From 1b34d593b5f981b523fdc8e923e2c2eb0da75a31 Mon Sep 17 00:00:00 2001 From: Konstantin Osipov Date: Fri, 20 Nov 2009 22:51:12 +0300 Subject: 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. --- mysql-test/r/lock_multi.result | 1 + 1 file changed, 1 insertion(+) (limited to 'mysql-test/r/lock_multi.result') diff --git a/mysql-test/r/lock_multi.result b/mysql-test/r/lock_multi.result index d8768e802ea..49e51631b91 100644 --- a/mysql-test/r/lock_multi.result +++ b/mysql-test/r/lock_multi.result @@ -27,6 +27,7 @@ update t1,t2 set c=a where b=d; select c from t2; c 2 +unlock tables; drop table t1; drop table t2; create table t1 (a int); -- cgit v1.2.1