Below is the list of changes that have just been committed into a local
5.1 repository of mydev. When mydev does a push these changes will
be propagated to the main repository and, within 24 hours after the
push, to the public repository.
For information on how to access the public repository
see http://dev.mysql.com/doc/mysql/en/installing-source-tree.html
ChangeSet
1.2393 06/05/29 15:30:13 ingo@stripped +3 -0
Merge mysql.com:/home/mydev/mysql-5.0-bug19815
into mysql.com:/home/mydev/mysql-5.1-bug19815
sql/sql_db.cc
1.134 06/05/29 15:30:08 ingo@stripped +0 -0
SCCS merged
mysql-test/t/lock_multi.test
1.15 06/05/29 15:27:20 ingo@stripped +0 -0
Auto merged
mysql-test/r/lock_multi.result
1.17 06/05/29 15:27:19 ingo@stripped +0 -0
Auto merged
# This is a BitKeeper patch. What follows are the unified diffs for the
# set of deltas contained in the patch. The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User: ingo
# Host: chilla.local
# Root: /home/mydev/mysql-5.1-bug19815/RESYNC
--- 1.133/sql/sql_db.cc 2006-03-02 16:24:57 +01:00
+++ 1.134/sql/sql_db.cc 2006-05-29 15:30:08 +02:00
@@ -538,16 +538,27 @@
my_error(ER_DB_CREATE_EXISTS, MYF(0), db);
DBUG_RETURN(-1);
}
-
- VOID(pthread_mutex_lock(&LOCK_mysql_create_db));
- /* do not create database if another thread is holding read lock */
+ /*
+ Do not create database if another thread is holding read lock.
+ Wait for global read lock before acquiring LOCK_mysql_create_db.
+ After wait_if_global_read_lock() we have protection against another
+ global read lock. If we would acquire LOCK_mysql_create_db first,
+ another thread could step in and get the global read lock before we
+ reach wait_if_global_read_lock(). If this thread tries the same as we
+ (admin a db), it would then go and wait on LOCK_mysql_create_db...
+ Furthermore wait_if_global_read_lock() checks if the current thread
+ has the global read lock and refuses the operation with
+ ER_CANT_UPDATE_WITH_READLOCK if applicable.
+ */
if (wait_if_global_read_lock(thd, 0, 1))
{
error= -1;
goto exit2;
}
+ VOID(pthread_mutex_lock(&LOCK_mysql_create_db));
+
/* Check directory */
path_len= build_table_filename(path, sizeof(path), db, "", "");
path[path_len-1]= 0; // Remove last '/' from path
@@ -655,9 +666,9 @@
}
exit:
+ VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
start_waiting_global_read_lock(thd);
exit2:
- VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
DBUG_RETURN(error);
}
@@ -671,12 +682,23 @@
int error= 0;
DBUG_ENTER("mysql_alter_db");
- VOID(pthread_mutex_lock(&LOCK_mysql_create_db));
-
- /* do not alter database if another thread is holding read lock */
+ /*
+ Do not alter database if another thread is holding read lock.
+ Wait for global read lock before acquiring LOCK_mysql_create_db.
+ After wait_if_global_read_lock() we have protection against another
+ global read lock. If we would acquire LOCK_mysql_create_db first,
+ another thread could step in and get the global read lock before we
+ reach wait_if_global_read_lock(). If this thread tries the same as we
+ (admin a db), it would then go and wait on LOCK_mysql_create_db...
+ Furthermore wait_if_global_read_lock() checks if the current thread
+ has the global read lock and refuses the operation with
+ ER_CANT_UPDATE_WITH_READLOCK if applicable.
+ */
if ((error=wait_if_global_read_lock(thd,0,1)))
goto exit2;
+ VOID(pthread_mutex_lock(&LOCK_mysql_create_db));
+
/*
Recreate db options file: /dbpath/.db.opt
We pass MY_DB_OPT_FILE as "extension" to avoid
@@ -721,9 +743,9 @@
send_ok(thd, result);
exit:
+ VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
start_waiting_global_read_lock(thd);
exit2:
- VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
DBUG_RETURN(error);
}
@@ -755,15 +777,26 @@
TABLE_LIST* dropped_tables= 0;
DBUG_ENTER("mysql_rm_db");
- VOID(pthread_mutex_lock(&LOCK_mysql_create_db));
-
- /* do not drop database if another thread is holding read lock */
+ /*
+ Do not drop database if another thread is holding read lock.
+ Wait for global read lock before acquiring LOCK_mysql_create_db.
+ After wait_if_global_read_lock() we have protection against another
+ global read lock. If we would acquire LOCK_mysql_create_db first,
+ another thread could step in and get the global read lock before we
+ reach wait_if_global_read_lock(). If this thread tries the same as we
+ (admin a db), it would then go and wait on LOCK_mysql_create_db...
+ Furthermore wait_if_global_read_lock() checks if the current thread
+ has the global read lock and refuses the operation with
+ ER_CANT_UPDATE_WITH_READLOCK if applicable.
+ */
if (wait_if_global_read_lock(thd, 0, 1))
{
error= -1;
goto exit2;
}
+ VOID(pthread_mutex_lock(&LOCK_mysql_create_db));
+
length= build_table_filename(path, sizeof(path), db, "", "");
strmov(path+length, MY_DB_OPT_FILE); // Append db option file name
del_dbopt(path); // Remove dboption hash entry
@@ -872,7 +905,6 @@
exit:
(void)sp_drop_db_routines(thd, db); /* QQ Ignore errors for now */
(void)evex_drop_db_events(thd, db); /* QQ Ignore errors for now */
- start_waiting_global_read_lock(thd);
/*
If this database was the client's selected database, we silently change the
client's selected database to nothing (to have an empty SELECT DATABASE()
@@ -901,9 +933,9 @@
thd->db= 0;
thd->db_length= 0;
}
-exit2:
VOID(pthread_mutex_unlock(&LOCK_mysql_create_db));
-
+ start_waiting_global_read_lock(thd);
+exit2:
DBUG_RETURN(error);
}
--- 1.16/mysql-test/r/lock_multi.result 2006-03-29 13:27:30 +02:00
+++ 1.17/mysql-test/r/lock_multi.result 2006-05-29 15:27:19 +02:00
@@ -50,3 +50,11 @@
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
--- 1.14/mysql-test/t/lock_multi.test 2006-03-29 13:27:30 +02:00
+++ 1.15/mysql-test/t/lock_multi.test 2006-05-29 15:27:20 +02:00
@@ -126,3 +126,38 @@
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;
+
| Thread |
|---|
| • bk commit into 5.1 tree (ingo:1.2393) | ingo | 29 May |
