昨天看到一個很有意思的死鎖，拿來記錄下：

環(huán)境:deadlock on

事務(wù)隔離級別: read commited

表結(jié)構(gòu)：

root@test 08:34:01>show create table lingluo\G *************************** 1. row ***************************Table: lingluo Create Table: CREATE TABLE `lingluo` (`a` int(11) NOT NULL DEFAULT '0',`b` int(11) DEFAULT NULL,`c` int(11) DEFAULT NULL,`d` int(11) DEFAULT NULL,PRIMARY KEY (`a`),UNIQUE KEY `uk_bc` (`b`,`c`) ) ENGINE=InnoDB DEFAULT CHARSET=gbk 1 row in set (0.00 sec)

session 1:

root@test 08:45:51>select * from lingluo; +--------+------+------+------+ | a | b | c | d | +--------+------+------+------+ | 1 | 2 | 3 | 4 | | 500 | 100 | 200 | 43 | | 1000 | 10 | 20 | 43 | | 10001 | 21 | 21 | 32 | | 100202 | 213 | 213 | 312 | | 100212 | 214 | 214 | 312 | +--------+------+------+------+ 6 rows in set (0.00 sec)root@test 08:46:38>begin; Query OK, 0 rows affected (0.00 sec)root@test 08:47:04>insert into lingluo values(100213,215,215,312); Query OK, 1 row affected (0.00 sec)

session 2:

root@test 08:46:02>begin; Query OK, 0 rows affected (0.00 sec)root@test 08:47:20>insert into lingluo values(100214,215,215,312); Query OK, 1 row affected (12.77 sec)

session3:

root@test 08:46:24>begin; Query OK, 0 rows affected (0.00 sec)root@test 08:47:23>insert into lingluo values(100215,215,215,312);

session 1 rollback前:

---TRANSACTION 4F3D6F33, ACTIVE 3 sec inserting mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 376, 1 row lock(s), undo log entries 1 MySQL thread id 18124715, OS thread handle 0x7fea34912700, query id 1435660081 localhost root update insert into lingluo values(100215,215,215,312) ------- TRX HAS BEEN WAITING 3 SEC FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6F33 lock mode S waiting ------------------ TABLE LOCK table `test`.`lingluo` trx id 4F3D6F33 lock mode IX RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6F33 lock mode S waiting ---TRANSACTION 4F3D6D24, ACTIVE 5 sec inserting mysql tables in use 1, locked 1 LOCK WAIT 2 lock struct(s), heap size 376, 1 row lock(s), undo log entries 1 MySQL thread id 18124702, OS thread handle 0x7fe706fdf700, query id 1435659684 localhost root update insert into lingluo values(100214,215,215,312) ------- TRX HAS BEEN WAITING 5 SEC FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock mode S waiting ------------------ TABLE LOCK table `test`.`lingluo` trx id 4F3D6D24 lock mode IX RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock mode S waiting ---TRANSACTION 4F3D4423, ACTIVE 33 sec 2 lock struct(s), heap size 376, 1 row lock(s), undo log entries 1 MySQL thread id 18124692, OS thread handle 0x7fe73c89a700, query id 1435651549 localhost root TABLE LOCK table `test`.`lingluo` trx id 4F3D4423 lock mode IX RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D4423 lock_mode X locks rec but not gap

/****

session 1上的轉(zhuǎn)為顯式鎖：lock_mode X locks rec but not gap

session 2等待的鎖：lock mode S waiting

session 3等待的鎖：lock mode S waiting

***/

session 1 rollback

session 2插入成功

session 3:

ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction

這個時候show engine innodb status:

5 lock struct(s), heap size 1248, 3 row lock(s), undo log entries 1 MySQL thread id 18124702, OS thread handle 0x7fe706fdf700, query id 1435659684 localhost root TABLE LOCK table `test`.`lingluo` trx id 4F3D6D24 lock mode IX RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock mode S RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock mode S RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock_mode X insert intention RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock mode S locks gap before rec

死鎖信息：

------------------------ LATEST DETECTED DEADLOCK ------------------------ 130701 20:47:57 *** (1) TRANSACTION: TRANSACTION 4F3D6D24, ACTIVE 13 sec inserting, thread declared inside InnoDB 1 mysql tables in use 1, locked 1 LOCK WAIT 4 lock struct(s), heap size 1248, 2 row lock(s), undo log entries 1 MySQL thread id 18124702, OS thread handle 0x7fe706fdf700, query id 1435659684 localhost root update insert into lingluo values(100214,215,215,312) *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6D24 lock_mode X insert intention waiting *** (2) TRANSACTION: TRANSACTION 4F3D6F33, ACTIVE 11 sec inserting, thread declared inside InnoDB 1 mysql tables in use 1, locked 1 4 lock struct(s), heap size 1248, 2 row lock(s), undo log entries 1 MySQL thread id 18124715, OS thread handle 0x7fea34912700, query id 1435660081 localhost root update insert into lingluo values(100215,215,215,312) *** (2) HOLDS THE LOCK(S): RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6F33 lock mode S *** (2) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 3351 page no 4 n bits 80 index `uk_bc` of table `test`.`lingluo` trx id 4F3D6F33 lock_mode X insert intention waiting *** WE ROLL BACK TRANSACTION (2)

原因:

s1 , type_mode=1059 ? ? //s2為s1轉(zhuǎn)換隱式鎖為顯式鎖

s2, ?type_mode=1282 ? ?//檢查重復(fù)鍵，需要加共享鎖，被s1 block住，等待S鎖

s3, ?type_mode=1282 ? ?// 被s1 block住，等待S鎖

?

s1, type_mode=547 ? ? ? //s1回滾，刪除記錄，lock_update_delete鎖繼承，

s2, type_mode=546 ? ? ? ?//創(chuàng)建s鎖 ?LOCK_GAP | LOCK_REC | LOCK_S

s3, type_mode=546 ? ? ? ?//創(chuàng)建s鎖 ? LOCK_GAP | LOCK_REC | LOCK_S

s2, type_mode=2819 ? // LOCK_X | LOCK_GAP | LOCK_INSERT_INTENTION

s3, type_mode=2819 ? // ?LOCK_X | LOCK_GAP | LOCK_INSERT_INTENTION

當(dāng)s1回滾后，s2和s3獲得s鎖，但隨后s2和s3又先后請求插入意向鎖，因此鎖隊列為：

s2(S GAP)<—s3(S GAP)<—s2(插入意向鎖)<–s3(插入意向鎖) ? s3(s鎖),s2(x鎖),s3(x鎖)形成死鎖。

這樣的死鎖不光出現(xiàn)在unique key，還包括primary key（unique key的特殊形式）

印風(fēng)的博客里有更詳細(xì)的代碼級別的記錄，有興趣的可以看下

另外如果：deadlock off的話,即使session 1rollback了，session 2和session 3還是處于等待的狀態(tài)，除非超過了innodb_lock_wait_timeout的時間，報

ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

這個情況和官方的這篇文章是一樣的http://dev.mysql.com/doc/refman/5.5/en/innodb-locks-set.html?

轉(zhuǎn)載于:https://www.cnblogs.com/sunss/p/3166550.html

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