Disabling innodb_thread_concurrency might cause queries to hang

[Raghavendra D Prabhu]

lp:702165 seems to be fixed in PS (there is no fix attached to issue though), however, http://bugs.mysql.com/bug.php?id=68876 seems to be reported again with a test case. So it would be better to reverify this again.

[Laurynas Biveinis (laurynas-biveinis)]

Bug 702165 is http://bugs.mysql.com/bug.php?id=40760, this bug is http://bugs.mysql.com/bug.php?id=68876, these are two different bugs.

[Valerii Kravchuk (valerii-kravchuk)]

Test case from the upstream bug report hangs perfectly on Debug build of Percona-Server-5.5.30-rel30.2.

[Valerii Kravchuk (valerii-kravchuk)]

This is what we have in PS 5.6.10:

[openxs@chief mysql-test]$ ./mtr bug68876
Logging: ./mtr bug68876
2013-05-15 13:04:58 0 [Warning] Changed limits: max_open_files: 1024 max_connections: 151 table_cache: 431
2013-05-15 13:04:58 1196 [Note] Plugin 'FEDERATED' is disabled.
2013-05-15 13:04:58 1196 [Note] Binlog end
2013-05-15 13:04:58 1196 [Note] Shutting down plugin 'CSV'
2013-05-15 13:04:58 1196 [Note] Shutting down plugin 'MyISAM'
MySQL Version 5.6.10
Checking supported features...
 - SSL connections supported
 - binaries are debug compiled
Collecting tests...
Removing old var directory...
Creating var directory '/home/openxs/bzr2/percona-5.6/Percona-Server/mysql-test/var'...
Installing system database...
Using server port 46495

==============================================================================

TEST RESULT TIME (ms) or COMMENT
--------------------------------------------------------------------------

worker[1] Using MTR_BUILD_THREAD 300, with reserved ports 13000..13009
main.bug68876 [ fail ]
        Test ended at 2013-05-15 13:05:39

CURRENT_TEST: main.bug68876
mysqltest: In included file "./include/wait_condition.inc":
included from ./include/wait_condition.inc at line 60:
At line 60: Timeout in wait_condition.inc for $wait_condition

The result from queries just before the failure was:
< snip >
SET GLOBAL innodb_thread_concurrency = 1;
BEGIN;
SELECT * FROM t1 WHERE a = 1;
a b
1 1
BEGIN;
SELECT * FROM t1 WHERE a = 1;
a b
1 1
SET DEBUG_SYNC='innodb_row_update_for_mysql_begin SIGNAL inside_innodb WAIT_FOR go';
UPDATE t1 SET b = b + 1 WHERE a = 2;
SET DEBUG_SYNC='now WAIT_FOR inside_innodb';
SELECT * FROM t1 WHERE a = 3;
...

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-653