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, 33 insertions, 0 deletions

diff --git a/mysql-test/t/drop.test b/mysql-test/t/drop.test
index 6be4ea25007..4aeb7165bcb 100644
--- a/mysql-test/t/drop.test
+++ b/mysql-test/t/drop.test
@@ -124,6 +124,39 @@ disconnect addconroot1;
 --source include/wait_until_disconnected.inc
 connection default;
 
+#
+# Bug#25858 Some DROP TABLE under LOCK TABLES can cause deadlocks
+#
+
+--disable_warnings
+drop table if exists t1,t2;
+--enable_warnings
+create table t1 (a int);
+create table t2 (a int);
+lock table t1 read;
+--error ER_TABLE_NOT_LOCKED
+drop table t2;
+--error ER_TABLE_NOT_LOCKED_FOR_WRITE
+drop table t1;
+unlock tables;
+drop table t1,t2;
+connect (addconroot, localhost, root,,);
+connection default;
+create table t1 (i int);
+create table t2 (i int);
+lock tables t1 read;
+connection addconroot;
+lock tables t2 read;
+--error ER_TABLE_NOT_LOCKED
+drop table t1;
+connection default;
+--error ER_TABLE_NOT_LOCKED_FOR_WRITE
+drop table t1,t2;
+disconnect addconroot;
+connection default;
+unlock tables;
+drop table t1,t2;
+
 --echo End of 5.0 tests
 
 #