connect cancel_purge,localhost,root,,; START TRANSACTION WITH CONSISTENT SNAPSHOT; connection default; CREATE TABLE t (a int PRIMARY KEY, b int) engine = InnoDB; CREATE TABLE t2 (a int PRIMARY KEY) engine = InnoDB; INSERT INTO t VALUES (10, 10), (20, 20), (30, 30); INSERT INTO t2 VALUES (10), (20), (30); BEGIN; SELECT * FROM t WHERE a = 20 FOR UPDATE; a b 20 20 connect con_2,localhost,root,,; SET TRANSACTION ISOLATION LEVEL READ COMMITTED; BEGIN; SET DEBUG_SYNC = 'lock_trx_handle_wait_enter SIGNAL upd_locked WAIT_FOR upd_cont EXECUTE 2'; UPDATE t SET b = 100; connect con_3,localhost,root,,; BEGIN; UPDATE t2 SET a = a + 100; SELECT * FROM t WHERE a = 30 FOR UPDATE; a b 30 30 SET DEBUG_SYNC='now WAIT_FOR upd_locked'; SET DEBUG_SYNC = 'lock_wait_start SIGNAL sel_locked'; SELECT * FROM t WHERE a = 20 FOR UPDATE; connection default; SET DEBUG_SYNC='now WAIT_FOR sel_locked'; ROLLBACK; SET DEBUG_SYNC='now SIGNAL upd_cont'; SET DEBUG_SYNC="now WAIT_FOR upd_locked"; SET SESSION innodb_lock_wait_timeout=1; SELECT * FROM t WHERE a = 10 FOR UPDATE; ERROR HY000: Lock wait timeout exceeded; try restarting transaction SET DEBUG_SYNC="now SIGNAL upd_cont"; connection con_3; a b 20 20 connection con_2; ERROR 40001: Deadlock found when trying to get lock; try restarting transaction disconnect con_3; disconnect con_2; connection default; SET DEBUG_SYNC = 'RESET'; DROP TABLE t; DROP TABLE t2; disconnect cancel_purge;