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Merge mysql.com:/home/mydev/mysql-5.0-bug19815

Browse Source 
into  mysql.com:/home/mydev/mysql-5.1-bug19815
This commit is contained in:
ingo@mysql.com
2006-05-29 15:30:13 +02:00
parent eddfcc147c d00441e328
commit ed2e475548
3 changed files with 89 additions and 14 deletions
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8
mysql-test/r/lock_multi.result
View File

@ -50,3 +50,11 @@ Field Type Null Key Default Extra
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

35
mysql-test/t/lock_multi.test
View File

@ -126,3 +126,38 @@ 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;

60
sql/sql_db.cc
View File

@ -538,16 +538,27 @@ bool mysql_create_db(THD *thd, char *db, HA_CREATE_INFO *create_info,
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 @@ bool mysql_create_db(THD *thd, char *db, HA_CREATE_INFO *create_info,
}
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 @@ bool mysql_alter_db(THD *thd, const char *db, HA_CREATE_INFO *create_info)
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 @@ bool mysql_alter_db(THD *thd, const char *db, HA_CREATE_INFO *create_info)
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 @@ bool mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
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 @@ bool mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
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 @@ exit:
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);
}