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Bug#19815 - CREATE/RENAME/DROP DATABASE can deadlock on a global read lock

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The order of acquiring LOCK_mysql_create_db
and wait_if_global_read_lock() was wrong. It could happen
that a thread held LOCK_mysql_create_db while waiting for
the global read lock to be released. The thread with the
global read lock could try to administrate a database too.
It would first try to lock LOCK_mysql_create_db and hang...

The check if the current thread has the global read lock
is done in wait_if_global_read_lock(), which could not be
reached because of the hang in LOCK_mysql_create_db.

Now I exchanged the order of acquiring LOCK_mysql_create_db
and wait_if_global_read_lock(). This makes 
wait_if_global_read_lock() fail with an error message for
the thread with the global read lock. No deadlock happens.
This commit is contained in:
ingo@mysql.com
2006-05-29 15:26:23 +02:00
parent da1fdb8a5f
commit d00441e328
3 changed files with 89 additions and 14 deletions
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8
mysql-test/r/lock_multi.result
View File

@@ -43,3 +43,11 @@ Field Type Null Key Default Extra
a int(11) YES NULL
unlock tables;
drop table t1;
CREATE DATABASE mysqltest_1;
FLUSH TABLES WITH READ LOCK;
DROP DATABASE mysqltest_1;
DROP DATABASE mysqltest_1;
ERROR HY000: Can't execute the query because you have a conflicting read lock
UNLOCK TABLES;
DROP DATABASE mysqltest_1;
ERROR HY000: Can't drop database 'mysqltest_1'; database doesn't exist