021 at 2:07 PM Vincent Whitchurch
<vincent.whitchurch@...s.com> wrote:
>
> The driver imposes an arbitrary one second timeout on virtio requests,
> but the specification doesn't prevent the virtio device from taking
> longer to process requests, so remove this timeout to support all
> systems and device implementations.
>
> Fixes: 3a29355a22c0275fe86 ("gpio: Add virtio-gpio driver")
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
>  drivers/gpio/gpio-virtio.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/drivers/gpio/gpio-virtio.c b/drivers/gpio/gpio-virtio.c
> index 84f96b78f32a..9f4941bc5760 100644
> --- a/drivers/gpio/gpio-virtio.c
> +++ b/drivers/gpio/gpio-virtio.c
> @@ -100,11 +100,7 @@ static int _virtio_gpio_req(struct virtio_gpio *vgpio, u16 type, u16 gpio,
>         virtqueue_kick(vgpio->request_vq);
>         mutex_unlock(&vgpio->lock);
>
> -       if (!wait_for_completion_timeout(&line->completion, HZ)) {
> -               dev_err(dev, "GPIO operation timed out\n");
> -               ret = -ETIMEDOUT;
> -               goto out;
> -       }
> +       wait_for_completion(&line->completion);
>
>         if (unlikely(res->status != VIRTIO_GPIO_STATUS_OK)) {
>                 dev_err(dev, "GPIO request failed: %d\n", gpio);
> --
> 2.33.1
>

My knowledge of virtio is limited, I hope this is not a stupid question.

Does this mean the operation can get stuck indefinitely?

Bart