Assertion `t->s->tmp_table || thd->mdl_context.owns_equal_or_stronger_lock( MDL_key::TABLE, t->s->db.str , t->s->table_name.str, t->reginfo.lock_type >= TL_WRITE_ALLOW_WRITE ? MDL_SHARED_WRITE : MDL_SHARED_READ)' failed

#0  __pthread_kill (threadid=<optimized out>, signo=6) at ../sysdeps/unix/sysv/linux/pthread_kill.c:62
62      ../sysdeps/unix/sysv/linux/pthread_kill.c: No such file or directory.
[Current thread is 1 (Thread 0x7f6f6d07a700 (LWP 12886))]
(gdb) bt
+bt
#0  __pthread_kill (threadid=<optimized out>, signo=6) at ../sysdeps/unix/sysv/linux/pthread_kill.c:62
#1  0x000000000475d0a3 in my_write_core (sig=6) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/mysys/stacktrace.cc:278
#2  0x000000000359acc4 in handle_fatal_signal (sig=6) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/signal_handler.cc:264
#3  <signal handler called>
#4  0x00007f6f8ad43428 in __GI_raise ([email protected]=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#5  0x00007f6f8ad4502a in __GI_abort () at abort.c:89
#6  0x00007f6f8ad3bbd7 in __assert_fail_base (fmt=<optimized out>, [email protected]=0x5aae8f8 "t->s->tmp_table || thd->mdl_context.owns_equal_or_stronger_lock( MDL_key::TABLE, t->s->db.str, t->s->table_name.str, t->reginfo.lock_type >= TL_WRITE_ALLOW_WRITE ? MDL_SHARED_WRITE : MDL_SHARED_READ)", [email protected]=0x5aae860 "/mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/lock.cc", [email protected]=206, [email protected]=0x5aaf1a0 <lock_tables_check(THD*, TABLE**, unsigned long, unsigned int)::__PRETTY_FUNCTION__> "int lock_tables_check(THD*, TABLE**, size_t, uint)") at assert.c:92
#7  0x00007f6f8ad3bc82 in __GI___assert_fail (assertion=0x5aae8f8 "t->s->tmp_table || thd->mdl_context.owns_equal_or_stronger_lock( MDL_key::TABLE, t->s->db.str, t->s->table_name.str, t->reginfo.lock_type >= TL_WRITE_ALLOW_WRITE ? MDL_SHARED_WRITE : MDL_SHARED_READ)", file=0x5aae860 "/mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/lock.cc", line=206, function=0x5aaf1a0 <lock_tables_check(THD*, TABLE**, unsigned long, unsigned int)::__PRETTY_FUNCTION__> "int lock_tables_check(THD*, TABLE**, size_t, uint)") at assert.c:101
#8  0x000000000378d7ce in lock_tables_check (thd=0x7f6f229f9000, tables=0x7f6f22a17f38, count=10, flags=2048) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/lock.cc:201
#9  0x000000000378daf1 in mysql_lock_tables (thd=0x7f6f229f9000, tables=0x7f6f22a17f38, count=10, flags=2048) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/lock.cc:330
#10 0x00000000032e2bc1 in lock_tables (thd=0x7f6f229f9000, tables=0x7f6f6d0695b0, count=10, flags=2048) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_base.cc:6858
#11 0x00000000032e21a6 in open_and_lock_tables (thd=0x7f6f229f9000, tables=0x7f6f6d0695b0, flags=2048, prelocking_strategy=0x7f6f6d068320) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_base.cc:6593
#12 0x00000000031d82ed in open_and_lock_tables (thd=0x7f6f229f9000, tables=0x7f6f6d0695b0, flags=2048) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_base.h:469
#13 0x00000000036c9dbb in open_grant_tables (thd=0x7f6f229f9000, tables=0x7f6f6d0695b0, transactional_tables=0x7f6f6d069407, db=0x5a89b41 "mysql", table=0x0) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/auth/sql_user_table.cc:1806
#14 0x00000000036d2c6b in mysql_drop_user (thd=0x7f6f229f9000, list=..., if_exists=true) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/auth/sql_user.cc:2126
#15 0x00000000033b6171 in mysql_execute_command (thd=0x7f6f229f9000, first_level=true) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:4387
#16 0x00000000033bc297 in mysql_parse (thd=0x7f6f229f9000, parser_state=0x7f6f6d070340, update_userstat=false, force_primary_storage_engine=false) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:6076
#17 0x00000000033bfd0d in wsrep_mysql_parse (thd=0x7f6f229f9000, rawbuf=0x7f6f22a17028 "DROP USER IF EXISTS 'mysql.pxc.sst.user'@localhost", length=50, parser_state=0x7f6f6d070340, update_userstat=false, force_primary_storage_engine=false) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:7263
#18 0x00000000033ae3c9 in dispatch_command (thd=0x7f6f229f9000, com_data=0x7f6f6d0724c0, command=COM_QUERY) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:2050
#19 0x00000000035a0bb5 in Srv_session::execute_command (this=0x7f6f229f9000, command=COM_QUERY, data=0x7f6f6d0724c0, client_cs=0x7159f20 <my_charset_utf8_general_ci>, callbacks=0x6e99c80 <wsp::Sql_service_context_base::sql_service_callbacks>, text_or_binary=CS_TEXT_REPRESENTATION, callbacks_context=0x7f6f29a06380) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/srv_session.cc:1095
#20 0x00000000035833ca in command_service_run_command (session=0x7f6f229f9000, command=COM_QUERY, data=0x7f6f6d0724c0, client_cs=0x7159f20 <my_charset_utf8_general_ci>, callbacks=0x6e99c80 <wsp::Sql_service_context_base::sql_service_callbacks>, text_or_binary=CS_TEXT_REPRESENTATION, service_callbacks_ctx=0x7f6f29a06380) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/command_service.cc:84
#21 0x00000000035cc268 in server_session_execute (session=0x7f6f229f9000, query="DROP USER IF EXISTS 'mysql.pxc.sst.user'@localhost;", safe_query=0x0) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/wsrep_sst.cc:1129
#22 0x00000000035cc981 in wsrep_remove_sst_user (initialize_thread=false) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/wsrep_sst.cc:1243
#23 0x00000000033b04c6 in shutdown (thd=0x7f6f47024000, level=SHUTDOWN_DEFAULT) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:2584
#24 0x00000000032c67c1 in Sql_cmd_shutdown::execute (this=0x7f6f29b959d8, thd=0x7f6f47024000) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_admin.cc:1745
#25 0x00000000033b9571 in mysql_execute_command (thd=0x7f6f47024000, first_level=true) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:5242
#26 0x00000000033bc297 in mysql_parse (thd=0x7f6f47024000, parser_state=0x7f6f6d076c80, update_userstat=false, force_primary_storage_engine=false) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:6076
#27 0x00000000033bfd0d in wsrep_mysql_parse (thd=0x7f6f47024000, rawbuf=0x7f6f29b95028 "shutdown", length=8, parser_state=0x7f6f6d076c80, update_userstat=false, force_primary_storage_engine=false) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:7263
#28 0x00000000033ae3c9 in dispatch_command (thd=0x7f6f47024000, com_data=0x7f6f6d078c50, command=COM_QUERY) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:2050
#29 0x00000000033abb85 in do_command (thd=0x7f6f47024000) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/sql_parse.cc:1419
#30 0x000000000358428f in handle_connection (arg=0x7f6f763e9160) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/sql/conn_handler/connection_handler_per_thread.cc:311
#31 0x0000000004853dc6 in pfs_spawn_thread (arg=0x7f6f284a8120) at /mnt/workspace/qa.pxc80.build/BUILD_TYPE/debug/Host/min-xenial-x64/storage/perfschema/pfs.cc:2836
#32 0x00007f6f8ca616ba in start_thread (arg=0x7f6f6d07a700) at pthread_create.c:333
#33 0x00007f6f8ae1541d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109