MDEV-6497 InnoDB deadlocks on UNINSTALL PLUGIN

Free the trx of the current thd (if any) in innobase_end()

mysql-test/r/innodb_load_xa.result

@@ -4,4 +4,17 @@ Warning	1105	Cannot enable tc-log at run-time. XA features of InnoDB are disable
 select engine,support,transactions,xa from information_schema.engines where engine='innodb';
 engine	support	transactions	xa
 InnoDB	YES	YES	NO
+create table t1 (a int) engine=innodb;
+start transaction;
+insert t1 values (1);
+insert t1 values (2);
+commit;
+show binlog events from <binlog_start>;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+mysqld-bin.000001	#	Query	#	#	use `test`; create table t1 (a int) engine=innodb
+mysqld-bin.000001	#	Query	#	#	BEGIN
+mysqld-bin.000001	#	Query	#	#	use `test`; insert t1 values (1)
+mysqld-bin.000001	#	Query	#	#	use `test`; insert t1 values (2)
+mysqld-bin.000001	#	Query	#	#	COMMIT
+drop table t1;
 uninstall plugin innodb;

mysql-test/t/innodb_load_xa.test

@@ -8,4 +8,11 @@ if (!$HA_INNODB_SO) {
 }
 install plugin innodb soname 'ha_innodb';
 select engine,support,transactions,xa from information_schema.engines where engine='innodb';
+create table t1 (a int) engine=innodb;
+start transaction;
+insert t1 values (1);
+insert t1 values (2);
+commit;
+--source include/show_binlog_events.inc
+drop table t1;
 uninstall plugin innodb;

storage/innobase/handler/ha_innodb.cc

@@ -2658,6 +2658,14 @@ innobase_end(
 
 	if (innodb_inited) {
 
+		THD *thd= current_thd;
+		if (thd) { // may be UNINSTALL PLUGIN statement
+		 	trx_t* trx = thd_to_trx(thd);
+		 	if (trx) {
+		 		trx_free_for_mysql(trx);
+		 	}
+		}
+
 		srv_fast_shutdown = (ulint) innobase_fast_shutdown;
 		innodb_inited = 0;
 		hash_table_free(innobase_open_tables);

storage/xtradb/handler/ha_innodb.cc

@@ -3276,6 +3276,14 @@ innobase_end(
 
 	if (innodb_inited) {
 
+		THD *thd= current_thd;
+		if (thd) { // may be UNINSTALL PLUGIN statement
+		 	trx_t* trx = thd_to_trx(thd);
+		 	if (trx) {
+		 		trx_free_for_mysql(trx);
+		 	}
+		}
+
 		srv_fast_shutdown = (ulint) innobase_fast_shutdown;
 		innodb_inited = 0;
 		hash_table_free(innobase_open_tables);