[PATCH] server: Add API to disable the event queue

[Pekka Paalanen]

On Fri, 13 Sep 2013 16:12:27 +0100
Neil Roberts <neil at linux.intel.com> wrote:

> Adds wl_client_disable_queue and wl_client_enable_queue. When the
> queue is disabled, flushing the client will cause it to send all of
> the data regardless of whether ‘want_flush’ is set on the connection.
> 
> The ‘want_flush’ mechanism is used to implement the event queue.
> Normally queued events are only sent once a later event is posted
> without the queue. It looks like this is currently only used in order
> to delay sending the buffer release events until a frame callback
> event is emitted at the same time to avoid waking up the clients more
> often than necessary.
> 
> The problem with that is that if a client isn't using the frame
> callbacks and instead is throttling itself to the buffer release
> events then the queue will never get flushed and the client will wait
> forever. With this new API the compositor can recognise when a client
> doesn't have a frame callback installed and explicitly disable the
> queue so that it will get the buffer release events immediately.

Instead of all this, could you not have made Weston simply use
wl_resource_post_event() instead of wl_resource_queue_event()?

Btw. enable/disable_queue sounds like you would be freezing or thawing
a wl_queue or something like that.

Better wait for other comments, whether changing the release event
sending method is acceptable.


Thanks,
pq

> ---
>  src/connection.c      | 16 +++++++++++++++-
>  src/wayland-private.h |  2 ++
>  src/wayland-server.c  | 12 ++++++++++++
>  src/wayland-server.h  |  2 ++
>  4 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/src/connection.c b/src/connection.c
> index 451b93e..5e26af1 100644
> --- a/src/connection.c
> +++ b/src/connection.c
> @@ -59,6 +59,7 @@ struct wl_connection {
>  	struct wl_buffer fds_in, fds_out;
>  	int fd;
>  	int want_flush;
> +	int enable_queue;
>  };
>  
>  static void
> @@ -157,6 +158,7 @@ wl_connection_create(int fd)
>  		return NULL;
>  	memset(connection, 0, sizeof *connection);
>  	connection->fd = fd;
> +	connection->enable_queue = 1;
>  
>  	return connection;
>  }
> @@ -265,7 +267,7 @@ wl_connection_flush(struct wl_connection *connection)
>  	int len = 0, count, clen;
>  	uint32_t tail;
>  
> -	if (!connection->want_flush)
> +	if (connection->enable_queue && !connection->want_flush)
>  		return 0;
>  
>  	tail = connection->out.tail;
> @@ -372,6 +374,18 @@ wl_connection_queue(struct wl_connection *connection,
>  	return 0;
>  }
>  
> +void
> +wl_connection_enable_queue(struct wl_connection *connection)
> +{
> +	connection->enable_queue = 1;
> +}
> +
> +void
> +wl_connection_disable_queue(struct wl_connection *connection)
> +{
> +	connection->enable_queue = 0;
> +}
> +
>  static int
>  wl_message_count_arrays(const struct wl_message *message)
>  {
> diff --git a/src/wayland-private.h b/src/wayland-private.h
> index 67e8783..6247cee 100644
> --- a/src/wayland-private.h
> +++ b/src/wayland-private.h
> @@ -92,6 +92,8 @@ void wl_connection_consume(struct wl_connection *connection, size_t size);
>  
>  int wl_connection_flush(struct wl_connection *connection);
>  int wl_connection_read(struct wl_connection *connection);
> +void wl_connection_enable_queue(struct wl_connection *connection);
> +void wl_connection_disable_queue(struct wl_connection *connection);
>  
>  int wl_connection_write(struct wl_connection *connection, const void *data, size_t count);
>  int wl_connection_queue(struct wl_connection *connection,
> diff --git a/src/wayland-server.c b/src/wayland-server.c
> index d7c58b9..6d37137 100644
> --- a/src/wayland-server.c
> +++ b/src/wayland-server.c
> @@ -591,6 +591,18 @@ wl_client_get_destroy_listener(struct wl_client *client,
>  }
>  
>  WL_EXPORT void
> +wl_client_enable_queue(struct wl_client *client)
> +{
> +	wl_connection_enable_queue(client->connection);
> +}
> +
> +WL_EXPORT void
> +wl_client_disable_queue(struct wl_client *client)
> +{
> +	wl_connection_disable_queue(client->connection);
> +}
> +
> +WL_EXPORT void
>  wl_client_destroy(struct wl_client *client)
>  {
>  	uint32_t serial = 0;
> diff --git a/src/wayland-server.h b/src/wayland-server.h
> index 67f3bdd..95a1ae2 100644
> --- a/src/wayland-server.h
> +++ b/src/wayland-server.h
> @@ -123,6 +123,8 @@ void wl_client_add_destroy_listener(struct wl_client *client,
>  				    struct wl_listener *listener);
>  struct wl_listener *wl_client_get_destroy_listener(struct wl_client *client,
>  						   wl_notify_func_t notify);
> +void wl_client_enable_queue(struct wl_client *client);
> +void wl_client_disable_queue(struct wl_client *client);
>  
>  struct wl_resource *
>  wl_client_get_object(struct wl_client *client, uint32_t id);