diff --git a/src/plugin/plugin_manager.cpp b/src/plugin/plugin_manager.cpp
index 5cf0797..49562b6 100644
--- a/src/plugin/plugin_manager.cpp
+++ b/src/plugin/plugin_manager.cpp
@@ -895,7 +895,7 @@ int stellar_packet_plugin_register(struct stellar *st, unsigned char ip_proto, p
 
 void plugin_manager_on_packet_ingress(struct plugin_manager_schema *plug_mgr, struct packet *pkt)
 {
-	if(plug_mgr->registered_packet_plugin_array == NULL || pkt == NULL)return;
+	if(plug_mgr==NULL || plug_mgr->registered_packet_plugin_array == NULL || pkt == NULL)return;
 	struct registered_packet_plugin_schema *p=NULL;
 
 	//TODO: get  innermost layer ip protocol by packet api
@@ -919,7 +919,7 @@ void plugin_manager_on_packet_ingress(struct plugin_manager_schema *plug_mgr, st
 
 void plugin_manager_on_packet_egress(struct plugin_manager_schema *plug_mgr, struct packet *pkt)
 {
-	if(plug_mgr->registered_packet_plugin_array == NULL || pkt == NULL)return;
+	if(plug_mgr == NULL || plug_mgr->registered_packet_plugin_array == NULL || pkt == NULL)return;
 	int tid=stellar_get_current_thread_index();
 	stellar_mq_dispatch(plug_mgr->per_thread_data[tid].priority_mq, &plug_mgr->per_thread_data[tid].dealth_letter_queue, NULL, pkt);
 	plug_mgr->per_thread_data[tid].pub_packet_msg_cnt=-1;//disable packet message publish
@@ -950,7 +950,7 @@ int stellar_polling_plugin_register(struct stellar *st, plugin_on_polling_func o
 
 int plugin_manager_on_polling(struct plugin_manager_schema *plug_mgr)
 {
-	if(plug_mgr->registered_polling_plugin_array == NULL)return 0;
+	if(plug_mgr==NULL || plug_mgr->registered_polling_plugin_array == NULL)return 0;
 	struct registered_polling_plugin_schema *p=NULL;
 	int polling_state=0;
 	while ((p = (struct registered_polling_plugin_schema *)utarray_next(plug_mgr->registered_polling_plugin_array, p)))
@@ -992,6 +992,7 @@ int stellar_session_plugin_register(struct stellar *st,
 
 void plugin_manager_on_session_ingress(struct session *sess, struct packet *pkt)
 {
+	if(sess==NULL)return;
 	struct plugin_manager_runtime *plug_mgr_rt = (struct plugin_manager_runtime *)session_get_user_data(sess);
 	if(plug_mgr_rt==NULL)return;
 #if 0	
@@ -1062,6 +1063,7 @@ void plugin_manager_on_session_ingress(struct session *sess, struct packet *pkt)
 
 void plugin_manager_on_session_egress(struct session *sess, struct packet *pkt)
 {
+	if(sess==NULL)return;
 	struct plugin_manager_runtime *plug_mgr_rt = (struct plugin_manager_runtime *)session_get_user_data(sess);
 	if(plug_mgr_rt==NULL)return;
 	plugin_manager_scratch_session_set(sess);
@@ -1076,6 +1078,7 @@ void plugin_manager_on_session_egress(struct session *sess, struct packet *pkt)
 
 void plugin_manager_on_session_closing(struct session *sess)
 {
+	if(sess==NULL)return;
 	struct plugin_manager_runtime *plug_mgr_rt = (struct plugin_manager_runtime *)session_get_user_data(sess);
 	if(plug_mgr_rt==NULL)return;
 	plug_mgr_rt->pub_session_msg_cnt=0;// reset pub_msg_cnt