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

[Jonas Ådahl]

On Fri, Jan 15, 2016 at 12:12:09AM +0000, Auke Booij wrote:
> 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

Fixed locally.

> 
> > 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)

The git history doesn't provide an explanation so I guess it is just a
mistake. I'll change the 2 to a 1 before pushing.


Jonas

> 
> > +
> > +       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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> > wayland-devel at lists.freedesktop.org
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