On Tue, Jul 09, 2013 at 02:10:45PM +0100, Neil Roberts wrote:
> If EOF is encountered while reading from the Wayland socket,
> wl_display_read_events() will now return -1 so that it will be treated
> as an error. The documentation for this function states that it will
> set errno when there is an error so it additionally makes up an errno
> of EPIPE.
Ah, yes, good catch. The multi-thread behaviour of
wl_display_read_events() allows mulitple threads to call into it, but
only one of the threads will get to read the data from the socket.
When I wrote this I was thinking that all other threads will call
recvmsg non-blocking and return 0 bytes. But 0 means "orderly
shutdown" of course, while -1 and errno = EAGAIN is "no data right
now". We do handle that case, but return -1, which the higher-level
code will treat as an error. I'll fix that in a follow-up commit.
> If we don't do this then when the compositor quits the Wayland socket
> will be become ready for reading but wl_display_dispatch will do
> nothing which typically makes the application take up 100% CPU. In
> particular eglSwapBuffers will likely get stuck in an infinite busy
> loop because it repeatedly calls wl_display_dispatch_queue while it
> waits for the frame callback.
Yes... I wonder why gtk+ doesn't handle POLLHUP and quits from that
though.
> ---
> src/wayland-client.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/src/wayland-client.c b/src/wayland-client.c
> index cb091ab..9400bcd 100644
> --- a/src/wayland-client.c
> +++ b/src/wayland-client.c
> @@ -877,6 +877,15 @@ read_events(struct wl_display *display)
> display_fatal_error(display, errno);
> return -1;
> }
> + else if (total == 0) {
> + /* The compositor has closed the socket. This
> + * should be considered an error so we'll fake
> + * an errno */
> + errno = EPIPE;
Yeah, EPIPE is fine I suppose.
thanks,
Kristian
> + display_fatal_error(display, errno);
> + return -1;
> + }
> +
> for (rem = total; rem >= 8; rem -= size) {
> size = queue_event(display, rem);
> if (size == -1) {
> --
> 1.7.11.3.g3c3efa5
>
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