XtraDB thread never exits. Always in 'cleaning up'

MariaDB [(none)]> show full processlist\G

*************************** 1. row ***************************

      Id: 80

    User: root

    Host: localhost

      db: NULL

 Command: Query

    Time: 0

   State: init

    Info: show full processlist

Progress: 0.000

1 row in set (0.00 sec)

MariaDB [(none)]> show engine innodb status\G

*************************** 1. row ***************************

  Type: InnoDB

  Name:

Status:

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

2016-03-16 10:03:21 7ff7fc505700 INNODB MONITOR OUTPUT

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

Per second averages calculated from the last 25 seconds

-----------------

BACKGROUND THREAD

-----------------

srv_master_thread loops: 50 srv_active, 0 srv_shutdown, 673746 srv_idle

srv_master_thread log flush and writes: 673567

----------

SEMAPHORES

----------

OS WAIT ARRAY INFO: reservation count 118

OS WAIT ARRAY INFO: signal count 120

Mutex spin waits 2904, rounds 3613, OS waits 53

RW-shared spins 68, rounds 1956, OS waits 64

RW-excl spins 3, rounds 50, OS waits 1

Spin rounds per wait: 1.24 mutex, 28.76 RW-shared, 16.67 RW-excl

------------

TRANSACTIONS

------------

Trx id counter 5443238

Purge done for trx's n:o < 5443232 undo n:o < 0 state: running but idle

History list length 541

LIST OF TRANSACTIONS FOR EACH SESSION:

---TRANSACTION 0, not started

MySQL thread id 80, OS thread handle 0x7ff7fc505700, query id 2271 localhost root init

show engine innodb status

---TRANSACTION 0, not started

MySQL thread id 24, OS thread handle 0x7ff7ff267700, query id 174 cleaning up

--------

FILE I/O

--------

I/O thread 0 state: waiting for completed aio requests (insert buffer thread)

I/O thread 1 state: waiting for completed aio requests (log thread)

I/O thread 2 state: waiting for completed aio requests (read thread)

I/O thread 3 state: waiting for completed aio requests (read thread)

I/O thread 4 state: waiting for completed aio requests (read thread)

I/O thread 5 state: waiting for completed aio requests (read thread)

I/O thread 6 state: waiting for completed aio requests (write thread)

I/O thread 7 state: waiting for completed aio requests (write thread)

I/O thread 8 state: waiting for completed aio requests (write thread)

I/O thread 9 state: waiting for completed aio requests (write thread)

Pending normal aio reads: 0 [0, 0, 0, 0] , aio writes: 0 [0, 0, 0, 0] ,

 ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0

Pending flushes (fsync) log: 0; buffer pool: 0

2049 OS file reads, 621 OS file writes, 280 OS fsyncs

0.00 reads/s, 0 avg bytes/read, 0.00 writes/s, 0.00 fsyncs/s

-------------------------------------

INSERT BUFFER AND ADAPTIVE HASH INDEX

-------------------------------------

Ibuf: size 1, free list len 1842, seg size 1844, 0 merges

merged operations:

 insert 0, delete mark 0, delete 0

discarded operations:

 insert 0, delete mark 0, delete 0

0.00 hash searches/s, 0.00 non-hash searches/s

---

LOG

---

Log sequence number 225203203047

Log flushed up to   225203203047

Pages flushed up to 225203203047

Last checkpoint at  225203203047

Max checkpoint age    80354304

Checkpoint age target 77843232

Modified age          0

Checkpoint age        0

0 pending log writes, 0 pending chkp writes

201 log i/o's done, 0.00 log i/o's/second

----------------------

BUFFER POOL AND MEMORY

----------------------

Total memory allocated 138412032; in additional pool allocated 0

Total memory allocated by read views 200

Internal hash tables (constant factor + variable factor)

    Adaptive hash index 2561632         (2213368 + 348264)

    Page hash           139112 (buffer pool 0 only)

    Dictionary cache    2001389         (554768 + 1446621)

    File system         938224  (812272 + 125952)

    Lock system         333592  (332872 + 720)

    Recovery system     0       (0 + 0)

Dictionary memory allocated 1446621

Buffer pool size        8191

Buffer pool size, bytes 134201344

Free buffers            6575

Database pages          1595

Old database pages      607

Modified db pages       0

Percent of dirty pages(LRU & free pages): 0.000

Max dirty pages percent: 75.000

Pending reads 0

Pending writes: LRU 0, flush list 0, single page 0

Pages made young 0, not young 0

0.00 youngs/s, 0.00 non-youngs/s

Pages read 1572, created 23, written 369

0.00 reads/s, 0.00 creates/s, 0.00 writes/s

No buffer pool page gets since the last printout

Pages read ahead 0.00/s, evicted without access 0.00/s, Random read ahead 0.00/s

LRU len: 1595, unzip_LRU len: 0

I/O sum[0]:cur[0], unzip sum[0]:cur[0]

--------------

ROW OPERATIONS

--------------

0 queries inside InnoDB, 0 queries in queue

0 read views open inside InnoDB

0 RW transactions active inside InnoDB

0 RO transactions active inside InnoDB

0 out of 1000 descriptors used

Main thread process no. 3914, id 140702637872896, state: sleeping

Number of rows inserted 157, updated 37, deleted 850, read 188280

0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s

Number of system rows inserted 0, updated 0, deleted 0, read 0

0.00 inserts/s, 0.00 updates/s, 0.00 deletes/s, 0.00 reads/s

----------------------------

END OF INNODB MONITOR OUTPUT

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

1 row in set (0.00 sec)

MariaDB [(none)]>