migration: add missing qemu_mutex_lock_iothread in migration_completion

qemu_savevm_state_complete_postcopy assumes the iothread lock (BQL)
to be held, but instead it isn't.

Signed-off-by: Emanuele Giuseppe Esposito <[email protected]>
Reviewed-by: Dr. David Alan Gilbert <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: esposem

migration/migration.c

@@ -3168,7 +3168,10 @@ static void migration_completion(MigrationState *s)
     } else if (s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
         trace_migration_completion_postcopy_end();
 
+        qemu_mutex_lock_iothread();
         qemu_savevm_state_complete_postcopy(s->to_dst_file);
+        qemu_mutex_unlock_iothread();
+
         trace_migration_completion_postcopy_end_after_complete();
     } else if (s->state == MIGRATION_STATUS_CANCELLING) {
         goto fail;