140618 13:03:25 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
140618 13:03:25 [Note] InnoDB: Using mutexes to ref count buffer pool pages
140618 13:03:25 [Note] InnoDB: The InnoDB memory heap is disabled
140618 13:03:25 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
140618 13:03:25 [Note] InnoDB: Compressed tables use zlib 1.2.8
140618 13:03:25 [Note] InnoDB: Using Linux native AIO
140618 13:03:25 [Note] InnoDB: Using CPU crc32 instructions
140618 13:03:25 [Note] InnoDB: Initializing buffer pool, size = 512.0M
140618 13:03:25 [Note] InnoDB: Completed initialization of buffer pool
140618 13:03:25 [Note] InnoDB: Highest supported file format is Barracuda.
140618 13:03:25 [Note] InnoDB: 128 rollback segment(s) are active.
140618 13:03:25 [Note] InnoDB: Waiting for purge to start
140618 13:03:25 [Note] InnoDB:  Percona XtraDB (http://www.percona.com) 5.6.17-65.0 started; log sequence number 134020202
140618 13:03:25 [Note] Plugin 'FEEDBACK' is disabled.
140618 13:03:25 [Note] CONNECT: Version 1.02.0002 March 16, 2014
140618 13:03:25 [Note] Server socket created on IP: '127.0.0.1'.
140618 13:03:25 [Note] Event Scheduler: Loaded 0 events
140618 13:03:25 [Note] /usr/libexec/mysqld: ready for connections.
Version: '10.0.12-MariaDB'  socket: '/var/lib/mysql/mysql.sock'  port: 3306  MariaDB Server
140618 13:07:22 [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: 10.0.12-MariaDB
key_buffer_size=134217728
read_buffer_size=131072
max_used_connections=23
max_threads=153
thread_count=23
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 467144 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0x7f529cce5928
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 = 0x7f525710bdc0 thread_stack 0x48000
/usr/libexec/mysqld(my_print_stacktrace+0x3d)[0x7f5298e42c0d]
/usr/libexec/mysqld(handle_fatal_signal+0x345)[0x7f52989b3e15]
/lib64/libpthread.so.0(+0xfe40)[0x7f5298052e40]
/usr/libexec/mysqld(+0x79b4f1)[0x7f5298c214f1]
/usr/libexec/mysqld(+0x78e076)[0x7f5298c14076]
/usr/libexec/mysqld(+0x78e67b)[0x7f5298c1467b]
/usr/libexec/mysqld(+0x79c196)[0x7f5298c22196]
/usr/libexec/mysqld(+0x71bbf1)[0x7f5298ba1bf1]
/usr/libexec/mysqld(+0x71c28f)[0x7f5298ba228f]
/usr/libexec/mysqld(+0x71c8b4)[0x7f5298ba28b4]
/usr/libexec/mysqld(+0x704780)[0x7f5298b8a780]
/usr/libexec/mysqld(+0x72a93f)[0x7f5298bb093f]
/usr/libexec/mysqld(+0x694c17)[0x7f5298b1ac17]
/usr/libexec/mysqld(_Z17mysql_alter_tableP3THDPcS1_P14HA_CREATE_INFOP10TABLE_LISTP10Alter_infojP8st_orderb+0x2990)[0x7f52988e3b40]
/usr/libexec/mysqld(_ZN19Sql_cmd_alter_table7executeEP3THD+0x50e)[0x7f5298926dfe]
/usr/libexec/mysqld(_Z21mysql_execute_commandP3THD+0x865)[0x7f529885a845]
/usr/libexec/mysqld(_Z11mysql_parseP3THDPcjP12Parser_state+0x20b)[0x7f529886173b]
/usr/libexec/mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0x17dc)[0x7f529886356c]
/usr/libexec/mysqld(_Z24do_handle_one_connectionP3THD+0x1e2)[0x7f52989241c2]
/usr/libexec/mysqld(handle_one_connection+0x40)[0x7f5298924260]
/lib64/libpthread.so.0(+0x758a)[0x7f529804a58a]
/lib64/libc.so.6(clone+0x6d)[0x7f5296652e2d]

Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0x7f5230004cd0): ALTER TABLE paymenttransactions     ADD COLUMN p_debtcollectableamount DECIMAL(30,8) AFTER p_refund
Connection ID (thread ID): 25
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_to_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
140618 13:07:26 mysqld_safe Number of processes running now: 0
140618 13:07:26 mysqld_safe mysqld restarted