add migration state change notifiers

This patch adds functions to register and unregister notifiers for
migration state changes and a function to query the migration state.
The notifier is called on every state change.  Once after establishing a
new migration object (which is in active state then) and once when the
state changes from active to completed, canceled or error.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

migration.c

@@ -36,6 +36,9 @@ static int64_t max_throttle = (32 << 20);
 
 static MigrationState *current_migration;
 
+static NotifierList migration_state_notifiers =
+    NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);
+
 int qemu_start_incoming_migration(const char *uri)
 {
     const char *p;
@@ -121,6 +124,7 @@ int do_migrate(Monitor *mon, const QDict *qdict, QObject **ret_data)
     }
 
     current_migration = s;
+    notifier_list_notify(&migration_state_notifiers);
     return 0;
 }
 
@@ -272,6 +276,7 @@ void migrate_fd_error(FdMigrationState *s)
 {
     DPRINTF("setting error state\n");
     s->state = MIG_STATE_ERROR;
+    notifier_list_notify(&migration_state_notifiers);
     migrate_fd_cleanup(s);
 }
 
@@ -329,6 +334,7 @@ ssize_t migrate_fd_put_buffer(void *opaque, const void *data, size_t size)
             monitor_resume(s->mon);
         }
         s->state = MIG_STATE_ERROR;
+        notifier_list_notify(&migration_state_notifiers);
     }
 
     return ret;
@@ -389,6 +395,7 @@ void migrate_fd_put_ready(void *opaque)
             state = MIG_STATE_ERROR;
         }
         s->state = state;
+        notifier_list_notify(&migration_state_notifiers);
     }
 }
 
@@ -408,6 +415,7 @@ void migrate_fd_cancel(MigrationState *mig_state)
     DPRINTF("cancelling migration\n");
 
     s->state = MIG_STATE_CANCELLED;
+    notifier_list_notify(&migration_state_notifiers);
     qemu_savevm_state_cancel(s->mon, s->file);
 
     migrate_fd_cleanup(s);
@@ -421,6 +429,7 @@ void migrate_fd_release(MigrationState *mig_state)
    
     if (s->state == MIG_STATE_ACTIVE) {
         s->state = MIG_STATE_CANCELLED;
+        notifier_list_notify(&migration_state_notifiers);
         migrate_fd_cleanup(s);
     }
     qemu_free(s);
@@ -452,3 +461,22 @@ int migrate_fd_close(void *opaque)
     qemu_set_fd_handler2(s->fd, NULL, NULL, NULL, NULL);
     return s->close(s);
 }
+
+void add_migration_state_change_notifier(Notifier *notify)
+{
+    notifier_list_add(&migration_state_notifiers, notify);
+}
+
+void remove_migration_state_change_notifier(Notifier *notify)
+{
+    notifier_list_remove(&migration_state_notifiers, notify);
+}
+
+int get_migration_state(void)
+{
+    if (current_migration) {
+        return migrate_fd_get_status(current_migration);
+    } else {
+        return MIG_STATE_ERROR;
+    }
+}

migration.h

@@ -16,6 +16,7 @@
 
 #include "qdict.h"
 #include "qemu-common.h"
+#include "notify.h"
 
 #define MIG_STATE_ERROR		-1
 #define MIG_STATE_COMPLETED	0
@@ -134,4 +135,8 @@ static inline FdMigrationState *migrate_to_fms(MigrationState *mig_state)
     return container_of(mig_state, FdMigrationState, mig_state);
 }
 
+void add_migration_state_change_notifier(Notifier *notify);
+void remove_migration_state_change_notifier(Notifier *notify);
+int get_migration_state(void);
+
 #endif