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Making FLUSH TABLES WITH READ LOCK block COMMITs of existing transactions,

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in a deadlock-free manner. This splits locking the global read lock in two steps.
This fixes a consequence of this bug, known as:
BUG#4953 'mysqldump --master-data may report incorrect binlog position if using InnoDB'
And a test.


sql/handler.cc:
  making COMMIT wait if FLUSH TABLES WITH READ LOCK happened.
sql/lock.cc:
  an additional stage so that FLUSH TABLES WITH READ LOCK blocks COMMIT:
  make_global_read_lock_block_commit():
  taking the global read lock is TWO steps (2nd step is optional; without
  it, COMMIT of existing transactions will be allowed):
  lock_global_read_lock() THEN make_global_read_lock_block_commit().
sql/mysql_priv.h:
  new argument to wait_if_global_read_lock()
sql/sql_class.h:
  THD::global_read_lock now an uint to reflect the 2 steps of global read lock (does not block COMMIT / does)
sql/sql_db.cc:
  update for new prototype
sql/sql_parse.cc:
  implementing the two steps of global read lock so that FLUSH TABLES WITH READ LOCK can block COMMIT without deadlocking with COMMITs.
This commit is contained in:
unknown
2004-08-20 16:35:23 +02:00
parent f758ada4bc
commit cd8054d431
9 changed files with 154 additions and 21 deletions
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49
mysql-test/t/flush_block_commit.test Normal file
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# Let's see if FLUSH TABLES WITH READ LOCK blocks COMMIT of existing
# transactions.
# We verify that we did not introduce a deadlock.
-- source include/have_innodb.inc
connect (con1,localhost,root,,);
connect (con2,localhost,root,,);
connect (con3,localhost,root,,);
connection con1;
drop table if exists t1;
create table t1 (a int) type=innodb;
# blocks COMMIT ?
begin;
insert into t1 values(1);
connection con2;
flush tables with read lock;
select * from t1;
connection con1;
send commit; # blocked by con2
sleep 1;
connection con2;
select * from t1; # verify con1 was blocked and data did not move
unlock tables;
connection con1;
reap;
# No deadlock ?
connection con1;
begin;
select * from t1 for update;
connection con2;
begin;
send select * from t1 for update; # blocked by con1
sleep 1;
connection con3;
send flush tables with read lock; # blocked by con2
connection con1;
commit; # should not be blocked by con3
connection con2;
reap;
connection con3;
reap;
unlock tables;
connection con1;
drop table t1;