From 4f8407b6315736ab52b49e1e248e7585614c3f20 Mon Sep 17 00:00:00 2001 From: unknown Date: Mon, 29 May 2006 15:26:23 +0200 Subject: Bug#19815 - CREATE/RENAME/DROP DATABASE can deadlock on a global read lock 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. mysql-test/r/lock_multi.result: Bug#19815 - CREATE/RENAME/DROP DATABASE can deadlock on a global read lock The test result mysql-test/t/lock_multi.test: Bug#19815 - CREATE/RENAME/DROP DATABASE can deadlock on a global read lock The test case sql/sql_db.cc: Bug#19815 - CREATE/RENAME/DROP DATABASE can deadlock on a global read lock Exchanged the order of acquiring LOCK_mysql_create_db and wait_if_global_read_lock(). --- mysql-test/t/lock_multi.test | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) (limited to 'mysql-test/t/lock_multi.test') diff --git a/mysql-test/t/lock_multi.test b/mysql-test/t/lock_multi.test index 0d2266fc2ae..c7d2bcdfbc5 100644 --- a/mysql-test/t/lock_multi.test +++ b/mysql-test/t/lock_multi.test @@ -107,3 +107,38 @@ show columns from t1; connection locker; unlock tables; drop table t1; + +# +# Bug#19815 - CREATE/RENAME/DROP DATABASE can deadlock on a global read lock +# +connect (con1,localhost,root,,); +connect (con2,localhost,root,,); +# +connection con1; +CREATE DATABASE mysqltest_1; +FLUSH TABLES WITH READ LOCK; +# +# With bug in place: acquire LOCK_mysql_create_table and +# wait in wait_if_global_read_lock(). +connection con2; +send DROP DATABASE mysqltest_1; +--sleep 1 +# +# With bug in place: try to acquire LOCK_mysql_create_table... +# When fixed: Reject dropping db because of the read lock. +connection con1; +--error ER_CANT_UPDATE_WITH_READLOCK +DROP DATABASE mysqltest_1; +UNLOCK TABLES; +# +connection con2; +reap; +# +connection default; +disconnect con1; +disconnect con2; +# This must have been dropped by connection 2 already, +# which waited until the global read lock was released. +--error ER_DB_DROP_EXISTS +DROP DATABASE mysqltest_1; + -- cgit v1.2.1