Backport of:

------------------------------------------------------------
revno: 2476.784.3
committer: davi@moksha.local
timestamp: Tue 2007-10-02 21:27:31 -0300
message:
Bug#25858 Some DROP TABLE under LOCK TABLES can cause deadlocks
        
When a client (connection) holds a lock on a table and attempts to
drop (obtain a exclusive lock) on a second table that is already
held by a second client and the second client then attempts to
drop the table that is held by the first client, leads to a
circular wait deadlock. This scenario is very similar to trying to
drop (or rename) a table while holding read locks and are
correctly forbidden.
        
The solution is to allow a drop table operation to continue only
if the table being dropped is write (exclusively) locked, or if
the table is temporary, or if the client is not holding any
locks. Using this scheme prevents the creation of a circular
chain in which each client is waiting for one table that the
next client in the chain is holding.
            
This is incompatible change, as can be seen by number of tests
cases that needed to be fixed, but is consistent with respect to
behavior of the different scenarios in which the circular wait
might happen.

mysql-test/r/drop.result:
  Test case result for Bug#25858
mysql-test/r/group_by.result:
  Fix test case result wrt drop table under lock tables -- unlock tables
  before dropping table.
mysql-test/r/insert_notembedded.result:
  Fix test case result wrt drop table under lock tables -- unlock tables
  before dropping table
mysql-test/r/lock.result:
  Fix test case result wrt drop table under lock tables -- unlock tables
  before dropping table.
mysql-test/r/lock_multi.result:
  Fix test case result wrt drop table under lock tables -- unlock tables
  before dropping table.
mysql-test/r/myisam.result:
  Fix test case result wrt drop table under lock tables -- unlock tables
  before dropping table.
mysql-test/r/view.result:
  Fix test case result wrt drop table under lock tables -- unlock tables
  before dropping table.
mysql-test/t/drop.test:
  Add test case for Bug#25858
mysql-test/t/group_by.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
mysql-test/t/insert_notembedded.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
mysql-test/t/lock.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
mysql-test/t/lock_multi.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
mysql-test/t/myisam.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
mysql-test/t/query_cache_notembedded.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
mysql-test/t/view.test:
  Fix test case: unlock tables in preparation for a drop table. In some
  circumstances, dropping tables while holding locks leads to a deadlock.
sql/lock.cc:
  When trying to obtain a name lock under lock tables, ensure that the table is properly exclusively locked and fail otherwise.

1 files changed, 2 insertions, 0 deletions

diff --git a/mysql-test/r/myisam.result b/mysql-test/r/myisam.result
index 95fdc4fb93d..16e8a8e5ad1 100644
--- a/mysql-test/r/myisam.result
+++ b/mysql-test/r/myisam.result
@@ -529,6 +529,7 @@ select straight_join * from t1,t2 force index (primary) where t1.a=t2.a;
 a	a	b
 1	1	1
 2	2	1
+unlock tables;
 drop table t1,t2;
 CREATE TABLE t1 (c1 varchar(250) NOT NULL);
 CREATE TABLE t2 (c1 varchar(250) NOT NULL, PRIMARY KEY (c1));
@@ -542,6 +543,7 @@ INSERT INTO t2 VALUES ('test000001'), ('test000005');
 SELECT t1.c1 AS t1c1, t2.c1 AS t2c1 FROM t1, t2
 WHERE t1.c1 = t2.c1 HAVING t1c1 != t2c1;
 t1c1	t2c1
+UNLOCK TABLES;
 DROP TABLE t1,t2;
 CREATE TABLE t1 (`a` int(11) NOT NULL default '0', `b` int(11) NOT NULL default '0', UNIQUE KEY `a` USING RTREE (`a`,`b`)) ENGINE=MyISAM;
 Got one of the listed errors