[0.8 branch] server: add main_dispatcher

add main_dispatcher, a message passing mechanism for sending messages to
the main thread. The main thread is the thread that implements
SpiceCoreInterface, which is assumed to be a single thread.

Similar to the async operation of red_worker, a socket pair is created
and used to pass messages. The messages are a fixed size to ease
parsing. A single message is defined to pass a channel_event.

RHBZ: 746950
FDBZ: 41858

This patch is 0.8 branch only, for the master branch there should be a
better approach to share code with red_dispatcher and ready the way for
later adding more threads.

cherry-pick from 0.8 80caf07e09efe14c67f89a3c01501a6a39681167

Conflicts:

	server/reds.c

1 files changed, 3 insertions, 1 deletions

diff --git a/server/reds.c b/server/reds.c
index 90779ffb..65c98aef 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -56,6 +56,7 @@
 #include "main_channel.h"
 #include "red_common.h"
 #include "red_dispatcher.h"
+#include "main_dispatcher.h"
 #include "snd_worker.h"
 #include <spice/stats.h>
 #include "stat.h"
@@ -322,7 +323,7 @@ static void reds_stream_channel_event(RedsStream *s, int event)
 {
     if (core->base.minor_version < 3 || core->channel_event == NULL)
         return;
-    core->channel_event(event, &s->info);
+    main_dispatcher_channel_event(event, &s->info);
 }
 
 static ssize_t stream_write_cb(RedsStream *s, const void *buf, size_t size)
@@ -3519,6 +3520,7 @@ static int do_spice_init(SpiceCoreInterface *core_interface)
     init_vd_agent_resources();
     ring_init(&reds->clients);
     reds->num_clients = 0;
+    main_dispatcher_init(core);
 
     if (!(reds->mig_timer = core->timer_add(migrate_timout, NULL))) {
         red_error("migration timer create failed");