mariabackup.xb_rocksdb failed in buildbot, server hung on shutdown

mariabackup.xb_rocksdb                   w3 [ fail ]  Found warnings/errors in server log file!

        Test ended at 2018-08-15 15:33:31

line

Attempting backtrace. You can use the following information to find out

^ Found warnings in /dev/shm/var/3/log/mysqld.1.err

ok

Version: '10.3.10-MariaDB-1:10.3.10+maria~stretch-log'  socket: '/dev/shm/var/tmp/3/mysqld.1.sock'  port: 16060  mariadb.org binary distribution

2018-08-15 15:32:28 0 [Note] /usr/sbin/mysqld (initiated by: root[root] @ localhost []): Normal shutdown

2018-08-15 15:32:28 0 [Note] Event Scheduler: Purging the queue. 0 events

2018-08-15 15:32:28 0 [Note] InnoDB: FTS optimize thread exiting.

2018-08-15 15:32:28 0 [Note] InnoDB: Starting shutdown...

2018-08-15 15:32:28 0 [Note] InnoDB: Dumping buffer pool(s) to /dev/shm/var/3/mysqld.1/data/ib_buffer_pool

2018-08-15 15:32:28 0 [Note] InnoDB: Instance 0, restricted to 127 pages due to innodb_buf_pool_dump_pct=25

2018-08-15 15:32:28 0 [Note] InnoDB: Buffer pool(s) dump completed at 180815 15:32:28

2018-08-15 15:32:29 0 [Note] InnoDB: Shutdown completed; log sequence number 1642517; transaction id 34

2018-08-15 15:32:29 0 [Note] InnoDB: Removed temporary tablespace data file: "ibtmp1"

180815 15:33:28 [ERROR] mysqld got signal 6 ;

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: 10.3.10-MariaDB-1:10.3.10+maria~stretch-log

key_buffer_size=1048576

read_buffer_size=131072

max_used_connections=1

max_threads=153

thread_count=0

It is possible that mysqld could use up to 

key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 63172 K  bytes of memory

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

Thread pointer: 0x0

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 = 0x0 thread_stack 0x49000

Fatal signal 11 while backtracing

/usr/sbin/mysqld(my_print_stacktrace+0x2e)[0x55f8f9068f3e]

/usr/sbin/mysqld(handle_fatal_signal+0x41f)[0x55f8f8b12f2f]

Fatal signal 11 while backtracing

/lib/x86_64-linux-gnu/libpthread.so.0(+0x110c0)[0x7f04c99b10c0]

/lib/x86_64-linux-gnu/libpthread.so.0(pthread_cond_wait+0xbf)[0x7f04c99ad15f]

Fatal signal 11 while backtracing

/usr/sbin/mysqld(_Z11mysqld_mainiPPc+0x1311)[0x55f8f8888631]

Fatal signal 11 while backtracing

/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0x7f04c7e392e1]

Fatal signal 11 while backtracing

/usr/sbin/mysqld(_start+0x2a)[0x55f8f887a75a]

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 at /dev/shm/var/3/mysqld.1/data/