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mariadb/mysql-test/t/flush.test
Dmitry Lenev 378cdc58c1 Patch that refactors global read lock implementation and fixes 
bug #57006 "Deadlock between HANDLER and FLUSH TABLES WITH READ
LOCK" and bug #54673 "It takes too long to get readlock for
'FLUSH TABLES WITH READ LOCK'".

The first bug manifested itself as a deadlock which occurred
when a connection, which had some table open through HANDLER
statement, tried to update some data through DML statement
while another connection tried to execute FLUSH TABLES WITH
READ LOCK concurrently.

What happened was that FTWRL in the second connection managed
to perform first step of GRL acquisition and thus blocked all
upcoming DML. After that it started to wait for table open
through HANDLER statement to be flushed. When the first connection
tried to execute DML it has started to wait for GRL/the second
connection creating deadlock.

The second bug manifested itself as starvation of FLUSH TABLES
WITH READ LOCK statements in cases when there was a constant
stream of concurrent DML statements (in two or more
connections).

This has happened because requests for protection against GRL
which were acquired by DML statements were ignoring presence of
pending GRL and thus the latter was starved.

This patch solves both these problems by re-implementing GRL
using metadata locks.

Similar to the old implementation acquisition of GRL in new
implementation is two-step. During the first step we block
all concurrent DML and DDL statements by acquiring global S
metadata lock (each DML and DDL statement acquires global IX
lock for its duration). During the second step we block commits
by acquiring global S lock in COMMIT namespace (commit code
acquires global IX lock in this namespace).

Note that unlike in old implementation acquisition of
protection against GRL in DML and DDL is semi-automatic.
We assume that any statement which should be blocked by GRL
will either open and acquires write-lock on tables or acquires
metadata locks on objects it is going to modify. For any such
statement global IX metadata lock is automatically acquired
for its duration.

The first problem is solved because waits for GRL become
visible to deadlock detector in metadata locking subsystem
and thus deadlocks like one in the first bug become impossible.

The second problem is solved because global S locks which
are used for GRL implementation are given preference over
IX locks which are acquired by concurrent DML (and we can
switch to fair scheduling in future if needed).

Important change:
FTWRL/GRL no longer blocks DML and DDL on temporary tables.
Before this patch behavior was not consistent in this respect:
in some cases DML/DDL statements on temporary tables were
blocked while in others they were not. Since the main use cases
for FTWRL are various forms of backups and temporary tables are
not preserved during backups we have opted for consistently
allowing DML/DDL on temporary tables during FTWRL/GRL.

Important change:
This patch changes thread state names which are used when
DML/DDL of FTWRL is waiting for global read lock. It is now
either "Waiting for global read lock" or "Waiting for commit
lock" depending on the stage on which FTWRL is.

Incompatible change:
To solve deadlock in events code which was exposed by this
patch we have to replace LOCK_event_metadata mutex with
metadata locks on events. As result we have to prohibit
DDL on events under LOCK TABLES.

This patch also adds extensive test coverage for interaction
of DML/DDL and FTWRL.

Performance of new and old global read lock implementations
in sysbench tests were compared. There were no significant
difference between new and old implementations.
2010-11-11 20:11:05 +03:00

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connect (con1,localhost,root,,);
connect (con2,localhost,root,,);
connection con1;
--disable_warnings
drop table if exists t1,t2;
drop database if exists mysqltest;
--enable_warnings
create temporary table t1(n int not null primary key);
create table t2(n int);
insert into t2 values(3);
let $1=100;
disable_query_log;
while ($1)
{
connection con1;
send replace into t1 select n from t2;
connection con2;
send flush tables;
connection con1;
reap;
connection con2;
reap;
dec $1;
}
enable_query_log;
connection con1;
select * from t1;
connection con2;
flush tables with read lock;
--error 1223
drop table t2;
connection con1;
send drop table t2;
connection con2;
unlock tables;
connection con1;
reap;
#test if drop database will wait until we release the global read lock
connection con1;
create database mysqltest;
create table mysqltest.t1(n int);
insert into mysqltest.t1 values (23);
flush tables with read lock;
connection con2;
send drop database mysqltest;
connection con1;
select * from mysqltest.t1;
unlock tables;
connection con2;
reap;
# test if dirty close releases global read lock
connection con1;
create table t1 (n int);
flush tables with read lock;
dirty_close con1;
connection con2;
insert into t1 values (345);
select * from t1;
drop table t1;
#
# Bug#9459 - deadlock with flush with lock, and lock table write
#
create table t1 (c1 int);
lock table t1 write;
# Cannot get the global read lock with write locked tables.
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
lock table t1 read;
# Cannot get the global read lock with read locked tables.
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
unlock tables;
flush tables with read lock;
--error 1223
lock table t1 write;
lock table t1 read;
--error 1223
lock table t1 write;
# Release all table locks and the global read lock.
unlock tables;
create table t2 (c1 int);
create table t3 (c1 int);
lock table t1 read, t2 read, t3 write;
# Cannot get the global read lock with write locked tables.
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
lock table t1 read, t2 read, t3 read;
# Cannot get the global read lock with read locked tables.
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
unlock tables;
drop table t1, t2, t3;
# End of 4.1 tests
#
# Test of deadlock problem when doing FLUSH TABLE with read lock
# (Bug was in NTPL threads in Linux when using different mutex while
# waiting for a condtion variable)
create table t1 (c1 int);
create table t2 (c1 int);
connect (con1,localhost,root,,);
connect (con3,localhost,root,,);
connection con1;
lock table t1 write;
connection con2;
send flush tables with read lock;
--sleep 1
connection con3;
send insert into t2 values(1);
--sleep 1
connection con1;
unlock tables;
disconnect con1;
connection con2;
reap;
disconnect con2;
connection con3;
# It hangs here (insert into t2 does not end).
reap;
disconnect con3;
connection default;
drop table t1, t2;
#
# Bug#32528 Global read lock with a low priority write lock causes a server crash
#
--disable_warnings
drop table if exists t1, t2;
--enable_warnings
set session low_priority_updates=1;
create table t1 (a int);
create table t2 (b int);
lock tables t1 write;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
unlock tables;
lock tables t1 read, t2 write;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
unlock tables;
lock tables t1 read;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
unlock tables;
drop table t1, t2;
set session low_priority_updates=default;
#
# Bug #33334 mysqltest_embedded crashes when disconnecting before reap
#
connect (con1,localhost,root,,);
send select benchmark(200, (select sin(1))) > 1000;
disconnect con1;
--source include/wait_until_disconnected.inc
connection default;
--echo End of 5.0 tests
#
# Bug #26380: LOCK TABLES + FLUSH LOGS causes deadlock
#
set @old_general_log= @@general_log;
set @old_read_only= @@read_only;
set global general_log= on;
flush tables with read lock;
flush logs;
unlock tables;
set global read_only=1;
flush logs;
unlock tables;
flush tables with read lock;
flush logs;
unlock tables;
set global general_log= @old_general_log;
set global read_only= @old_read_only;
--echo End of 5.1 tests
--echo #
--echo # Additional test for bug #51136 "Crash in pthread_rwlock_rdlock
--echo # on TEMPORARY + HANDLER + LOCK + SP".
--echo # Also see the main test for this bug in include/handler.inc.
--echo #
--disable_warnings
drop tables if exists t1, t2;
--enable_warnings
create table t1 (i int);
create temporary table t2 (j int);
flush tables with read lock;
lock table t2 read;
--echo # This commit should not release any MDL locks.
commit;
--echo # The below statement crashed before the bug fix as it
--echo # has attempted to release global shared metadata lock
--echo # which was already released by commit.
unlock tables;
drop tables t1, t2;
--echo #
--echo # Tests for WL#5000 FLUSH TABLES|TABLE table_list WITH READ LOCK
--echo #
--echo # I. Check the incompatible changes in the grammar.
--echo #
--error ER_PARSE_ERROR
flush tables with read lock, hosts;
--error ER_PARSE_ERROR
flush privileges, tables;
--error ER_PARSE_ERROR
flush privileges, tables with read lock;
--error ER_PARSE_ERROR
flush privileges, tables;
--error ER_PARSE_ERROR
flush tables with read lock, tables;
show tables;
--echo #
--echo # II. Check the allowed syntax.
--echo #
--disable_warnings
drop table if exists t1, t2, t3;
--enable_warnings
create table t1 (a int);
create table t2 (a int);
create table t3 (a int);
lock table t1 read, t2 read;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
unlock tables;
flush tables with read lock;
flush tables t1, t2 with read lock;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables t1, t2 with read lock;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
flush tables with read lock;
select * from t1;
select * from t2;
--error ER_TABLE_NOT_LOCKED
select * from t3;
--error ER_TABLE_NOT_LOCKED_FOR_WRITE
insert into t1 (a) values (1);
--error ER_TABLE_NOT_LOCKED_FOR_WRITE
insert into t2 (a) values (1);
--error ER_TABLE_NOT_LOCKED
insert into t3 (a) values (1);
--error ER_NO_SUCH_TABLE
lock table no_such_table read;
--echo #
--echo # We implicitly left the locked tables
--echo # mode but still have the read lock.
--echo #
--error ER_CANT_UPDATE_WITH_READLOCK
insert into t2 (a) values (1);
unlock tables;
insert into t1 (a) values (1);
insert into t2 (a) values (1);
flush table t1, t2 with read lock;
select * from t1;
select * from t2;
--error ER_TABLE_NOT_LOCKED
select * from t3;
--error ER_TABLE_NOT_LOCKED_FOR_WRITE
insert into t1 (a) values (2);
--error ER_TABLE_NOT_LOCKED_FOR_WRITE
insert into t2 (a) values (2);
--error ER_TABLE_NOT_LOCKED
insert into t3 (a) values (2);
--error ER_NO_SUCH_TABLE
lock table no_such_table read;
insert into t3 (a) values (2);
--echo #
--echo # III. Concurrent tests.
--echo #
connect (con1,localhost,root,,);
--echo # --> connection default
--echo #
--echo # Check that flush tables <list> with read lock
--echo # does not affect non-locked tables.
connection default;
--echo #
flush tables t1 with read lock;
--echo # --> connection con1;
connection con1;
select * from t1;
select * from t2;
insert into t2 (a) values (3);
--echo # --> connection default;
connection default;
unlock tables;
--echo #
--echo # Check that "FLUSH TABLES <list> WITH READ LOCK" is
--echo # compatible with active "FLUSH TABLES WITH READ LOCK".
--echo # Vice versa it is not true, since tables read-locked by
--echo # "FLUSH TABLES <list> WITH READ LOCK" can't be flushed.
flush tables with read lock;
--echo # --> connection con1;
connection con1;
flush table t1 with read lock;
select * from t1;
unlock tables;
--echo # --> connection default;
connection default;
unlock tables;
--echo #
--echo # Check that FLUSH TABLES t1 WITH READ LOCK
--echo # does not conflict with an existing FLUSH TABLES t2
--echo # WITH READ LOCK.
--echo #
flush table t1 with read lock;
--echo # --> connection con1
connection con1;
flush table t2 with read lock;
unlock tables;
--echo # --> connection default
connection default;
unlock tables;
--echo #
--echo # Check that FLUSH TABLES t1 WITH READ LOCK
--echo # does not conflict with SET GLOBAL read_only=1.
--echo #
set global read_only=1;
--echo # connection con1
connection con1;
flush table t1 with read lock;
unlock tables;
--echo # connection default
connection default;
set global read_only=0;
--echo #
--echo # Check that it's possible to read-lock
--echo # tables locked with FLUSH TABLE <list> WITH READ LOCK.
--echo #
flush tables t1, t2 with read lock;
--echo # connection con1
connection con1;
lock table t1 read, t2 read;
unlock tables;
--echo # connection default
connection default;
unlock tables;
--echo # --> connection con1
connection con1;
disconnect con1;
--source include/wait_until_disconnected.inc
connection default;
drop table t1, t2, t3;
--echo #
--echo # Bug#51710 FLUSH TABLES <view> WITH READ LOCK kills the server
--echo #
--disable_warnings
drop view if exists v1, v2, v3;
drop table if exists t1, v1;
--enable_warnings
create table t1 (a int);
create view v1 as select 1;
create view v2 as select * from t1;
create view v3 as select * from v2;
--error ER_WRONG_OBJECT
flush table v1, v2, v3 with read lock;
--error ER_WRONG_OBJECT
flush table v1 with read lock;
--error ER_WRONG_OBJECT
flush table v2 with read lock;
--error ER_WRONG_OBJECT
flush table v3 with read lock;
create temporary table v1 (a int);
--error ER_WRONG_OBJECT
flush table v1 with read lock;
drop view v1;
create table v1 (a int);
flush table v1 with read lock;
drop temporary table v1;
unlock tables;
drop view v2, v3;
drop table t1, v1;
--echo #
--echo # FLUSH TABLES <list> WITH READ LOCK and HANDLER
--echo #
--disable_warnings
drop table if exists t1;
--enable_warnings
create table t1 (a int, key a (a));
insert into t1 (a) values (1), (2), (3);
handler t1 open;
handler t1 read a next;
handler t1 read a next;
flush tables t1 with read lock;
--error ER_LOCK_OR_ACTIVE_TRANSACTION
handler t1 read a next;
unlock tables;
--echo #
--echo # Sic: lost handler position.
--echo #
handler t1 read a next;
handler t1 close;
drop table t1;
--echo #
--echo # Bug#52117 Pending FLUSH TALBES <list> aborts
--echo # transactions unnecessarily.
--echo #
--disable_warnings
drop table if exists t1;
--enable_warnings
connect (con1,localhost,root,,);
connect (con2,localhost,root,,);
--echo # --> conection default
connection default;
create table t1 (a int);
begin;
select * from t1;
--echo # --> connection con1
connection con1;
--echo #
--echo # Issue a LOCK TABLE t1 READ. We could use HANDLER t1 OPEN
--echo # or a long-running select -- anything that
--echo # prevents FLUSH TABLE t1 from immediate completion would do.
--echo #
lock table t1 read;
--echo # --> connection con2
connection con2;
--echo #
--echo # FLUSH TABLE expels the table definition from the cache.
--echo # Sending 'flush table t1'...
send flush table t1;
--echo # --> connection default
connection default;
--echo # Let flush table sync in.
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for table flush"
and info = "flush table t1";
--source include/wait_condition.inc
send select * from t1;
--echo # --> connection con1
connection con1;
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for table flush"
and info = "select * from t1";
select * from t1;
unlock tables;
--echo # --> connection con2
connection con2;
--echo # Reaping 'flush table t1'...
reap;
--echo # --> connection default
connection default;
--echo # Reaping 'select * from t1'...
reap;
commit;
--echo #
--echo # Repeat the same test but with FLUSH TABLES
--echo #
begin;
select * from t1;
--echo # --> connection con1
connection con1;
--echo #
--echo # Issue a LOCK TABLE t1 READ.
--echo #
lock table t1 read;
--echo # --> connection con2
connection con2;
--echo #
--echo # FLUSH TABLES expels the table definition from the cache.
--echo # Sending 'flush tables'...
send flush tables;
--echo # --> connection default
connection default;
--echo # Let flush table sync in.
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for table flush"
and info = "flush tables";
--source include/wait_condition.inc
send select * from t1;
--echo # --> connection con1
connection con1;
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for table flush"
and info = "select * from t1";
select * from t1;
unlock tables;
--echo # --> connection con2
connection con2;
--echo # Reaping 'flush tables'...
reap;
--echo # --> connection default
connection default;
--echo # Reaping 'select * from t1'...
reap;
commit;
--echo # Cleanup
--echo # --> connection con1
connection con1;
disconnect con1;
--source include/wait_until_disconnected.inc
--echo # --> connection con2
connection con2;
disconnect con2;
--source include/wait_until_disconnected.inc
--echo # --> connection default
connection default;
drop table t1;
--echo #
--echo # Test for bug #55273 "FLUSH TABLE tm WITH READ LOCK for Merge table
--echo # causes assert failure".
--echo #
--disable_warnings
drop table if exists t1, t2, tm;
--enable_warnings
create table t1 (i int);
create table t2 (i int);
create table tm (i int) engine=merge union=(t1, t2);
insert into t1 values (1), (2);
insert into t2 values (3), (4);
--echo # The below statement should succeed and lock merge
--echo # table for read. Only merge table gets flushed and
--echo # not underlying tables.
flush tables tm with read lock;
select * from tm;
--echo # Check that underlying tables are locked.
select * from t1;
select * from t2;
unlock tables;
--echo # This statement should succeed as well and flush
--echo # all tables in the list.
flush tables tm, t1, t2 with read lock;
select * from tm;
--echo # Naturally, underlying tables should be locked in this case too.
select * from t1;
select * from t2;
unlock tables;
drop tables tm, t1, t2;
--echo #
--echo # Test for bug #57006 "Deadlock between HANDLER and
--echo # FLUSH TABLES WITH READ LOCK".
--echo #
--disable_warnings
drop table if exists t1, t2;
--enable_warnings
connect (con1,localhost,root,,);
connect (con2,localhost,root,,);
connection default;
create table t1 (i int);
create table t2 (i int);
handler t1 open;
--echo # Switching to connection 'con1'.
connection con1;
--echo # Sending:
--send flush tables with read lock
--echo # Switching to connection 'con2'.
connection con2;
--echo # Wait until FTWRL starts waiting for 't1' to be closed.
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for table flush"
and info = "flush tables with read lock";
--source include/wait_condition.inc
--echo # Switching to connection 'default'.
connection default;
--echo # The below statement should not cause deadlock.
--echo # Sending:
--send insert into t2 values (1)
--echo # Switching to connection 'con2'.
connection con2;
--echo # Wait until INSERT starts to wait for FTWRL to go away.
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for global read lock"
and info = "insert into t2 values (1)";
--source include/wait_condition.inc
--echo # Switching to connection 'con1'.
connection con1;
--echo # FTWRL should be able to continue now.
--echo # Reap FTWRL.
--reap
unlock tables;
--echo # Switching to connection 'default'.
connection default;
--echo # Reap INSERT.
--reap
handler t1 close;
--echo # Cleanup.
connection con1;
disconnect con1;
--source include/wait_until_disconnected.inc
connection con2;
disconnect con2;
--source include/wait_until_disconnected.inc
connection default;
drop tables t1, t2;
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