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Patch that changes metadata locking subsystem to use mutex per lock and

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condition variable per context instead of one mutex and one conditional
variable for the whole subsystem.

This should increase concurrency in this subsystem.

It also opens the way for further changes which are necessary to solve
such bugs as bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock"
and bug #37346 "innodb does not detect deadlock between update and alter
table".

Two other notable changes done by this patch:

- MDL subsystem no longer implicitly acquires global intention exclusive
  metadata lock when per-object metadata lock is acquired. Now this has
  to be done by explicit calls outside of MDL subsystem.
- Instead of using separate MDL_context for opening system tables/tables
  for purposes of I_S we now create MDL savepoint in the main context
  before opening tables and rollback to this savepoint after closing
  them. This means that it is now possible to get ER_LOCK_DEADLOCK error
  even not inside a transaction. This might happen in unlikely case when
  one runs DDL on one of system tables while also running DDL on some
  other tables. Cases when this ER_LOCK_DEADLOCK error is not justified
  will be addressed by advanced deadlock detector for MDL subsystem which
  we plan to implement.
This commit is contained in:
Dmitry Lenev
2010-01-21 23:43:03 +03:00
parent c005126107
commit a63f8480db
24 changed files with 1595 additions and 848 deletions
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40
mysql-test/include/handler.inc
View File

@@ -543,7 +543,7 @@ disconnect flush;
#
--disable_warnings
drop table if exists t1,t2;
drop table if exists t1, t0;
--enable_warnings
create table t1 (c1 int);
--echo connection: default
@@ -552,31 +552,31 @@ handler t1 read first;
connect (flush,localhost,root,,);
connection flush;
--echo connection: flush
--send rename table t1 to t2;
--send rename table t1 to t0;
connection waiter;
--echo connection: waiter
let $wait_condition=
select count(*) = 1 from information_schema.processlist
where state = "Waiting for table" and info = "rename table t1 to t2";
where state = "Waiting for table" and info = "rename table t1 to t0";
--source include/wait_condition.inc
connection default;
--echo connection: default
--echo #
--echo # RENAME placed two pending locks and waits.
--echo # When HANDLER t2 OPEN does open_tables(), it calls
--echo # When HANDLER t0 OPEN does open_tables(), it calls
--echo # mysql_ha_flush(), which in turn closes the open HANDLER for t1.
--echo # RENAME TABLE gets unblocked. If it gets scheduled quickly
--echo # and manages to complete before open_tables()
--echo # of HANDLER t2 OPEN, open_tables() and therefore the whole
--echo # HANDLER t2 OPEN succeeds. Otherwise open_tables()
--echo # of HANDLER t0 OPEN, open_tables() and therefore the whole
--echo # HANDLER t0 OPEN succeeds. Otherwise open_tables()
--echo # notices a pending or active exclusive metadata lock on t2
--echo # and the whole HANDLER t2 OPEN fails with ER_LOCK_DEADLOCK
--echo # and the whole HANDLER t0 OPEN fails with ER_LOCK_DEADLOCK
--echo # error.
--echo #
--error 0, ER_LOCK_DEADLOCK
handler t2 open;
handler t0 open;
--error 0, ER_UNKNOWN_TABLE
handler t2 close;
handler t0 close;
--echo connection: flush
connection flush;
reap;
@@ -585,7 +585,7 @@ handler t1 read next;
--error ER_UNKNOWN_TABLE
handler t1 close;
connection default;
drop table t2;
drop table t0;
connection flush;
disconnect flush;
--source include/wait_until_disconnected.inc
@@ -972,35 +972,29 @@ connection default;
--echo #
create table t1 (a int, key a (a));
insert into t1 (a) values (1), (2), (3), (4), (5);
create table t2 (a int, key a (a));
insert into t2 (a) values (1), (2), (3), (4), (5);
create table t0 (a int, key a (a));
insert into t0 (a) values (1), (2), (3), (4), (5);
begin;
select * from t1;
--echo # --> connection con1
connection con1;
lock table t2 read;
--echo # --> connection con2
connection con2;
--echo # Sending:
send rename table t2 to t3, t1 to t2, t3 to t1;
send rename table t0 to t3, t1 to t0, t3 to t1;
--echo # --> connection con1
connection con1;
--echo # Waiting for 'rename table ...' to get blocked...
let $wait_condition=select count(*)=1 from information_schema.processlist
where state='Waiting for table' and info='rename table t2 to t3, t1 to t2, t3 to t1';
where state='Waiting for table' and info='rename table t0 to t3, t1 to t0, t3 to t1';
--source include/wait_condition.inc
--echo # --> connection default
connection default;
--error ER_LOCK_DEADLOCK
handler t2 open;
handler t0 open;
--error ER_LOCK_DEADLOCK
select * from t2;
select * from t0;
handler t1 open;
commit;
handler t1 close;
--echo # --> connection con1
connection con1;
unlock tables;
--echo # --> connection con2
connection con2;
--echo # Reaping 'rename table ...'...
@@ -1010,7 +1004,7 @@ connection default;
handler t1 open;
handler t1 read a prev;
handler t1 close;
drop table t2;
drop table t0;
--echo #
--echo # Originally there was a deadlock error in this test.
--echo # With implementation of deadlock detector