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dcc: Fix seamless migration

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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waiting for ACKs", after seamless migration, the display is no longer
updated on the client-side, even though the VM is functional (responds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@redhat.com>
This commit is contained in:
Christophe Fergeau 2017-10-05 13:53:49 +02:00
parent 8705e3d123
commit 657a1d92e8
1 changed files with 6 additions and 0 deletions
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6
server/red-channel-client.c
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@ -1327,6 +1327,10 @@ 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);
@ -1677,6 +1681,8 @@ static void red_channel_client_pipe_clear(RedChannelClient *rcc)
void red_channel_client_ack_zero_messages_window(RedChannelClient *rcc)
{
red_channel_client_watch_update_mask(rcc,
SPICE_WATCH_EVENT_READ|SPICE_WATCH_EVENT_WRITE);
rcc->priv->ack_data.messages_window = 0;
}