MDEV-33172 : Galera test case galera_mdl_race unstable

Add wait_condition between debug sync SIGNAL points and other
expected state conditions and refactor actual sync point for
easier to use in test case.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

mysql-test/suite/galera/r/galera_mdl_race.result

 connection node_2;
 connection node_1;
+connection node_1;
 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY, f2 CHAR(1)) engine=innodb;
 CREATE TABLE t2 (f1 INTEGER PRIMARY KEY, f2 CHAR(1)) engine=innodb;
 INSERT INTO t1 VALUES (1, 'a');
 INSERT INTO t1 VALUES (2, 'a');
-connection node_1;
 SET AUTOCOMMIT=ON;
 START TRANSACTION;
 UPDATE t1 SET f2 = 'b' WHERE f1 = 1;
 connect node_1a, 127.0.0.1, root, , test, $NODE_MYPORT_1;
 connection node_1a;
+SET SESSION wsrep_sync_wait=0;
 LOCK TABLE t2 WRITE;
 connection node_1;
-SET @@debug_dbug = "d,sync.wsrep_before_mdl_wait";
+SET DEBUG_SYNC= 'wsrep_before_mdl_wait SIGNAL before_mdl_wait WAIT_FOR mdl_wait_continue';
 SELECT * FROM t2;;
 connection node_1a;
+# Wait until select is blocked before MDL lock wait
+SET DEBUG_SYNC= 'now WAIT_FOR before_mdl_wait';
+connection node_1a;
 SET @@debug_dbug = "d,sync.wsrep_after_BF_victim_lock";
 connection node_2;
 UPDATE t1 SET f2 = 'c' WHERE f1 = 1;
-connection node_1a;
-SET @@debug_dbug = "";
-SET DEBUG_SYNC = "now SIGNAL signal.wsrep_before_mdl_wait";
+connect node_1b, 127.0.0.1, root, , test, $NODE_MYPORT_1;
+connection node_1b;
+SET SESSION wsrep_sync_wait=0;
+# Wait for conflicting update to block
 SET DEBUG_SYNC = "now SIGNAL signal.wsrep_after_BF_victim_lock";
+connect node_1c, 127.0.0.1, root, , test, $NODE_MYPORT_1;
+connection node_1c;
+connection node_1a;
+SET DEBUG_SYNC = "now SIGNAL BF_victim_continue";
 UNLOCK TABLES;
 connection node_1;
 ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'a';
-COUNT(*) = 1
+connection node_1;
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'a';
+EXPECT_1
 1
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'c';
-COUNT(*) = 1
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'c';
+EXPECT_1
 1
+SELECT * FROM t1;
+f1	f2
+1	c
+2	a
 connection node_2;
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'a';
-COUNT(*) = 1
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'a';
+EXPECT_1
 1
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'c';
-COUNT(*) = 1
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'c';
+EXPECT_1
 1
+SELECT * FROM t1;
+f1	f2
+1	c
+2	a
 DROP TABLE t1;
 DROP TABLE t2;
 connection node_1a;
 SET DEBUG_SYNC = "RESET";
+connection node_1b;
+SET DEBUG_SYNC = "RESET";
+connection node_1;
+disconnect node_1a;
+disconnect node_1b;
+disconnect node_1c;

mysql-test/suite/galera/t/galera_mdl_race.test

@@ -3,70 +3,92 @@
 #
 
 --source include/galera_cluster.inc
+--source include/have_debug.inc
 --source include/have_debug_sync.inc
 
+--connection node_1
 CREATE TABLE t1 (f1 INTEGER PRIMARY KEY, f2 CHAR(1)) engine=innodb;
 CREATE TABLE t2 (f1 INTEGER PRIMARY KEY, f2 CHAR(1)) engine=innodb;
 INSERT INTO t1 VALUES (1, 'a');
 INSERT INTO t1 VALUES (2, 'a');
 
---connection node_1
 SET AUTOCOMMIT=ON;
 START TRANSACTION;
-
 UPDATE t1 SET f2 = 'b' WHERE f1 = 1;
 
 # block access to t2
 --connect node_1a, 127.0.0.1, root, , test, $NODE_MYPORT_1
 --connection node_1a
+SET SESSION wsrep_sync_wait=0;
+--let $wait_condition = SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't2'
+--let $wait_condition_on_error_output = SELECT * FROM INFORMATION_SCHEMA.TABLES
+--source include/wait_condition_with_debug.inc
 LOCK TABLE t2 WRITE;
 
-# Block before MLD lock wait
+# Block before MDL lock wait
 --connection node_1
-  SET @@debug_dbug = "d,sync.wsrep_before_mdl_wait";
+SET DEBUG_SYNC= 'wsrep_before_mdl_wait SIGNAL before_mdl_wait WAIT_FOR mdl_wait_continue';
 --send SELECT * FROM t2;
 
-# Wait for SELECT to be blocked
 --connection node_1a
-#--let $wait_condition = SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIS  WHERE STATE = 'System lock';
-#--source include/wait_condition.inc
-#--let $wait_condition = SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST WHERE STATE = 'init' AND INFO = 'COMMIT';
-#--source include/wait_condition.inc
+--echo # Wait until select is blocked before MDL lock wait
+SET DEBUG_SYNC= 'now WAIT_FOR before_mdl_wait';
 
 # block applier to wait after BF victim is locked
+--connection node_1a
 SET @@debug_dbug = "d,sync.wsrep_after_BF_victim_lock";
 
 # Issue a conflicting update on node #2
 --connection node_2
 UPDATE t1 SET f2 = 'c' WHERE f1 = 1;
 
+--connect node_1b, 127.0.0.1, root, , test, $NODE_MYPORT_1
+--connection node_1b
+SET SESSION wsrep_sync_wait=0;
+--echo # Wait for conflicting update to block
+--let $wait_condition = SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.PROCESSLIST  WHERE STATE LIKE 'Update_rows_log_event:%';
+--source include/wait_condition.inc
+
 # Unblock the SELECT, to enter wsrep_thd_is_BF
---connection node_1a
-SET @@debug_dbug = "";
-SET DEBUG_SYNC = "now SIGNAL signal.wsrep_before_mdl_wait";
+SET DEBUG_SYNC = "now SIGNAL signal.wsrep_after_BF_victim_lock";
+
+--connect node_1c, 127.0.0.1, root, , test, $NODE_MYPORT_1
+--connection node_1c
+--let $wait_condition = SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.PROCESSLIST  WHERE STATE LIKE 'Update_rows_log_event:%';
+--source include/wait_condition.inc
 
+--connection node_1a
 # unblock applier to try to BF the SELECT
-SET DEBUG_SYNC = "now SIGNAL signal.wsrep_after_BF_victim_lock";
+SET DEBUG_SYNC = "now SIGNAL BF_victim_continue";
 
 # table lock is not needed anymore
 UNLOCK TABLES;
 
-# SELECT succeeds
+# SELECT returns deadlock
 --connection node_1
-
 --error ER_LOCK_DEADLOCK
 --reap
 
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'a';
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'c';
+--connection node_1
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'a';
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'c';
+SELECT * FROM t1;
 
 --connection node_2
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'a';
-SELECT COUNT(*) = 1 FROM t1 WHERE f2 = 'c';
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'a';
+SELECT COUNT(*) AS EXPECT_1 FROM t1 WHERE f2 = 'c';
+SELECT * FROM t1;
 
 DROP TABLE t1;
 DROP TABLE t2;
 
 --connection node_1a
 SET DEBUG_SYNC = "RESET";
+--connection node_1b
+SET DEBUG_SYNC = "RESET";
+
+--connection node_1
+--disconnect node_1a
+--disconnect node_1b
+--disconnect node_1c
 

sql/mdl.cc

@@ -1176,15 +1176,8 @@ MDL_wait::timed_wait(MDL_context_owner *owner, struct timespec *abs_timeout,
   {
 #ifdef WITH_WSREP
 # ifdef ENABLED_DEBUG_SYNC
-    // Allow tests to block the applier thread using the DBUG facilities
-    DBUG_EXECUTE_IF("sync.wsrep_before_mdl_wait",
-                 {
-                   const char act[]=
-                     "now "
-                     "wait_for signal.wsrep_before_mdl_wait";
-                   DBUG_ASSERT(!debug_sync_set_action((owner->get_thd()),
-                                                      STRING_WITH_LEN(act)));
-                 };);
+    // Allow tests to block thread before MDL-wait
+    DEBUG_SYNC(owner->get_thd(), "wsrep_before_mdl_wait");
 # endif
     if (WSREP_ON && wsrep_thd_is_BF(owner->get_thd(), false))
     {