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Backport into build-200906240007-5.1.34sp1

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> ------------------------------------------------------------
> revno: 2852.2.3
> revision-id: davi.arnaut@sun.com-20090403194600-60ufn0tz1gx1kl0l
> parent: gni@mysql.com-20090403184200-vnjtpsv4an79w8bu
> parent: davi.arnaut@sun.com-20090403191154-0ho2nai3chjsmpof
> committer: Davi Arnaut <Davi.Arnaut@Sun.COM>
> branch nick: 43230-5.1
> timestamp: Fri 2009-04-03 16:46:00 -0300
> message:
>   Merge Bug#43230 into mysql-5.1-bugteam
>     ------------------------------------------------------------
>     revno: 1810.3855.16
>     revision-id: davi.arnaut@sun.com-20090403191154-0ho2nai3chjsmpof
>     parent: chad@mysql.com-20090402152928-3ld60a56h86njcpg
>     committer: Davi Arnaut <Davi.Arnaut@Sun.COM>
>     branch nick: 43230-5.0
>     timestamp: Fri 2009-04-03 16:11:54 -0300
>     message:
>       Bug#43230: SELECT ... FOR UPDATE can hang with FLUSH TABLES WITH READ LOCK indefinitely
>       
>       The problem is that a SELECT .. FOR UPDATE statement might open
>       a table and later wait for a impeding global read lock without
>       noticing whether it is holding a table that is being waited upon
>       the the flush phase of the process that took the global read
>       lock.
>       
>       The same problem also affected the following statements:
>       
>       LOCK TABLES .. WRITE
>       UPDATE .. SET (update and multi-table update)
>       TRUNCATE TABLE ..
>       LOAD DATA ..
>       
>       The solution is to make the above statements wait for a impending
>       global read lock before opening the tables. If there is no
>       impending global read lock, the statement raises a temporary
>       protection against global read locks and progresses smoothly
>       towards completion.
>       
>       Important notice: the patch does not try to address all possible
>       cases, only those which are common and can be fixed unintrusively
>       enough for 5.0.
This commit is contained in:
MySQL Build Team 2009-06-24 19:17:12 +02:00
parent 0837b5913d
commit fab67c98ae
6 changed files with 236 additions and 4 deletions
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55
mysql-test/r/lock_multi.result
View file

@ -96,6 +96,61 @@ alter table t1 auto_increment=0;
alter table t1 auto_increment=0;
unlock tables;
drop table t1;
create table t1 (a int);
create table t2 like t1;
# con1
lock tables t1 write;
# con2
flush tables with read lock;
# con5
# global read lock is taken
# con3
select * from t2 for update;
# waiting for release of read lock
# con4
# would hang and later cause a deadlock
flush tables t2;
# clean up
unlock tables;
unlock tables;
a
drop table t1,t2;
#
# Lightweight version:
# Ensure that the wait for a GRL is done before opening tables.
#
create table t1 (a int);
create table t2 like t1;
#
# UPDATE
#
# default
flush tables with read lock;
# con1
update t2 set a = 1;
# default
# statement is waiting for release of read lock
# con2
flush table t2;
# default
unlock tables;
# con1
#
# LOCK TABLES .. WRITE
#
# default
flush tables with read lock;
# con1
lock tables t2 write;
# default
# statement is waiting for release of read lock
# con2
flush table t2;
# default
unlock tables;
# con1
unlock tables;
drop table t1,t2;
End of 5.0 tests
create table t1 (i int);
lock table t1 read;

128
mysql-test/t/lock_multi.test
View file

@ -317,6 +317,134 @@ reap;
connection locker;
drop table t1;
#
# Bug#43230: SELECT ... FOR UPDATE can hang with FLUSH TABLES WITH READ LOCK indefinitely
#
connect (con1,localhost,root,,);
connect (con2,localhost,root,,);
connect (con3,localhost,root,,);
connect (con4,localhost,root,,);
connect (con5,localhost,root,,);
create table t1 (a int);
create table t2 like t1;
connection con1;
--echo # con1
lock tables t1 write;
connection con2;
--echo # con2
send flush tables with read lock;
connection con5;
--echo # con5
let $show_statement= SHOW PROCESSLIST;
let $field= State;
let $condition= = 'Flushing tables';
--source include/wait_show_condition.inc
--echo # global read lock is taken
connection con3;
--echo # con3
send select * from t2 for update;
connection con5;
let $show_statement= SHOW PROCESSLIST;
let $field= State;
let $condition= = 'Waiting for release of readlock';
--source include/wait_show_condition.inc
--echo # waiting for release of read lock
connection con4;
--echo # con4
--echo # would hang and later cause a deadlock
flush tables t2;
connection con1;
--echo # clean up
unlock tables;
connection con2;
--reap
unlock tables;
connection con3;
--reap
connection default;
disconnect con5;
disconnect con4;
disconnect con3;
disconnect con2;
disconnect con1;
drop table t1,t2;
--echo #
--echo # Lightweight version:
--echo # Ensure that the wait for a GRL is done before opening tables.
--echo #
connect (con1,localhost,root,,);
connect (con2,localhost,root,,);
create table t1 (a int);
create table t2 like t1;
--echo #
--echo # UPDATE
--echo #
connection default;
--echo # default
flush tables with read lock;
connection con1;
--echo # con1
send update t2 set a = 1;
connection default;
--echo # default
let $show_statement= SHOW PROCESSLIST;
let $field= State;
let $condition= = 'Waiting for release of readlock';
--source include/wait_show_condition.inc
--echo # statement is waiting for release of read lock
connection con2;
--echo # con2
flush table t2;
connection default;
--echo # default
unlock tables;
connection con1;
--echo # con1
--reap
--echo #
--echo # LOCK TABLES .. WRITE
--echo #
connection default;
--echo # default
flush tables with read lock;
connection con1;
--echo # con1
send lock tables t2 write;
connection default;
--echo # default
let $show_statement= SHOW PROCESSLIST;
let $field= State;
let $condition= = 'Waiting for release of readlock';
--source include/wait_show_condition.inc
--echo # statement is waiting for release of read lock
connection con2;
--echo # con2
flush table t2;
connection default;
--echo # default
unlock tables;
connection con1;
--echo # con1
--reap
unlock tables;
connection default;
disconnect con2;
disconnect con1;
drop table t1,t2;
--echo End of 5.0 tests

1
sql/sql_lex.cc
View file

@ -348,6 +348,7 @@ void lex_start(THD *thd)
lex->nest_level=0 ;
lex->allow_sum_func= 0;
lex->in_sum_func= NULL;
lex->protect_against_global_read_lock= FALSE;
/*
ok, there must be a better solution for this, long-term
I tried "bzero" in the sql_yacc.yy code, but that for

16
sql/sql_lex.h
View file

@ -1745,6 +1745,22 @@ typedef struct st_lex : public Query_tables_list
bool escape_used;
bool is_lex_started; /* If lex_start() did run. For debugging. */
/*
Special case for SELECT .. FOR UPDATE and LOCK TABLES .. WRITE.
Protect from a impending GRL as otherwise the thread might deadlock
if it starts waiting for the GRL in mysql_lock_tables.
The protection is needed because there is a race between setting
the global read lock and waiting for all open tables to be closed.
The problem is a circular wait where a thread holding "old" open
tables will wait for the global read lock to be released while the
thread holding the global read lock will wait for all "old" open
tables to be closed -- the flush part of flush tables with read
lock.
*/
bool protect_against_global_read_lock;
st_lex();
virtual ~st_lex()

33
sql/sql_parse.cc
View file

@ -2200,8 +2200,15 @@ mysql_execute_command(THD *thd)
res= check_access(thd,
lex->exchange ? SELECT_ACL | FILE_ACL : SELECT_ACL,
any_db, 0, 0, 0, 0);
if (!res)
res= execute_sqlcom_select(thd, all_tables);
if (res)
break;
if (!thd->locked_tables && lex->protect_against_global_read_lock &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
break;
res= execute_sqlcom_select(thd, all_tables);
break;
case SQLCOM_PREPARE:
{
@ -3006,6 +3013,9 @@ end_with_restore_list:
DBUG_ASSERT(first_table == all_tables && first_table != 0);
if (update_precheck(thd, all_tables))
break;
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
goto error;
DBUG_ASSERT(select_lex->offset_limit == 0);
unit->set_limit(select_lex);
res= (up_result= mysql_update(thd, all_tables,
@ -3032,6 +3042,15 @@ end_with_restore_list:
else
res= 0;
/*
Protection might have already been risen if its a fall through
from the SQLCOM_UPDATE case above.
*/
if (!thd->locked_tables &&
lex->sql_command == SQLCOM_UPDATE_MULTI &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
goto error;
res= mysql_multi_update_prepare(thd);
#ifdef HAVE_REPLICATION
@ -3229,7 +3248,8 @@ end_with_restore_list:
ER(ER_LOCK_OR_ACTIVE_TRANSACTION), MYF(0));
goto error;
}
if (!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
goto error;
res= mysql_truncate(thd, first_table, 0);
break;
case SQLCOM_DELETE:
@ -3402,6 +3422,10 @@ end_with_restore_list:
if (check_one_table_access(thd, privilege, all_tables))
goto error;
if (!thd->locked_tables &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
goto error;
res= mysql_load(thd, lex->exchange, first_table, lex->field_list,
lex->update_list, lex->value_list, lex->duplicates,
lex->ignore, (bool) lex->local_file);
@ -3472,6 +3496,9 @@ end_with_restore_list:
if (check_table_access(thd, LOCK_TABLES_ACL | SELECT_ACL, all_tables,
UINT_MAX, FALSE))
goto error;
if (lex->protect_against_global_read_lock &&
!(need_start_waiting= !wait_if_global_read_lock(thd, 0, 1)))
goto error;
thd->in_lock_tables=1;
thd->options|= OPTION_TABLE_LOCK;

7
sql/sql_yacc.yy
View file

@ -6538,6 +6538,7 @@ select_lock_type:
lex->current_select->set_lock_for_tables(TL_WRITE);
lex->current_select->lock_option= TL_WRITE;
lex->safe_to_cache_query=0;
lex->protect_against_global_read_lock= TRUE;
}
| LOCK_SYM IN_SYM SHARE_SYM MODE_SYM
{
@ -12182,8 +12183,12 @@ table_lock_list:
table_lock:
table_ident opt_table_alias lock_option
{
if (!Select->add_table_to_list(YYTHD, $1, $2, 0, (thr_lock_type) $3))
thr_lock_type lock_type= (thr_lock_type) $3;
if (!Select->add_table_to_list(YYTHD, $1, $2, 0, lock_type))
MYSQL_YYABORT;
/* If table is to be write locked, protect from a impending GRL. */
if (lock_type >= TL_WRITE_ALLOW_WRITE)
Lex->protect_against_global_read_lock= TRUE;
}
;