tokudb.locks-select-update-3 failed in buildbot with lock wait timeout

tokudb.locks-select-update-3             w2 [ fail ]

        Test ended at 2016-10-26 04:25:57

CURRENT_TEST: tokudb.locks-select-update-3

mysqltest: At line 27: query 'reap' failed: 1205: Lock wait timeout exceeded; try restarting transaction

The result from queries just before the failure was:

SET DEFAULT_STORAGE_ENGINE='tokudb';

drop table if exists t;

create table t (a int primary key, b int);

insert into t values (1,0);

set session transaction isolation level read committed;

begin;

select * from t where a=1 for update;

a	b

1	0

update t set b=b+1 where a=1;

set session transaction isolation level read committed;

begin;

select * from t where a=1 for update;

commit;