[PATCH wayland v2] client: Fully flush during blocking dispatch

[Auke Booij]

On 12 January 2016 at 04:31, Jonas Ådahl <jadahl at gmail.com> wrote:
> wl_display_flush() may fail with EAGAIN which means that not all data
> waiting in the buffer has been flushed. We later block until there

+ is

> data to read, which could mean that we block on input from the
> compositor without having sent out all data from the client. Avoid this
> by fully flushing the socket before starting to wait.
>
> Signed-off-by: Jonas Ådahl <jadahl at gmail.com>
> ---
>  src/wayland-client.c | 39 +++++++++++++++++++++++++++++----------
>  1 file changed, 29 insertions(+), 10 deletions(-)
>
> diff --git a/src/wayland-client.c b/src/wayland-client.c
> index 8bf6124..f47e395 100644
> --- a/src/wayland-client.c
> +++ b/src/wayland-client.c
> @@ -1442,6 +1442,21 @@ wl_display_cancel_read(struct wl_display *display)
>         pthread_mutex_unlock(&display->mutex);
>  }
>
> +static int
> +wl_display_poll(struct wl_display *display, short int events)
> +{
> +       int ret;
> +       struct pollfd pfd[2];

why 2? why an array at all? why not just

struct pollfd pfd;
pfd.fd = display->fd;
pfd.events = events;
do {
  poll(&pfd, 1, -1);
} while (blabla);

(i understand this was in the original as well and you're simply
moving code around)

> +
> +       pfd[0].fd = display->fd;
> +       pfd[0].events = events;
> +       do {
> +               ret = poll(pfd, 1, -1);
> +       } while (ret == -1 && errno == EINTR);
> +
> +       return ret;
> +}
> +
>  /** Dispatch events in an event queue
>   *
>   * \param display The display context object
> @@ -1485,27 +1500,31 @@ WL_EXPORT int
>  wl_display_dispatch_queue(struct wl_display *display,
>                           struct wl_event_queue *queue)
>  {
> -       struct pollfd pfd[2];
>         int ret;
>
>         if (wl_display_prepare_read_queue(display, queue) == -1)
>                 return wl_display_dispatch_queue_pending(display, queue);
>
> +       while (true) {
> +               ret = wl_display_flush(display);
> +               if (ret == -1 && errno == EAGAIN) {
> +                       if (wl_display_poll(display, POLLOUT) == -1) {
> +                               wl_display_cancel_read(display);
> +                               return -1;
> +                       }
> +               } else {
> +                       break;
> +               }
> +       }
> +
>         /* Don't stop if flushing hits an EPIPE; continue so we can read any
>          * protocol error that may have triggered it. */
> -       ret = wl_display_flush(display);
> -       if (ret < 0 && errno != EAGAIN && errno != EPIPE) {
> +       if (ret < 0 && errno != EPIPE) {
>                 wl_display_cancel_read(display);
>                 return -1;
>         }
>
> -       pfd[0].fd = display->fd;
> -       pfd[0].events = POLLIN;
> -       do {
> -               ret = poll(pfd, 1, -1);
> -       } while (ret == -1 && errno == EINTR);
> -
> -       if (ret == -1) {
> +       if (wl_display_poll(display, POLLIN) == -1) {
>                 wl_display_cancel_read(display);
>                 return -1;
>         }
> --
> 2.4.3
>
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