150903  8:28:06 [ERROR] 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.

To report this bug, see http://kb.askmonty.org/en/reporting-bugs

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.

Server version: 10.0.21-MariaDB-1~precise-wsrep-log
key_buffer_size=8388608
read_buffer_size=1048576
max_used_connections=204
max_threads=802
thread_count=179
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1666845 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0x7fb6fb389008
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...
stack_bottom = 0x7fb7146dadd0 thread_stack 0x48000
/usr/sbin/mysqld(my_print_stacktrace+0x2b)[0xba3a0b]
/usr/sbin/mysqld(handle_fatal_signal+0x398)[0x747ac8]
/lib/x86_64-linux-gnu/libpthread.so.0(+0xfcb0)[0x7fb7a92fdcb0]
/usr/sbin/mysqld(_ZN8MDL_lock11Ticket_list13remove_ticketEP10MDL_ticket+0x11)[0x6aec21]
/usr/sbin/mysqld(_ZN8MDL_lock13remove_ticketEMS_NS_11Ticket_listEP10MDL_ticket+0x41)[0x6af181]
/usr/sbin/mysqld(_ZN11MDL_context27release_locks_stored_beforeE17enum_mdl_durationP10MDL_ticket+0x3a)[0x6b001a]
/usr/sbin/mysqld(_Z21mysql_execute_commandP3THD+0x88d)[0x5ddd4d]
/usr/sbin/mysqld[0x5e5797]
/usr/sbin/mysqld[0x5e6173]
/usr/sbin/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0x199b)[0x5e804b]
/usr/sbin/mysqld(_Z10do_commandP3THD+0x25a)[0x5e898a]
/usr/sbin/mysqld(_Z24do_handle_one_connectionP3THD+0x55b)[0x6a5e9b]
/usr/sbin/mysqld(handle_one_connection+0x42)[0x6a5f92]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x7e9a)[0x7fb7a92f5e9a]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d)[0x7fb7a799038d]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0x7fb715966020): SELECT `data` FROM `tablename` WHERE `id` = '0000000000000000000000000000'
Connection ID (thread ID): 26904
Status: NOT_KILLED

Optimizer switch: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,index_merge_sort_intersection=off,engine_condition_pushdown=off,index_condition_pushdown=on,derived
_merge=on,derived_with_keys=on,firstmatch=on,loosescan=on,materialization=on,in_to_exists=on,semijoin=on,partial_match_rowid_merge=on,partial_match_table_scan=on,subquery_cache=on,mrr=off,mrr_cost_based=off,
mrr_sort_keys=off,outer_join_with_cache=on,semijoin_with_cache=on,join_cache_incremental=on,join_cache_hashed=on,join_cache_bka=on,optimize_join_buffer_size=off,table_elimination=on,extended_keys=on,exists_t
o_in=on

The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.
Writing a core file

(gdb) bt full
#0  0x00007fb7a92faf8c in pthread_kill () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#1  0x0000000000747af2 in handle_fatal_signal ()
No symbol table info available.
#2  <signal handler called>
No symbol table info available.
#3  0x00000000006aec21 in MDL_lock::Ticket_list::remove_ticket(MDL_ticket*) ()
No symbol table info available.
#4  0x00000000006af181 in MDL_lock::remove_ticket(MDL_lock::Ticket_list MDL_lock::*, MDL_ticket*) ()
No symbol table info available.
#5  0x00000000006b001a in MDL_context::release_locks_stored_before(enum_mdl_duration, MDL_ticket*) ()
No symbol table info available.
#6  0x00000000005ddd4d in mysql_execute_command(THD*) ()
No symbol table info available.
#7  0x00000000005e5797 in ?? ()
No symbol table info available.
#8  0x00000000005e6173 in ?? ()
No symbol table info available.
#9  0x00000000005e804b in dispatch_command(enum_server_command, THD*, char*, unsigned int) ()
No symbol table info available.
#10 0x00000000005e898a in do_command(THD*) ()
No symbol table info available.
#11 0x00000000006a5e9b in do_handle_one_connection(THD*) ()
No symbol table info available.
#12 0x00000000006a5f92 in handle_one_connection ()
No symbol table info available.
#13 0x00007fb7a92f5e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#14 0x00007fb7a799038d in clone () from /lib/x86_64-linux-gnu/libc.so.6
No symbol table info available.
#15 0x0000000000000000 in ?? ()
No symbol table info available.
(gdb)