Server crashes on STOP SLAVE, rpl.rpl_parallel_retry fails in buildbot

rpl.rpl_parallel_retry 'mix,xtradb'      w2 [ fail ]

        Test ended at 2016-10-23 04:22:51

CURRENT_TEST: rpl.rpl_parallel_retry

mysqltest: In included file "./include/stop_slave.inc": 

included from /mnt/buildbot/build/mariadb-10.1.19/mysql-test/suite/rpl/t/rpl_parallel_retry.test at line 377:

At line 82: query 'STOP SLAVE' failed: 2013: Lost connection to MySQL server during query

The result from queries just before the failure was:

161023  4:22:50 [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 https://mariadb.com/kb/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: 10.1.19-MariaDB-debug

key_buffer_size=1048576

read_buffer_size=131072

max_used_connections=7

max_threads=153

thread_count=2

It is possible that mysqld could use up to 

key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 61817 K  bytes of memory

Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0xa65063c0

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 = 0xa726a660 thread_stack 0x48400

2016-10-23  4:22:50 2807312192 [Note] Error reading relay log event: slave SQL thread was killed

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(my_print_stacktrace+0x32)[0x8b2c2d5]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(handle_fatal_signal+0x3b7)[0x84d5c43]

[0xb77b7400]

/lib/i386-linux-gnu/libc.so.6(+0x7b678)[0xb72e0678]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x8b49b06]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(_db_keyword_+0x79)[0x8b4a002]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(my_write+0xf6)[0x8b2a6d6]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x8b078b0]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x8b0a6e7]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(my_b_flush_io_cache+0x25e)[0x8b0afea]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(_Z20flush_relay_log_infoP14Relay_log_info+0x1f4)[0x8213e15]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(_ZN14Relay_log_info9stmt_doneEyP3THDP14rpl_group_info+0x1e4)[0x83bdcb8]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(_ZN9Log_event13do_update_posEP14rpl_group_info+0xb5)[0x85c1515]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(_ZN9Log_event10update_posEP14rpl_group_info+0x1f)[0x821625f]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x820b84e]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(_Z39apply_event_and_update_pos_for_parallelP9Log_eventP3THDP14rpl_group_info+0xdd)[0x820bc22]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x843ae7c]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x843d026]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld(handle_rpl_parallel_thread+0xb06)[0x843de0e]

/mnt/buildbot/build/mariadb-10.1.19/sql/mysqld[0x86a5924]

/lib/i386-linux-gnu/libpthread.so.0(+0x6d4c)[0xb753fd4c]

/lib/i386-linux-gnu/libc.so.6(clone+0x5e)[0xb734face]

Trying to get some variables.

Some pointers may be invalid and cause the dump to abort.

Query (0x0): 

Connection ID (thread ID): 1339

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,orderby_uses_equalities=off