MySQL crashed unexpectedly

[sevmax]

Hello dear community!
Please help me to find the reason of issue below.
MySQL 5.5.8 server unexepectedly crashed twice during week after year of stable working.
Below is log, all repeats were replaced by points.
Thank you in advance for your help!

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110925 3:48:15 INNODB MONITOR OUTPUT
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Per second averages calculated from the last 53 seconds
-----------------
BACKGROUND THREAD
-----------------
srv_master_thread loops: 188178 1_second, 186777 sleeps, 18817 10_second, 0 background, 0 flush
srv_master_thread log flush and writes: 189740
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SEMAPHORES
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OS WAIT ARRAY INFO: reservation count 206130, signal count 505641
--Thread 1495927104 has waited at /builddir/build/BUILD/mysql-5.5.8/storage/innobase/trx/trx0trx.c line 991 for 4.00 seconds the semaphore:
Mutex at 0x1546e928 created file /builddir/build/BUILD/mysql-5.5.8/storage/innobase/srv/srv0srv.c line 996, lock var 1
waiters flag 1
....................
Mutex spin waits 23844309, rounds 23744956, OS waits 162736
RW-shared spins 147070, rounds 1329982, OS waits 37121
RW-excl spins 25588, rounds 546053, OS waits 3731
Spin rounds per wait: 1.00 mutex, 9.04 RW-shared, 21.34 RW-excl
FAIL TO OBTAIN KERNEL MUTEX, SKIP LOCK INFO PRINTING
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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: 1 [0, 0, 1, 0] ,
ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
Pending flushes (fsync) log: 0; buffer pool: 0
1024362 OS file reads, 16310018 OS file writes, 894447 OS fsyncs
0.01 reads/s, 16384 avg bytes/read, 2.10 writes/s, 0.15 fsyncs/s
-------------------------------------
INSERT BUFFER AND ADAPTIVE HASH INDEX
-------------------------------------
Ibuf: size 1, free list len 4928, seg size 4930, 15846 merges
merged operations:
insert 9681, delete mark 9659, delete 659
discarded operations:
insert 0, delete mark 0, delete 0
Hash table size 51879403, node heap has 33190 buffer(s)
28934.06 hash searches/s, 9599.44 non-hash searches/s
---
LOG
---
Log sequence number 717496304542
Log flushed up to 717496303172
Last checkpoint at 717488519443
0 pending log writes, 0 pending chkp writes
10354733 log i/o's done, 0.06 log i/o's/second
----------------------
BUFFER POOL AND MEMORY
----------------------
Total memory allocated 26828800000; in additional pool allocated 0
Dictionary memory allocated 502834
Buffer pool size 1599999
Free buffers 531045
Database pages 1035764
Old database pages 382362
Modified db pages 4660
Pending reads 0
Pending writes: LRU 0, flush list 127, single page 0
Pages made young 1989, not young 0
0.00 youngs/s, 0.00 non-youngs/s
Pages read 1024317, created 11447, written 5732938
0.01 reads/s, 0.00 creates/s, 1.96 writes/s
Buffer pool hit rate 1000 / 1000, young-making rate 0 / 1000 not 0 / 1000
Pages read ahead 0.00/s, evicted without access 0.00/s
LRU len: 1035764, unzip_LRU len: 0
I/O sum[0]:cur[131], unzip sum[0]:cur[0]
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ROW OPERATIONS
--------------
0 queries inside InnoDB, 0 queries in queue
14 read views open inside InnoDB
Main thread process no. 4830, id 1198483776, state: making checkpoint
Number of rows inserted 127217, updated 5027457, deleted 7700, read 286840879392
0.04 inserts/s, 0.89 updates/s, 0.00 deletes/s, 94475.92 reads/s
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END OF INNODB MONITOR OUTPUT
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