mysql 每几个小时就重启，求指点

mysql 版本是5.1.60

err log如下
150524 8:55:44 - mysqld got signal 11 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help diagnose
the problem, but since we have already crashed, something is definitely wrong
and this may fail.

key_buffer_size=16777216
read_buffer_size=262144
max_used_connections=5
max_threads=151
threads_connected=1
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 133912 K
bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x1d885d0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stackbottom = 0x7f53d14f3cf0 thread_stack 0x40000
[0x6895a4]
[0x4bdd6b]
[0x62b440]
/lib/x86_64-linux-gnu/libc.so.6(get_nprocs+0x10d) [0x7f53d2e2a4ed]
/lib/x86_64-linux-gnu/libc.so.6(+0x7f13e) [0x7f53d2db713e]
/lib/x86_64-linux-gnu/libc.so.6(_libc_malloc+0x1ab) [0x7f53d2dbb0fb]
/lib/x86_64-linux-gnu/libc.so.6(+0x6f20b) [0x7f53d2da720b]
/lib/x86_64-linux-gnu/libnss_files.so.2(_nss_files_gethostbyaddr_r+0x1bb) [0x7f53d260050b]
[0x7ad740]
[0x7ad4c6]
[0x4c49dc]
[0x4c5f00]
[0x4c670f]
[0x62763a]
[0x7a9b89]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query ((nil)): is an invalid pointer
Connection ID (thread ID): 630
Status: NOT_KILLED