replay: checkpoints

This patch introduces checkpoints that synchronize cpu thread and iothread.
When checkpoint is met in the code all asynchronous events from the queue
are executed.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162444.8676.52916.stgit@PASHA-ISP.def.inno>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>

replay/replay.c

@@ -160,3 +160,37 @@ void replay_shutdown_request(void)
         replay_mutex_unlock();
     }
 }
+
+bool replay_checkpoint(ReplayCheckpoint checkpoint)
+{
+    bool res = false;
+    assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);
+    replay_save_instructions();
+
+    if (!replay_file) {
+        return true;
+    }
+
+    replay_mutex_lock();
+
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
+            replay_finish_event();
+        } else if (replay_data_kind != EVENT_ASYNC) {
+            res = false;
+            goto out;
+        }
+        replay_read_events(checkpoint);
+        /* replay_read_events may leave some unread events.
+           Return false if not all of the events associated with
+           checkpoint were processed */
+        res = replay_data_kind != EVENT_ASYNC;
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        replay_put_event(EVENT_CHECKPOINT + checkpoint);
+        replay_save_events(checkpoint);
+        res = true;
+    }
+out:
+    replay_mutex_unlock();
+    return res;
+}