innodb.innodb_sys_semaphore_waits and sys_vars.innodb_fatal_semaphore_wait_threshold fail sporadically in buildbot

innodb.innodb_sys_semaphore_waits 'innodb_plugin' w4 [ fail ]

        Test ended at 2015-03-30 02:15:30

CURRENT_TEST: innodb.innodb_sys_semaphore_waits

mysqltest: At line 98: Server failed to dissapear

The result from queries just before the failure was:

< snip >

# Establish connection con2 (user=root)

drop table if exists t1;

# Switch to connection con1

create table t1 (id integer, x integer) engine = InnoDB;

insert into t1 values(0, 0);

set DEBUG_DBUG='+d,fatal-semaphore-timeout';

set autocommit=0;

# Sending query on con1,

# the session will hold lock table mutex and sleep

SELECT * from t1 where id = 0 FOR UPDATE;

# Switch to connection con2

set autocommit=0;

# Sending query on con2,

# the session will be blocked on the lock table mutex and

# thus be put into sync arry

SELECT * from t1 where id = 0 FOR UPDATE;

# Switched to the default connection

# Waitting for mysqld to crash

More results from queries before failure can be found in /run/shm/var_auto_Slb6/4/log/innodb_sys_semaphore_waits.log