>
> Since commit ef4b1bdb "red-channel-client: Prevent too tight loop
> waiting for ACKs", after seamless migration, the display is no longer
> updated on the client-side, even though the VM is functional (responds
> to keyboard input, reconnecting the client restores the display
> functionality, ...).
>
> This is mainly caused because after migration,
> red_channel_client_waiting_for_ack() will be true until
> red_channel_client_ack_zero_messages_window() is called.
>
> What happens is the following:
> The dcc is created, and dcc_start() pushes a RED_PIPE_ITEM_TYPE_SET_ACK
> message.
> This calls prepare_pipe_add(), which will enable write event on the dcc
> watch. red_channel_client_event() will be called, which will trigger a
> red_channel_client_push(). Since red_channel_client_waiting_for_ack()
> returns true, we won't get any item to push, and (because of commit
> ef4b1bdb), we will disable write notifications on the watch.
> At this point, rcc->priv->pipe is no longer empty, so prepare_pipe_add()
> is not going to reenable the write notifications.
>
> Then red_channel_client_ack_zero_messages_window() is finally called as
> part of dcc_handle_migrate_data(), so from this point on,
> red_channel_client_waiting_for_ack() is no longer true.
>
> However, nothing ever reenables WRITE events, nor empties
> rcc->priv->pipe, so nothing ever gets pushed, causing no display updates
> at all after a migration, even if the VM is functional (input, ...)
> apart from that.
>
> This commit reenables WRITE events in
> red_channel_client_ack_zero_messages_window() if we were waiting for
> ack.
>
> Signed-off-by: Christophe Fergeau <cfergeau@xxxxxxxxxx>
> ---
> server/red-channel-client.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/server/red-channel-client.c b/server/red-channel-client.c
> index bc1d0f3c4..967c93ed2 100644
> --- a/server/red-channel-client.c
> +++ b/server/red-channel-client.c
> @@ -1323,6 +1323,10 @@ void red_channel_client_push(RedChannelClient *rcc)
> while ((pipe_item = red_channel_client_pipe_item_get(rcc))) {
> red_channel_client_send_item(rcc, pipe_item);
> }
> + /* prepare_pipe_add() will reenable WRITE events when the
> rcc->priv->pipe is empty
> + * red_channel_client_ack_zero_messages_window() will reenable WRITE
> events
> + * if we were waiting for acks to be received
> + */
> if ((red_channel_client_no_item_being_sent(rcc) &&
> g_queue_is_empty(&rcc->priv->pipe)) ||
> red_channel_client_waiting_for_ack(rcc)) {
> red_channel_client_watch_update_mask(rcc, SPICE_WATCH_EVENT_READ);
> @@ -1671,6 +1675,10 @@ static void
> red_channel_client_pipe_clear(RedChannelClient *rcc)
>
> void red_channel_client_ack_zero_messages_window(RedChannelClient *rcc)
> {
> + if (red_channel_client_waiting_for_ack(rcc)) {
> + red_channel_client_watch_update_mask(rcc,
> +
> SPICE_WATCH_EVENT_READ|SPICE_WATCH_EVENT_WRITE);
> + }
> rcc->priv->ack_data.messages_window = 0;
> }
>
Looks good. I would remove the if condition.
Frediano
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