MySQL Thread Running "SELECT SLEEP(10)" via callgrind

callgrind-with-mysql.txt

# Ran with valgrind --tool=callgrind mysqld ...
# mysql -e 'select sleep(10)'
# callgrind_control -b

  Frame: Backtrace for Thread 24
   [ 0]  pthread_cond_timedwait@@GLIBC_2.3.2 (1 x)
   [ 1]  Interruptible_wait::wait(st_mysql_cond*, st_mysql_mutex*) (1 x)
   [ 2]  Item_func_sleep::val_int() (1 x)
   [ 3]  Item::send(Protocol*, String*) (2 x)
   [ 4]  Protocol::send_result_set_row(List<Item>*) (2 x)
   [ 5]  select_send::send_data(List<Item>&) (2 x)
   [ 6]  JOIN::exec() (2 x)
   [ 7]  mysql_select(THD*, TABLE_LIST*, unsigned int, List<Item>&, Item*, SQL_I_List<st_order>*, SQL_I_List<st_order>*, Item*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*) (2 x)
   [ 8]  handle_select(THD*, select_result*, unsigned long) (2 x)
   [ 9]  execute_sqlcom_select(THD*, TABLE_LIST*) (2 x)
   [10]  mysql_execute_command(THD*) (2 x)
   [11]  mysql_parse(THD*, char*, unsigned int, Parser_state*) (2 x)
   [12]  dispatch_command(enum_server_command, THD*, char*, unsigned int) (2 x)
   [13]  do_command(THD*) (2 x)
   [14]  do_handle_one_connection(THD*) (1 x)
   [15]  handle_one_connection (1 x)
   [16]  pfs_spawn_thread (2 x)
   [17]  start_thread (23 x)
   [18]  clone
   
# mysqld shutting down

  Frame: Backtrace for Thread 25
   [ 0]  os_event_free(os_event*) (4499836 x)
   [ 1]  os_sync_free() (1 x)
   [ 2]  innobase_shutdown_for_mysql() (1 x)
   [ 3]  innobase_end(handlerton*, ha_panic_function) (1 x)
   [ 4]  ha_finalize_handlerton(st_plugin_int*) (5 x)
   [ 5]  reap_plugins() (2 x)
   [ 6]  plugin_shutdown() (1 x)
   [ 7]  clean_up(bool) [clone .part.183] (1 x)
   [ 8]  unireg_end() (1 x)
   [ 9]  kill_server(void*) [clone .constprop.217] (1 x)
   [10]  kill_server_thread (1 x)
   [11]  pfs_spawn_thread (1 x)
   [12]  start_thread (1 x)
   [13]  clone