CREATE TABLE t (a int PRIMARY KEY, b int) engine = InnoDB STATS_PERSISTENT=0; CREATE TABLE t2 (a int PRIMARY KEY) engine = InnoDB STATS_PERSISTENT=0; INSERT INTO t VALUES (10, 10), (20, 20), (30, 30); INSERT INTO t2 VALUES (10), (20), (30); BEGIN; UPDATE t2 SET a = a + 100; SELECT * FROM t WHERE a = 20 FOR UPDATE; a b 20 20 connect con_2,localhost,root,,; SET TRANSACTION ISOLATION LEVEL READ COMMITTED; SET DEBUG_SYNC = 'lock_trx_handle_wait_enter SIGNAL upd_locked WAIT_FOR upd_cont'; SET DEBUG_SYNC = 'trx_t_release_locks_enter SIGNAL sel_cont WAIT_FOR upd_cont_2'; BEGIN; UPDATE t SET b = 100; connection default; SET DEBUG_SYNC="now WAIT_FOR upd_locked"; SET DEBUG_SYNC="deadlock_report_before_lock_releasing SIGNAL upd_cont WAIT_FOR sel_cont"; SET DEBUG_SYNC="lock_wait_before_suspend SIGNAL sel_before_suspend"; SELECT * FROM t WHERE a = 10 FOR UPDATE;; connect con_3,localhost,root,,; SET DEBUG_SYNC="now WAIT_FOR sel_before_suspend"; SET DEBUG_SYNC="now SIGNAL upd_cont_2"; disconnect con_3; connection con_2; ERROR 40001: Deadlock found when trying to get lock; try restarting transaction disconnect con_2; connection default; a b 10 10 SET DEBUG_SYNC = 'RESET'; DROP TABLE t; DROP TABLE t2;