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Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
#
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
# Test how we handle locking in various cases when
# we read data from MyISAM tables.
#
# In this test we mostly check that the SQL-layer correctly
# determines the type of thr_lock.c lock for a table being
# read.
# I.e. that it disallows concurrent inserts when the statement
# is going to be written to the binary log and therefore
# should be serialized, and allows concurrent inserts when
# such serialization is not necessary (e.g. when
# the statement is not written to binary log).
#
# Force concurrent inserts to be performed even if the table
# has gaps. This allows to simplify clean up in scripts
# used below (instead of backing up table being inserted
# into and then restoring it from backup at the end of the
# script we can simply delete rows which were inserted).
set @old_concurrent_insert= @@global.concurrent_insert;
set @@global.concurrent_insert= 2;
select @@global.concurrent_insert;
@@global.concurrent_insert
ALWAYS
# Prepare playground by creating tables, views,
# routines and triggers used in tests.
drop table if exists t0, t1, t2, t3, t4, t5;
drop view if exists v1, v2;
drop procedure if exists p1;
drop procedure if exists p2;
drop function if exists f1;
drop function if exists f2;
drop function if exists f3;
drop function if exists f4;
drop function if exists f5;
drop function if exists f6;
drop function if exists f7;
drop function if exists f8;
drop function if exists f9;
drop function if exists f10;
drop function if exists f11;
drop function if exists f12;
drop function if exists f13;
drop function if exists f14;
drop function if exists f15;
create table t1 (i int primary key);
insert into t1 values (1), (2), (3), (4), (5);
create table t2 (j int primary key);
insert into t2 values (1), (2), (3), (4), (5);
create table t3 (k int primary key);
insert into t3 values (1), (2), (3);
create table t4 (l int primary key);
insert into t4 values (1);
create table t5 (l int primary key);
insert into t5 values (1);
create view v1 as select i from t1;
create view v2 as select j from t2 where j in (select i from t1);
create procedure p1(k int) insert into t2 values (k);
create function f1() returns int
begin
declare j int;
select i from t1 where i = 1 into j;
return j;
end|
create function f2() returns int
begin
declare k int;
select i from t1 where i = 1 into k;
insert into t2 values (k + 5);
return 0;
end|
create function f3() returns int
begin
return (select i from t1 where i = 3);
end|
create function f4() returns int
begin
if (select i from t1 where i = 3) then
return 1;
else
return 0;
end if;
end|
create function f5() returns int
begin
insert into t2 values ((select i from t1 where i = 1) + 5);
return 0;
end|
create function f6() returns int
begin
declare k int;
select i from v1 where i = 1 into k;
return k;
end|
create function f7() returns int
begin
declare k int;
select j from v2 where j = 1 into k;
return k;
end|
create function f8() returns int
begin
declare k int;
select i from v1 where i = 1 into k;
insert into t2 values (k+5);
return k;
end|
create function f9() returns int
begin
update v2 set j=j+10 where j=1;
return 1;
end|
create function f10() returns int
begin
return f1();
end|
create function f11() returns int
begin
declare k int;
set k= f1();
insert into t2 values (k+5);
return k;
end|
create function f12(p int) returns int
begin
insert into t2 values (p);
return p;
end|
create function f13(p int) returns int
begin
return p;
end|
create procedure p2(inout p int)
begin
select i from t1 where i = 1 into p;
end|
create function f14() returns int
begin
declare k int;
call p2(k);
insert into t2 values (k+5);
return k;
end|
create function f15() returns int
begin
declare k int;
call p2(k);
return k;
end|
create trigger t4_bi before insert on t4 for each row
begin
declare k int;
select i from t1 where i=1 into k;
set new.l= k+1;
end|
create trigger t4_bu before update on t4 for each row
begin
if (select i from t1 where i=1) then
set new.l= 2;
end if;
end|
create trigger t4_bd before delete on t4 for each row
begin
if !(select i from v1 where i=1) then
signal sqlstate '45000';
end if;
end|
create trigger t5_bi before insert on t5 for each row
begin
set new.l= f1()+1;
end|
create trigger t5_bu before update on t5 for each row
begin
declare j int;
call p2(j);
set new.l= j + 1;
end|
#
# Set common variables to be used by the scripts
# called below.
#
# Switch to connection 'con1'.
# Cache all functions used in the tests below so statements
# calling them won't need to open and lock mysql.proc table
# and we can assume that each statement locks its tables
# once during its execution.
show create procedure p1;
show create procedure p2;
show create function f1;
show create function f2;
show create function f3;
show create function f4;
show create function f5;
show create function f6;
show create function f7;
show create function f8;
show create function f9;
show create function f10;
show create function f11;
show create function f12;
show create function f13;
show create function f14;
show create function f15;
# Switch back to connection 'default'.
#
# 1. Statements that read tables and do not use subqueries.
#
#
# 1.1 Simple SELECT statement.
#
# No locks are necessary as this statement won't be written
# to the binary log and thanks to how MyISAM works SELECT
# will see version of the table prior to concurrent insert.
Success: 'select * from t1' allows concurrent inserts into 't1'.
#
# 1.2 Multi-UPDATE statement.
#
# Has to take shared locks on rows in the table being read as this
# statement will be written to the binary log and therefore should
# be serialized with concurrent statements.
Success: 'update t2, t1 set j= j - 1 where i = j' doesn't allow concurrent inserts into 't1'.
#
# 1.3 Multi-DELETE statement.
#
# The above is true for this statement as well.
Success: 'delete t2 from t1, t2 where i = j' doesn't allow concurrent inserts into 't1'.
#
# 1.4 DESCRIBE statement.
#
# This statement does not really read data from the
# target table and thus does not take any lock on it.
# We check this for completeness of coverage.
lock table t1 write;
# Switching to connection 'con1'.
# This statement should not be blocked.
describe t1;
# Switching to connection 'default'.
unlock tables;
#
# 1.5 SHOW statements.
#
# The above is true for SHOW statements as well.
lock table t1 write;
# Switching to connection 'con1'.
# These statements should not be blocked.
show keys from t1;
# Switching to connection 'default'.
unlock tables;
#
# 2. Statements which read tables through subqueries.
#
#
# 2.1 CALL with a subquery.
#
# A strong lock is not necessary as this statement is not
# written to the binary log as a whole (it is written
# statement-by-statement).
Success: 'call p1((select i + 5 from t1 where i = 1))' allows concurrent inserts into 't1'.
#
# 2.2 CREATE TABLE with a subquery.
#
# Has to take a strong lock on the table being read as
# this statement is written to the binary log and therefore
# should be serialized with concurrent statements.
Success: 'create table t0 select * from t1' doesn't allow concurrent inserts into 't1'.
drop table t0;
Success: 'create table t0 select j from t2 where j in (select i from t1)' doesn't allow concurrent inserts into 't1'.
drop table t0;
#
# 2.3 DELETE with a subquery.
#
# The above is true for this statement as well.
Success: 'delete from t2 where j in (select i from t1)' doesn't allow concurrent inserts into 't1'.
#
# 2.4 MULTI-DELETE with a subquery.
#
# Same is true for this statement as well.
Success: 'delete t2 from t3, t2 where k = j and j in (select i from t1)' doesn't allow concurrent inserts into 't1'.
#
# 2.5 DO with a subquery.
#
# A strong lock is not necessary as it is not logged.
Success: 'do (select i from t1 where i = 1)' allows concurrent inserts into 't1'.
#
# 2.6 INSERT with a subquery.
#
# Has to take a strong lock on the table being read as
# this statement is written to the binary log and therefore
# should be serialized with concurrent inserts.
Success: 'insert into t2 select i+5 from t1' doesn't allow concurrent inserts into 't1'.
Success: 'insert into t2 values ((select i+5 from t1 where i = 4))' doesn't allow concurrent inserts into 't1'.
#
# 2.7 LOAD DATA with a subquery.
#
# The above is true for this statement as well.
Success: 'load data infile '../../std_data/rpl_loaddata.dat' into table t2 (@a, @b) set j= @b + (select i from t1 where i = 1)' doesn't allow concurrent inserts into 't1'.
#
# 2.8 REPLACE with a subquery.
#
# Same is true for this statement as well.
Success: 'replace into t2 select i+5 from t1' doesn't allow concurrent inserts into 't1'.
Success: 'replace into t2 values ((select i+5 from t1 where i = 4))' doesn't allow concurrent inserts into 't1'.
#
# 2.9 SELECT with a subquery.
#
# Strong locks are not necessary as this statement is not written
# to the binary log and thanks to how MyISAM works this statement
# sees a version of the table prior to the concurrent insert.
Success: 'select * from t2 where j in (select i from t1)' allows concurrent inserts into 't1'.
#
# 2.10 SET with a subquery.
#
# The same is true for this statement as well.
Success: 'set @a:= (select i from t1 where i = 1)' allows concurrent inserts into 't1'.
#
# 2.11 SHOW with a subquery.
#
# And for this statement too.
Success: 'show tables from test where Tables_in_test = 't2' and (select i from t1 where i = 1)' allows concurrent inserts into 't1'.
Success: 'show columns from t2 where (select i from t1 where i = 1)' allows concurrent inserts into 't1'.
#
# 2.12 UPDATE with a subquery.
#
# Has to take a strong lock on the table being read as
# this statement is written to the binary log and therefore
# should be serialized with concurrent inserts.
Success: 'update t2 set j= j-10 where j in (select i from t1)' doesn't allow concurrent inserts into 't1'.
#
# 2.13 MULTI-UPDATE with a subquery.
#
# Same is true for this statement as well.
Success: 'update t2, t3 set j= j -10 where j=k and j in (select i from t1)' doesn't allow concurrent inserts into 't1'.
#
# 3. Statements which read tables through a view.
#
#
# 3.1 SELECT statement which uses some table through a view.
#
# Since this statement is not written to the binary log and
# an old version of the table is accessible thanks to how MyISAM
# handles concurrent insert, no locking is necessary.
Success: 'select * from v1' allows concurrent inserts into 't1'.
Success: 'select * from v2' allows concurrent inserts into 't1'.
Success: 'select * from t2 where j in (select i from v1)' allows concurrent inserts into 't1'.
Success: 'select * from t3 where k in (select j from v2)' allows concurrent inserts into 't1'.
#
# 3.2 Statements which modify a table and use views.
#
# Since such statements are going to be written to the binary
# log they need to be serialized against concurrent statements
# and therefore should take strong locks on the data read.
Success: 'update t2 set j= j-10 where j in (select i from v1)' doesn't allow concurrent inserts into 't1'.
Success: 'update t3 set k= k-10 where k in (select j from v2)' doesn't allow concurrent inserts into 't1'.
Success: 'update t2, v1 set j= j-10 where j = i' doesn't allow concurrent inserts into 't1'.
Success: 'update v2 set j= j-10 where j = 3' doesn't allow concurrent inserts into 't1'.
#
# 4. Statements which read tables through stored functions.
#
#
# 4.1 SELECT/SET with a stored function which does not
# modify data and uses SELECT in its turn.
#
# In theory there is no need to take strong locks on the table
# being selected from in SF as the call to such function
# won't get into the binary log. In practice, however, we
# discover that fact too late in the process to be able to
# affect the decision what locks should be taken.
# Hence, strong locks are taken in this case.
Success: 'select f1()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f1()' doesn't allow concurrent inserts into 't1'.
#
# 4.2 INSERT (or other statement which modifies data) with
# a stored function which does not modify data and uses
# SELECT.
#
# Since such statement is written to the binary log it should
# be serialized with concurrent statements affecting the data
# it uses. Therefore it should take strong lock on the data
# it reads.
Success: 'insert into t2 values (f1() + 5)' doesn't allow concurrent inserts into 't1'.
#
# 4.3 SELECT/SET with a stored function which
# reads and modifies data.
#
# Since a call to such function is written to the binary log,
# it should be serialized with concurrent statements affecting
# the data it uses. Hence, a strong lock on the data read
# should be taken.
Success: 'select f2()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f2()' doesn't allow concurrent inserts into 't1'.
#
# 4.4. SELECT/SET with a stored function which does not
# modify data and reads a table through subselect
# in a control construct.
#
# Again, in theory a call to this function won't get to the
# binary log and thus no strong lock is needed. But in practice
# we don't detect this fact early enough (get_lock_type_for_table())
# to avoid taking a strong lock.
Success: 'select f3()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f3()' doesn't allow concurrent inserts into 't1'.
Success: 'select f4()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f4()' doesn't allow concurrent inserts into 't1'.
#
# 4.5. INSERT (or other statement which modifies data) with
# a stored function which does not modify data and reads
# the table through a subselect in one of its control
# constructs.
#
# Since such statement is written to the binary log it should
# be serialized with concurrent statements affecting data it
# uses. Therefore it should take a strong lock on the data
# it reads.
Success: 'insert into t2 values (f3() + 5)' doesn't allow concurrent inserts into 't1'.
Success: 'insert into t2 values (f4() + 6)' doesn't allow concurrent inserts into 't1'.
#
# 4.6 SELECT/SET which uses a stored function with
# DML which reads a table via a subquery.
#
# Since call to such function is written to the binary log
# it should be serialized with concurrent statements.
# Hence reads should take a strong lock.
Success: 'select f5()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f5()' doesn't allow concurrent inserts into 't1'.
#
# 4.7 SELECT/SET which uses a stored function which
# doesn't modify data and reads tables through
# a view.
#
# Once again, in theory, calls to such functions won't
# get into the binary log and thus don't need strong
# locks. But in practice this fact is discovered
# too late to have any effect.
Success: 'select f6()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f6()' doesn't allow concurrent inserts into 't1'.
Success: 'select f7()' doesn't allow concurrent inserts into 't1'.
Success: 'set @a:= f7()' doesn't allow concurrent inserts into 't1'.
#
# 4.8 INSERT which uses stored function which
# doesn't modify data and reads a table
# through a view.
#
Bug#46947 "Embedded SELECT without FOR UPDATE is causing a lock" Update the result file to minor tweaks of the comments in the test case.
2010-04-28 15:43:25 +02:00
# Since such statement is written to the binary log and
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
# should be serialized with concurrent statements affecting
# the data it uses. Therefore it should take a strong lock on
# the table it reads.
Success: 'insert into t3 values (f6() + 5)' doesn't allow concurrent inserts into 't1'.
Success: 'insert into t3 values (f7() + 5)' doesn't allow concurrent inserts into 't1'.
#
Bug#46947 "Embedded SELECT without FOR UPDATE is causing a lock" Update the result file to minor tweaks of the comments in the test case.
2010-04-28 15:43:25 +02:00
# 4.9 SELECT which uses a stored function which
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
# modifies data and reads tables through a view.
#
# Since a call to such function is written to the binary log
# it should be serialized with concurrent statements.
# Hence, reads should take strong locks.
Success: 'select f8()' doesn't allow concurrent inserts into 't1'.
Success: 'select f9()' doesn't allow concurrent inserts into 't1'.
#
# 4.10 SELECT which uses a stored function which doesn't modify
# data and reads a table indirectly, by calling another
Bug#46947 "Embedded SELECT without FOR UPDATE is causing a lock" Update the result file to minor tweaks of the comments in the test case.
2010-04-28 15:43:25 +02:00
# function.
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
#
# In theory, calls to such functions won't get into the binary
# log and thus don't need to acquire strong locks. But in practice
# this fact is discovered too late to have any effect.
Success: 'select f10()' doesn't allow concurrent inserts into 't1'.
#
# 4.11 INSERT which uses a stored function which doesn't modify
# data and reads a table indirectly, by calling another
# function.
#
# Since such statement is written to the binary log, it should
# be serialized with concurrent statements affecting the data it
# uses. Therefore it should take strong locks on data it reads.
Success: 'insert into t2 values (f10() + 5)' doesn't allow concurrent inserts into 't1'.
#
# 4.12 SELECT which uses a stored function which modifies
# data and reads a table indirectly, by calling another
# function.
#
# Since a call to such function is written to the binary log
# it should be serialized from concurrent statements.
# Hence, read should take a strong lock.
Success: 'select f11()' doesn't allow concurrent inserts into 't1'.
#
# 4.13 SELECT that reads a table through a subquery passed
# as a parameter to a stored function which modifies
# data.
#
# Even though a call to this function is written to the
# binary log, values of its parameters are written as literals.
# So there is no need to acquire strong locks for tables used in
# the subquery.
Success: 'select f12((select i+10 from t1 where i=1))' allows concurrent inserts into 't1'.
#
# 4.14 INSERT that reads a table via a subquery passed
# as a parameter to a stored function which doesn't
# modify data.
#
# Since this statement is written to the binary log it should
# be serialized with concurrent statements affecting the data it
# uses. Therefore it should take strong locks on the data it reads.
Success: 'insert into t2 values (f13((select i+10 from t1 where i=1)))' doesn't allow concurrent inserts into 't1'.
#
# 5. Statements that read tables through stored procedures.
#
#
# 5.1 CALL statement which reads a table via SELECT.
#
# Since neither this statement nor its components are
# written to the binary log, there is no need to take
Bug#46947 "Embedded SELECT without FOR UPDATE is causing a lock" Update the result file to minor tweaks of the comments in the test case.
2010-04-28 15:43:25 +02:00
# strong locks on the data it reads.
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
Success: 'call p2(@a)' allows concurrent inserts into 't1'.
#
Yet another follow-up for the 5.5 version of fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock". Fixed comments in tests. Improved comments and performance of auxiliary scripts.
2010-05-30 11:27:44 +02:00
# 5.2 Function that modifies data and uses CALL,
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
# which reads a table through SELECT.
#
# Since a call to such function is written to the binary
# log, it should be serialized with concurrent statements.
# Hence, in this case reads should take strong locks on data.
Success: 'select f14()' doesn't allow concurrent inserts into 't1'.
#
# 5.3 SELECT that calls a function that doesn't modify data and
# uses a CALL statement that reads a table via SELECT.
#
# In theory, calls to such functions won't get into the binary
# log and thus don't need to acquire strong locks. But in practice
# this fact is discovered too late to have any effect.
Success: 'select f15()' doesn't allow concurrent inserts into 't1'.
#
# 5.4 INSERT which calls function which doesn't modify data and
# uses CALL statement which reads table through SELECT.
#
# Since such statement is written to the binary log it should
# be serialized with concurrent statements affecting data it
# uses. Therefore it should take strong locks on data it reads.
Success: 'insert into t2 values (f15()+5)' doesn't allow concurrent inserts into 't1'.
#
# 6. Statements that use triggers.
#
#
# 6.1 Statement invoking a trigger that reads table via SELECT.
#
# Since this statement is written to the binary log it should
# be serialized with concurrent statements affecting the data
# it uses. Therefore, it should take strong locks on the data
Bug#46947 "Embedded SELECT without FOR UPDATE is causing a lock" Update the result file to minor tweaks of the comments in the test case.
2010-04-28 15:43:25 +02:00
# it reads.
Committing on behalf or Dmitry Lenev: Fix for bug #46947 "Embedded SELECT without FOR UPDATE is causing a lock", with after-review fixes. SELECT statements with subqueries referencing InnoDB tables were acquiring shared locks on rows in these tables when they were executed in REPEATABLE-READ mode and with statement or mixed mode binary logging turned on. This was a regression which were introduced when fixing bug 39843. The problem was that for tables belonging to subqueries parser set TL_READ_DEFAULT as a lock type. In cases when statement/mixed binary logging at open_tables() time this type of lock was converted to TL_READ_NO_INSERT lock at open_tables() time and caused InnoDB engine to acquire shared locks on reads from these tables. Although in some cases such behavior was correct (e.g. for subqueries in DELETE) in case of SELECT it has caused unnecessary locking. This patch tries to solve this problem by rethinking our approach to how we handle locking for SELECT and subqueries. Now we always set TL_READ_DEFAULT lock type for all cases when we read data. When at open_tables() time this lock is interpreted as TL_READ_NO_INSERT or TL_READ depending on whether this statement as a whole or call to function which uses particular table should be written to the binary log or not (if yes then statement should be properly serialized with concurrent statements and stronger lock should be acquired). Test coverage is added for both InnoDB and MyISAM. This patch introduces an "incompatible" change in locking scheme for subqueries used in SELECT ... FOR UPDATE and SELECT .. IN SHARE MODE. In 4.1 the server would use a snapshot InnoDB read for subqueries in SELECT FOR UPDATE and SELECT .. IN SHARE MODE statements, regardless of whether the binary log is on or off. If the user required a different type of read (i.e. locking read), he/she could request so explicitly by providing FOR UPDATE/IN SHARE MODE clause for each individual subquery. On of the patches for 5.0 broke this behaviour (which was not documented or tested), and started to use locking reads fora all subqueries in SELECT ... FOR UPDATE/IN SHARE MODE. This patch restored 4.1 behaviour.
2010-04-28 12:04:11 +02:00
Success: 'insert into t4 values (2)' doesn't allow concurrent inserts into 't1'.
#
# 6.2 Statement invoking a trigger that reads table through
# a subquery in a control construct.
#
# The above is true for this statement as well.
Success: 'update t4 set l= 2 where l = 1' doesn't allow concurrent inserts into 't1'.
#
# 6.3 Statement invoking a trigger that reads a table through
# a view.
#
# And for this statement.
Success: 'delete from t4 where l = 1' doesn't allow concurrent inserts into 't1'.
#
# 6.4 Statement invoking a trigger that reads a table through
# a stored function.
#
# And for this statement.
Success: 'insert into t5 values (2)' doesn't allow concurrent inserts into 't1'.
#
# 6.5 Statement invoking a trigger that reads a table through
# stored procedure.
#
# And for this statement.
Success: 'update t5 set l= 2 where l = 1' doesn't allow concurrent inserts into 't1'.
# Clean-up.
drop function f1;
drop function f2;
drop function f3;
drop function f4;
drop function f5;
drop function f6;
drop function f7;
drop function f8;
drop function f9;
drop function f10;
drop function f11;
drop function f12;
drop function f13;
drop function f14;
drop function f15;
drop view v1, v2;
drop procedure p1;
drop procedure p2;
drop table t1, t2, t3, t4, t5;
set @@global.concurrent_insert= @old_concurrent_insert;
#
Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
# Test for bug #45143 "All connections hang on concurrent ALTER TABLE".
#
# Concurrent execution of statements which required weak write lock
# (TL_WRITE_ALLOW_WRITE) on several instances of the same table and
# statements which tried to acquire stronger write lock (TL_WRITE,
# TL_WRITE_ALLOW_READ) on this table might have led to deadlock.
drop table if exists t1;
Implement new type-of-operation-aware metadata locks. Add a wait-for graph based deadlock detector to the MDL subsystem. Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". The first bug manifested itself as an unwarranted abort of a transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER statement, when this transaction tried to repeat use of a table, which it has already used in a similar fashion before ALTER started. The second bug showed up as a deadlock between table-level locks and InnoDB row locks, which was "detected" only after innodb_lock_wait_timeout timeout. A transaction would start using the table and modify a few rows. Then ALTER TABLE would come in, and start copying rows into a temporary table. Eventually it would stumble on the modified records and get blocked on a row lock. The first transaction would try to do more updates, and get blocked on thr_lock.c lock. This situation of circular wait would only get resolved by a timeout. Both these bugs stemmed from inadequate solutions to the problem of deadlocks occurring between different locking subsystems. In the first case we tried to avoid deadlocks between metadata locking and table-level locking subsystems, when upgrading shared metadata lock to exclusive one. Transactions holding the shared lock on the table and waiting for some table-level lock used to be aborted too aggressively. We also allowed ALTER TABLE to start in presence of transactions that modify the subject table. ALTER TABLE acquires TL_WRITE_ALLOW_READ lock at start, and that block all writes against the table (naturally, we don't want any writes to be lost when switching the old and the new table). TL_WRITE_ALLOW_READ lock, in turn, would block the started transaction on thr_lock.c lock, should they do more updates. This, again, lead to the need to abort such transactions. The second bug occurred simply because we didn't have any mechanism to detect deadlocks between the table-level locks in thr_lock.c and row-level locks in InnoDB, other than innodb_lock_wait_timeout. This patch solves both these problems by moving lock conflicts which are causing these deadlocks into the metadata locking subsystem, thus making it possible to avoid or detect such deadlocks inside MDL. To do this we introduce new type-of-operation-aware metadata locks, which allow MDL subsystem to know not only the fact that transaction has used or is going to use some object but also what kind of operation it has carried out or going to carry out on the object. This, along with the addition of a special kind of upgradable metadata lock, allows ALTER TABLE to wait until all transactions which has updated the table to go away. This solves the second issue. Another special type of upgradable metadata lock is acquired by LOCK TABLE WRITE. This second lock type allows to solve the first issue, since abortion of table-level locks in event of DDL under LOCK TABLES becomes also unnecessary. Below follows the list of incompatible changes introduced by this patch: - From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those statements that acquire TL_WRITE_ALLOW_READ lock) wait for all transactions which has *updated* the table to complete. - From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE (i.e. all statements which acquire TL_WRITE table-level lock) wait for all transaction which *updated or read* from the table to complete. As a consequence, innodb_table_locks=0 option no longer applies to LOCK TABLES ... WRITE. - DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort statements or transactions which use tables being dropped or renamed, and instead wait for these transactions to complete. - Since LOCK TABLES WRITE now takes a special metadata lock, not compatible with with reads or writes against the subject table and transaction-wide, thr_lock.c deadlock avoidance algorithm that used to ensure absence of deadlocks between LOCK TABLES WRITE and other statements is no longer sufficient, even for MyISAM. The wait-for graph based deadlock detector of MDL subsystem may sometimes be necessary and is involved. This may lead to ER_LOCK_DEADLOCK error produced for multi-statement transactions even if these only use MyISAM: session 1: session 2: begin; update t1 ... lock table t2 write, t1 write; -- gets a lock on t2, blocks on t1 update t2 ... (ER_LOCK_DEADLOCK) - Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE was abandoned. LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same priority as the usual LOCK TABLE ... WRITE. SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in the wait queue. - We do not take upgradable metadata locks on implicitly locked tables. So if one has, say, a view v1 that uses table t1, and issues: LOCK TABLE v1 WRITE; FLUSH TABLE t1; -- (or just 'FLUSH TABLES'), an error is produced. In order to be able to perform DDL on a table under LOCK TABLES, the table must be locked explicitly in the LOCK TABLES list.
2010-02-01 12:43:06 +01:00
drop view if exists v1;
Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
# Create auxiliary connections used through the test.
# Reset DEBUG_SYNC facility before using it.
set debug_sync= 'RESET';
# Turn off logging so calls to locking subsystem performed
# for general_log table won't interfere with our test.
set @old_general_log = @@global.general_log;
set @@global.general_log= OFF;
create table t1 (i int) engine=InnoDB;
Implement new type-of-operation-aware metadata locks. Add a wait-for graph based deadlock detector to the MDL subsystem. Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". The first bug manifested itself as an unwarranted abort of a transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER statement, when this transaction tried to repeat use of a table, which it has already used in a similar fashion before ALTER started. The second bug showed up as a deadlock between table-level locks and InnoDB row locks, which was "detected" only after innodb_lock_wait_timeout timeout. A transaction would start using the table and modify a few rows. Then ALTER TABLE would come in, and start copying rows into a temporary table. Eventually it would stumble on the modified records and get blocked on a row lock. The first transaction would try to do more updates, and get blocked on thr_lock.c lock. This situation of circular wait would only get resolved by a timeout. Both these bugs stemmed from inadequate solutions to the problem of deadlocks occurring between different locking subsystems. In the first case we tried to avoid deadlocks between metadata locking and table-level locking subsystems, when upgrading shared metadata lock to exclusive one. Transactions holding the shared lock on the table and waiting for some table-level lock used to be aborted too aggressively. We also allowed ALTER TABLE to start in presence of transactions that modify the subject table. ALTER TABLE acquires TL_WRITE_ALLOW_READ lock at start, and that block all writes against the table (naturally, we don't want any writes to be lost when switching the old and the new table). TL_WRITE_ALLOW_READ lock, in turn, would block the started transaction on thr_lock.c lock, should they do more updates. This, again, lead to the need to abort such transactions. The second bug occurred simply because we didn't have any mechanism to detect deadlocks between the table-level locks in thr_lock.c and row-level locks in InnoDB, other than innodb_lock_wait_timeout. This patch solves both these problems by moving lock conflicts which are causing these deadlocks into the metadata locking subsystem, thus making it possible to avoid or detect such deadlocks inside MDL. To do this we introduce new type-of-operation-aware metadata locks, which allow MDL subsystem to know not only the fact that transaction has used or is going to use some object but also what kind of operation it has carried out or going to carry out on the object. This, along with the addition of a special kind of upgradable metadata lock, allows ALTER TABLE to wait until all transactions which has updated the table to go away. This solves the second issue. Another special type of upgradable metadata lock is acquired by LOCK TABLE WRITE. This second lock type allows to solve the first issue, since abortion of table-level locks in event of DDL under LOCK TABLES becomes also unnecessary. Below follows the list of incompatible changes introduced by this patch: - From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those statements that acquire TL_WRITE_ALLOW_READ lock) wait for all transactions which has *updated* the table to complete. - From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE (i.e. all statements which acquire TL_WRITE table-level lock) wait for all transaction which *updated or read* from the table to complete. As a consequence, innodb_table_locks=0 option no longer applies to LOCK TABLES ... WRITE. - DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort statements or transactions which use tables being dropped or renamed, and instead wait for these transactions to complete. - Since LOCK TABLES WRITE now takes a special metadata lock, not compatible with with reads or writes against the subject table and transaction-wide, thr_lock.c deadlock avoidance algorithm that used to ensure absence of deadlocks between LOCK TABLES WRITE and other statements is no longer sufficient, even for MyISAM. The wait-for graph based deadlock detector of MDL subsystem may sometimes be necessary and is involved. This may lead to ER_LOCK_DEADLOCK error produced for multi-statement transactions even if these only use MyISAM: session 1: session 2: begin; update t1 ... lock table t2 write, t1 write; -- gets a lock on t2, blocks on t1 update t2 ... (ER_LOCK_DEADLOCK) - Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE was abandoned. LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same priority as the usual LOCK TABLE ... WRITE. SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in the wait queue. - We do not take upgradable metadata locks on implicitly locked tables. So if one has, say, a view v1 that uses table t1, and issues: LOCK TABLE v1 WRITE; FLUSH TABLE t1; -- (or just 'FLUSH TABLES'), an error is produced. In order to be able to perform DDL on a table under LOCK TABLES, the table must be locked explicitly in the LOCK TABLES list.
2010-02-01 12:43:06 +01:00
# We have to use view in order to make LOCK TABLES avoid
# acquiring SNRW metadata lock on table.
create view v1 as select * from t1;
Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
insert into t1 values (1);
# Prepare user lock which will be used for resuming execution of
# the first statement after it acquires TL_WRITE_ALLOW_WRITE lock.
select get_lock("lock_bug45143_wait", 0);
get_lock("lock_bug45143_wait", 0)
1
# Switch to connection 'con_bug45143_1'.
# Sending:
insert into t1 values (get_lock("lock_bug45143_wait", 100));;
# Switch to connection 'con_bug45143_2'.
# Wait until the above INSERT takes TL_WRITE_ALLOW_WRITE lock on 't1'
# and then gets blocked on user lock 'lock_bug45143_wait'.
# Ensure that upcoming SELECT waits after acquiring TL_WRITE_ALLOW_WRITE
# lock for the first instance of 't1'.
set debug_sync='thr_multi_lock_after_thr_lock SIGNAL parked WAIT_FOR go';
# Sending:
select count(*) > 0 from t1 as a, t1 as b for update;;
# Switch to connection 'con_bug45143_3'.
# Wait until the above SELECT ... FOR UPDATE is blocked after
# acquiring lock for the the first instance of 't1'.
set debug_sync= 'now WAIT_FOR parked';
# Send LOCK TABLE statement which will try to get TL_WRITE lock on 't1':
Implement new type-of-operation-aware metadata locks. Add a wait-for graph based deadlock detector to the MDL subsystem. Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". The first bug manifested itself as an unwarranted abort of a transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER statement, when this transaction tried to repeat use of a table, which it has already used in a similar fashion before ALTER started. The second bug showed up as a deadlock between table-level locks and InnoDB row locks, which was "detected" only after innodb_lock_wait_timeout timeout. A transaction would start using the table and modify a few rows. Then ALTER TABLE would come in, and start copying rows into a temporary table. Eventually it would stumble on the modified records and get blocked on a row lock. The first transaction would try to do more updates, and get blocked on thr_lock.c lock. This situation of circular wait would only get resolved by a timeout. Both these bugs stemmed from inadequate solutions to the problem of deadlocks occurring between different locking subsystems. In the first case we tried to avoid deadlocks between metadata locking and table-level locking subsystems, when upgrading shared metadata lock to exclusive one. Transactions holding the shared lock on the table and waiting for some table-level lock used to be aborted too aggressively. We also allowed ALTER TABLE to start in presence of transactions that modify the subject table. ALTER TABLE acquires TL_WRITE_ALLOW_READ lock at start, and that block all writes against the table (naturally, we don't want any writes to be lost when switching the old and the new table). TL_WRITE_ALLOW_READ lock, in turn, would block the started transaction on thr_lock.c lock, should they do more updates. This, again, lead to the need to abort such transactions. The second bug occurred simply because we didn't have any mechanism to detect deadlocks between the table-level locks in thr_lock.c and row-level locks in InnoDB, other than innodb_lock_wait_timeout. This patch solves both these problems by moving lock conflicts which are causing these deadlocks into the metadata locking subsystem, thus making it possible to avoid or detect such deadlocks inside MDL. To do this we introduce new type-of-operation-aware metadata locks, which allow MDL subsystem to know not only the fact that transaction has used or is going to use some object but also what kind of operation it has carried out or going to carry out on the object. This, along with the addition of a special kind of upgradable metadata lock, allows ALTER TABLE to wait until all transactions which has updated the table to go away. This solves the second issue. Another special type of upgradable metadata lock is acquired by LOCK TABLE WRITE. This second lock type allows to solve the first issue, since abortion of table-level locks in event of DDL under LOCK TABLES becomes also unnecessary. Below follows the list of incompatible changes introduced by this patch: - From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those statements that acquire TL_WRITE_ALLOW_READ lock) wait for all transactions which has *updated* the table to complete. - From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE (i.e. all statements which acquire TL_WRITE table-level lock) wait for all transaction which *updated or read* from the table to complete. As a consequence, innodb_table_locks=0 option no longer applies to LOCK TABLES ... WRITE. - DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort statements or transactions which use tables being dropped or renamed, and instead wait for these transactions to complete. - Since LOCK TABLES WRITE now takes a special metadata lock, not compatible with with reads or writes against the subject table and transaction-wide, thr_lock.c deadlock avoidance algorithm that used to ensure absence of deadlocks between LOCK TABLES WRITE and other statements is no longer sufficient, even for MyISAM. The wait-for graph based deadlock detector of MDL subsystem may sometimes be necessary and is involved. This may lead to ER_LOCK_DEADLOCK error produced for multi-statement transactions even if these only use MyISAM: session 1: session 2: begin; update t1 ... lock table t2 write, t1 write; -- gets a lock on t2, blocks on t1 update t2 ... (ER_LOCK_DEADLOCK) - Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE was abandoned. LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same priority as the usual LOCK TABLE ... WRITE. SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in the wait queue. - We do not take upgradable metadata locks on implicitly locked tables. So if one has, say, a view v1 that uses table t1, and issues: LOCK TABLE v1 WRITE; FLUSH TABLE t1; -- (or just 'FLUSH TABLES'), an error is produced. In order to be able to perform DDL on a table under LOCK TABLES, the table must be locked explicitly in the LOCK TABLES list.
2010-02-01 12:43:06 +01:00
lock table v1 write;;
Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
# Switch to connection 'default'.
# Wait until this LOCK TABLES statement starts waiting for table lock.
# Allow SELECT ... FOR UPDATE to resume.
# Since it already has TL_WRITE_ALLOW_WRITE lock on the first instance
# of 't1' it should be able to get lock on the second instance without
# waiting, even although there is another thread which has such lock
# on this table and also there is a thread waiting for a TL_WRITE on it.
set debug_sync= 'now SIGNAL go';
# Switch to connection 'con_bug45143_2'.
# Reap SELECT ... FOR UPDATE
count(*) > 0
1
# Switch to connection 'default'.
# Resume execution of the INSERT statement.
select release_lock("lock_bug45143_wait");
release_lock("lock_bug45143_wait")
1
# Switch to connection 'con_bug45143_1'.
# Reap INSERT statement.
next-4284 tree: fix lock_sync.test failure in row based replication mode.
2010-02-11 17:10:34 +01:00
# In Statement and Mixed replication mode we get here "Unsafe
# for binlog" warnings. In row mode there are no warnings.
# Hide the discrepancy.
Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
# Switch to connection 'con_bug45143_3'.
# Reap LOCK TABLES statement.
unlock tables;
# Switch to connection 'default'.
# Do clean-up.
set debug_sync= 'RESET';
set @@global.general_log= @old_general_log;
Implement new type-of-operation-aware metadata locks. Add a wait-for graph based deadlock detector to the MDL subsystem. Fixes bug #46272 "MySQL 5.4.4, new MDL: unnecessary deadlock" and bug #37346 "innodb does not detect deadlock between update and alter table". The first bug manifested itself as an unwarranted abort of a transaction with ER_LOCK_DEADLOCK error by a concurrent ALTER statement, when this transaction tried to repeat use of a table, which it has already used in a similar fashion before ALTER started. The second bug showed up as a deadlock between table-level locks and InnoDB row locks, which was "detected" only after innodb_lock_wait_timeout timeout. A transaction would start using the table and modify a few rows. Then ALTER TABLE would come in, and start copying rows into a temporary table. Eventually it would stumble on the modified records and get blocked on a row lock. The first transaction would try to do more updates, and get blocked on thr_lock.c lock. This situation of circular wait would only get resolved by a timeout. Both these bugs stemmed from inadequate solutions to the problem of deadlocks occurring between different locking subsystems. In the first case we tried to avoid deadlocks between metadata locking and table-level locking subsystems, when upgrading shared metadata lock to exclusive one. Transactions holding the shared lock on the table and waiting for some table-level lock used to be aborted too aggressively. We also allowed ALTER TABLE to start in presence of transactions that modify the subject table. ALTER TABLE acquires TL_WRITE_ALLOW_READ lock at start, and that block all writes against the table (naturally, we don't want any writes to be lost when switching the old and the new table). TL_WRITE_ALLOW_READ lock, in turn, would block the started transaction on thr_lock.c lock, should they do more updates. This, again, lead to the need to abort such transactions. The second bug occurred simply because we didn't have any mechanism to detect deadlocks between the table-level locks in thr_lock.c and row-level locks in InnoDB, other than innodb_lock_wait_timeout. This patch solves both these problems by moving lock conflicts which are causing these deadlocks into the metadata locking subsystem, thus making it possible to avoid or detect such deadlocks inside MDL. To do this we introduce new type-of-operation-aware metadata locks, which allow MDL subsystem to know not only the fact that transaction has used or is going to use some object but also what kind of operation it has carried out or going to carry out on the object. This, along with the addition of a special kind of upgradable metadata lock, allows ALTER TABLE to wait until all transactions which has updated the table to go away. This solves the second issue. Another special type of upgradable metadata lock is acquired by LOCK TABLE WRITE. This second lock type allows to solve the first issue, since abortion of table-level locks in event of DDL under LOCK TABLES becomes also unnecessary. Below follows the list of incompatible changes introduced by this patch: - From now on, ALTER TABLE and CREATE/DROP TRIGGER SQL (i.e. those statements that acquire TL_WRITE_ALLOW_READ lock) wait for all transactions which has *updated* the table to complete. - From now on, LOCK TABLES ... WRITE, REPAIR/OPTIMIZE TABLE (i.e. all statements which acquire TL_WRITE table-level lock) wait for all transaction which *updated or read* from the table to complete. As a consequence, innodb_table_locks=0 option no longer applies to LOCK TABLES ... WRITE. - DROP DATABASE, DROP TABLE, RENAME TABLE no longer abort statements or transactions which use tables being dropped or renamed, and instead wait for these transactions to complete. - Since LOCK TABLES WRITE now takes a special metadata lock, not compatible with with reads or writes against the subject table and transaction-wide, thr_lock.c deadlock avoidance algorithm that used to ensure absence of deadlocks between LOCK TABLES WRITE and other statements is no longer sufficient, even for MyISAM. The wait-for graph based deadlock detector of MDL subsystem may sometimes be necessary and is involved. This may lead to ER_LOCK_DEADLOCK error produced for multi-statement transactions even if these only use MyISAM: session 1: session 2: begin; update t1 ... lock table t2 write, t1 write; -- gets a lock on t2, blocks on t1 update t2 ... (ER_LOCK_DEADLOCK) - Finally, support of LOW_PRIORITY option for LOCK TABLES ... WRITE was abandoned. LOCK TABLE ... LOW_PRIORITY WRITE from now on has the same priority as the usual LOCK TABLE ... WRITE. SELECT HIGH PRIORITY no longer trumps LOCK TABLE ... WRITE in the wait queue. - We do not take upgradable metadata locks on implicitly locked tables. So if one has, say, a view v1 that uses table t1, and issues: LOCK TABLE v1 WRITE; FLUSH TABLE t1; -- (or just 'FLUSH TABLES'), an error is produced. In order to be able to perform DDL on a table under LOCK TABLES, the table must be locked explicitly in the LOCK TABLES list.
2010-02-01 12:43:06 +01:00
drop view v1;
Fix for bug #45143 "All connections hang on concurrent ALTER TABLE". Concurrent execution of statements which require non-table-level write locks on several instances of the same table (such as SELECT ... FOR UPDATE which uses same InnoDB table twice or a DML statement which invokes trigger which tries to update same InnoDB table directly and through stored function) and statements which required table-level locks on this table (e.g. LOCK TABLE ... WRITE, ALTER TABLE, ...) might have resulted in a deadlock. The problem occured when a thread tried to acquire write lock (TL_WRITE_ALLOW_WRITE) on the table but had to wait since there was a pending write lock (TL_WRITE, TL_WRITE_ALLOW_READ) on this table and we failed to detect that this thread already had another instance of write lock on it (so in fact we were trying to acquire recursive lock) because there was also another thread holding write lock on the table (also TL_WRITE_ALLOW_WRITE). When the latter thread released its lock neither the first thread nor the thread trying to acquire TL_WRITE/TL_WRITE_ALLOW_READ were woken up (as table was still write locked by the first thread) so we ended up with a deadlock. This patch solves this problem by ensuring that thread which already has write lock on the table won't wait when it tries to acquire second write lock on the same table.
2009-10-26 20:38:03 +01:00
drop table t1;
Bug #50821 Deadlock between LOCK TABLES and ALTER TABLE This was a deadlock between ALTER TABLE and another DML statement (or LOCK TABLES ... READ). ALTER TABLE would wait trying to upgrade its lock to MDL_EXCLUSIVE and the DML statement would wait trying to acquire a TL_READ_NO_INSERT table level lock. This could happen if one connection first acquired a MDL_SHARED_READ lock on a table. In another connection ALTER TABLE is then started. ALTER TABLE eventually blocks trying to upgrade to MDL_EXCLUSIVE, but while holding a TL_WRITE_ALLOW_READ table level lock. If the first connection then tries to acquire TL_READ_NO_INSERT, it will block and we have a deadlock since neither connection can proceed. This patch fixes the problem by allowing TL_READ_NO_INSERT locks to be granted if another connection holds TL_WRITE_ALLOW_READ on the same table. This will allow the DML statement to proceed such that it eventually can release its MDL lock which in turn makes ALTER TABLE able to proceed. Note that TL_READ_NO_INSERT was already partially compatible with TL_WRITE_ALLOW_READ as the latter would be granted if the former lock was held. This patch just makes the opposite true as well. Also note that since ALTER TABLE takes an upgradable MDL lock, there will be no starvation of ALTER TABLE statements by statements acquiring TL_READ or TL_READ_NO_INSERT. Test case added to lock_sync.test.
2010-02-04 10:00:36 +01:00
#
# Bug#50821 Deadlock between LOCK TABLES and ALTER TABLE
#
DROP TABLE IF EXISTS t1, t2;
CREATE TABLE t1(id INT);
CREATE TABLE t2(id INT);
# Connection con2
START TRANSACTION;
SELECT * FROM t1;
id
# Connection default
# Sending:
ALTER TABLE t1 ADD COLUMN j INT;
# Connection con2
# This used to cause a deadlock.
INSERT INTO t2 SELECT * FROM t1;
COMMIT;
# Connection default
# Reaping ALTER TABLE t1 ADD COLUMN j INT
DROP TABLE t1, t2;
Bug #51391 Deadlock involving events during rqg_info_schema test This was a deadlock between CREATE/ALTER/DROP EVENT and a query accessing both the mysql.event table and I_S.GLOBAL_VARIABLES. The root of the problem was that the LOCK_event_metadata mutex was used to both protect the "event_scheduler" global system variable and the internal event data structures used by CREATE/ALTER/DROP EVENT. The deadlock would occur if CREATE/ALTER/DROP EVENT held LOCK_event_metadata while trying to open the mysql.event table, at the same time as the query had mysql.event open, trying to lock LOCK_event_metadata to access "event_scheduler". This bug was fixed in the scope of Bug#51160 by using only LOCK_global_system_variables to protect "event_scheduler". This makes it so that the query above won't lock LOCK_event_metadata, thereby preventing this deadlock from occuring. This patch contains no code changes. Test case added to lock_sync.test.
2010-04-15 14:14:28 +02:00
#
# Bug#51391 Deadlock involving events during rqg_info_schema test
#
CREATE EVENT e1 ON SCHEDULE EVERY 5 HOUR DO SELECT 1;
CREATE EVENT e2 ON SCHEDULE EVERY 5 HOUR DO SELECT 2;
# Connection con1
SET DEBUG_SYNC="before_lock_tables_takes_lock SIGNAL drop WAIT_FOR query";
# Sending:
DROP EVENT e1;;
# Connection default
SET DEBUG_SYNC="now WAIT_FOR drop";
SELECT name FROM mysql.event, INFORMATION_SCHEMA.GLOBAL_VARIABLES
WHERE definer = VARIABLE_VALUE;
name
SET DEBUG_SYNC="now SIGNAL query";
# Connection con1
# Reaping: DROP EVENT t1
# Connection default
DROP EVENT e2;
SET DEBUG_SYNC="RESET";
Bug #55930 Assertion `thd->transaction.stmt.is_empty() || thd->in_sub_stmt || (thd->state.. OPTIMIZE TABLE is not directly supported by InnoDB. Instead, recreate and analyze of the table is done. After recreate, the table is closed and locks are released before the table is reopened and locks re-acquired for the analyze phase. This assertion was triggered if OPTIMIZE TABLE failed to acquire thr_lock locks before starting the analyze phase. The assertion tests (among other things) that there no active statement transaction. However, as part of acquiring the thr_lock lock, external_lock() is called for InnoDB tables and this causes a statement transaction to be started. If thr_multi_lock() later fails (e.g. due to timeout), the failure handling code causes this assert to be triggered. This patch fixes the problem by doing rollback of the current statement transaction in case open_ltable (used by OPTIMIZE TABLE) fails to acquire thr_lock locks. Test case added to lock_sync.test.
2010-10-13 16:15:28 +02:00
#
# Bug#55930 Assertion `thd->transaction.stmt.is_empty() ||
# thd->in_sub_stmt || (thd->state..
#
DROP TABLE IF EXISTS t1;
CREATE TABLE t1(a INT) engine=InnoDB;
INSERT INTO t1 VALUES (1), (2);
# Connection con1
SET SESSION lock_wait_timeout= 1;
SET DEBUG_SYNC= 'ha_admin_open_ltable SIGNAL opti_recreate WAIT_FOR opti_analyze';
# Sending:
OPTIMIZE TABLE t1;
# Connection con2
SET DEBUG_SYNC= 'now WAIT_FOR opti_recreate';
SET DEBUG_SYNC= 'after_lock_tables_takes_lock SIGNAL thrlock WAIT_FOR release_thrlock';
# Sending:
INSERT INTO t1 VALUES (3);
# Connection default
SET DEBUG_SYNC= 'now WAIT_FOR thrlock';
SET DEBUG_SYNC= 'now SIGNAL opti_analyze';
# Connection con1
# Reaping: OPTIMIZE TABLE t1
Table Op Msg_type Msg_text
test.t1 optimize note Table does not support optimize, doing recreate + analyze instead
test.t1 optimize error Lock wait timeout exceeded; try restarting transaction
test.t1 optimize status Operation failed
Warnings:
Error 1205 Lock wait timeout exceeded; try restarting transaction
SET DEBUG_SYNC= 'now SIGNAL release_thrlock';
# Connection con2
# Reaping: INSERT INTO t1 VALUES (3)
# Connection default
DROP TABLE t1;
SET DEBUG_SYNC= 'RESET';
Bug #57130 crash in Item_field::print during SHOW CREATE TABLE or VIEW This crash could happen if SHOW CREATE VIEW indirectly failed to open a view due to failures to open underlying tables (or functions). Several such errors were hidden and converted to ER_VIEW_INVALID warnings to prevent exposing details of underlying tables for which the user have no privileges. However, with the changes introduced by the patch for Bug#52044, failing to open a view will cause opened tables, views and functions to be closed. Since the errors causing these failures were converted to warnings, SHOW CREATE VIEW would try to continue. This made it possible to try to access memory that had been freed, causing a crash. This patch fixes the problem by not closing opened tables, views and functions in these cases. This allows SHOW CREATE VIEW to continue and also prevents it from accessing freed memory. Test case added to lock_sync.test.
2010-11-03 16:47:32 +01:00
#
# Bug#57130 crash in Item_field::print during SHOW CREATE TABLE or VIEW
#
DROP TABLE IF EXISTS t1;
DROP VIEW IF EXISTS v1;
DROP FUNCTION IF EXISTS f1;
CREATE TABLE t1(a INT);
CREATE FUNCTION f1() RETURNS INTEGER RETURN 1;
CREATE VIEW v1 AS SELECT * FROM t1 WHERE f1() = 1;
DROP FUNCTION f1;
# Connection con1
SET DEBUG_SYNC= 'open_tables_after_open_and_process_table SIGNAL opened WAIT_FOR dropped EXECUTE 2';
# Sending:
SHOW CREATE VIEW v1;
# Connection con2
SET DEBUG_SYNC= 'now WAIT_FOR opened';
SET DEBUG_SYNC= 'now SIGNAL dropped';
SET DEBUG_SYNC= 'now WAIT_FOR opened';
# Sending:
FLUSH TABLES;
# Connection default
# Waiting for FLUSH TABLES to be blocked.
SET DEBUG_SYNC= 'now SIGNAL dropped';
# Connection con1
# Reaping: SHOW CREATE VIEW v1
View Create View character_set_client collation_connection
v1 CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select `t1`.`a` AS `a` from `t1` where (`f1`() = 1) latin1 latin1_swedish_ci
Warnings:
Warning 1356 View 'test.v1' references invalid table(s) or column(s) or function(s) or definer/invoker of view lack rights to use them
# Connection con2
# Reaping: FLUSH TABLES
# Connection default
SET DEBUG_SYNC= 'RESET';
DROP VIEW v1;
DROP TABLE t1;
Bug#19070633 - POSSIBLE ACCESS TO FREED MEMORY IN IS_FREE_LOCK() AND IS_USED_LOCK(). Analysis: ----------- In functions Item_func_is_free_lock::val_int() and Item_func_is_used_lock::val_int(), for the specified user lock name, pointer to its "User_level_lock" object is obtained from hash "hash_user_locks". Mutex "LOCK_user_locks" is acquired for this and released immediately. And we are accessing members of User_level_lock after releasing the mutex. If same user lock is deleted(released) from concurrent thread then accessing members results in invalid(freed) memory access issue. Deleting of user lock is also protected from the mutex "LOCK_user_locks". Since this mutex is released in "val_int" functions mentioned above, delete operation proceeds while concurrent thread tries to access its members. With the test case, valgrind reports invalid read issues in val_int functions. Fix: ----------- To fix this issue, in "val_int" function of classes "Item_func_is_free_lock" and "Item_func_is_used_lock", now releasing mutex "LOCK_user_locks" after accessing User_level_lock members.
2014-09-16 07:58:46 +02:00
#
# Bug#19070633 - POSSIBLE ACCESS TO FREED MEMORY IN IS_FREE_LOCK() AND IS_USED_LOCK().
#
# Verifying issue for IS_FREE_LOCK() function.
SELECT GET_LOCK("lock_19070633", 600);
GET_LOCK("lock_19070633", 600)
1
connect con1, localhost, root,,;
# Waiting after getting user level lock info and releasing mutex.
SET DEBUG_SYNC= 'after_getting_user_level_lock_info SIGNAL parked WAIT_FOR go';
# Sending: SELECT IS_FREE_LOCK("lock_19070633");
SELECT IS_FREE_LOCK("lock_19070633");
connection default;
SET DEBUG_SYNC= 'now WAIT_FOR parked';
SELECT RELEASE_LOCK("lock_19070633");
RELEASE_LOCK("lock_19070633")
1
# Signaling connection con1 after releasing the lock.
# Without fix, accessing user level lock info in con1 would result in
# crash or valgrind issue invalid read is reported.
SET DEBUG_SYNC= 'now SIGNAL go';
connection con1;
# Reaping: SELECT IS_FREE_LOCK("lock_19070633");
IS_FREE_LOCK("lock_19070633")
0
connection default;
# Verifying issue for IS_USED_LOCK() function.
SELECT GET_LOCK("lock_19070633", 600);
GET_LOCK("lock_19070633", 600)
1
connection con1;
# Waiting after getting user level lock info and releasing mutex.
SET DEBUG_SYNC= 'after_getting_user_level_lock_info SIGNAL parked WAIT_FOR go';
# Sending: SELECT IS_USED_LOCK("lock_19070633");
SELECT IS_USED_LOCK("lock_19070633");
connection default;
SET DEBUG_SYNC= 'now WAIT_FOR parked';
SELECT RELEASE_LOCK("lock_19070633");
RELEASE_LOCK("lock_19070633")
1
# Signaling connection con1 after releasing the lock.
# Without fix, accessing user level lock info in con1 would result in
# crash or valgrind issue invalid read is reported.
SET DEBUG_SYNC= 'now SIGNAL go';
connection con1;
# Reaping: SELECT IS_USED_LOCK("lock_19070633");
IS_USED_LOCK("lock_19070633")
#
connection default;
SET DEBUG_SYNC= 'RESET';
disconnect con1;
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