(rr) bt

#0  0x0000000070000002 in ?? ()

#1  0x00007f4fce94c473 in _raw_syscall () at src/preload/raw_syscall.S:120

#2  0x00007f4fce94a477 in traced_raw_syscall (call=0x7f4f9cdfafa0) at src/preload/syscallbuf.c:274

#3  syscall_hook_internal (call=0x7f4f9cdfafa0) at src/preload/syscallbuf.c:3330

#4  syscall_hook (call=0x7f4f9cdfafa0) at src/preload/syscallbuf.c:3364

#5  0x00007f4fce947330 in _syscall_hook_trampoline () at src/preload/syscall_hook.S:313

#6  0x00007f4fce94738f in __morestack () at src/preload/syscall_hook.S:458

#7  0x00007f4fce947396 in _syscall_hook_trampoline_48_3d_01_f0_ff_ff () at src/preload/syscall_hook.S:472

#8  0x00007f4fcdf21201 in kill () from /usr/lib/libc.so.6

#9  0x0000555c5d145f23 in handle_fatal_signal (sig=6) at sql/signal_handler.cc:367

#10 <signal handler called>

#11 0x0000555c5d9d8f4f in my_timer_cycles () at mysys/my_rdtsc.c:170

#12 0x0000555c5d94fc97 in end_mutex_wait_v1 (locker=0x7f4f9d5fad00, rc=0) at storage/perfschema/pfs.cc:3488

#13 0x0000555c5d3a2de3 in PolicyMutex<TTASEventMutex<GenericPolicy> >::pfs_end (this=0x555c5e2a5658 <srv_sys+152>, locker=0x7f4f9d5fad00, ret=0) at storage/innobase/include/ib0mutex.h:738

#14 0x0000555c5d3a0e61 in PolicyMutex<TTASEventMutex<GenericPolicy> >::enter (this=0x555c5e2a5658 <srv_sys+152>, n_spins=30, n_delay=4, name=0x555c5dcf91a8 "storage/innobase/srv/srv0srv.cc", line=944) at storage/innobase/include/ib0mutex.h:596

#15 0x0000555c5d591b28 in srv_release_threads (type=SRV_WORKER, n=3) at storage/innobase/srv/srv0srv.cc:944

#16 0x0000555c5d5963c7 in srv_purge_coordinator_thread (arg=0x0) at storage/innobase/srv/srv0srv.cc:2797

#17 0x00007f4fce90a299 in start_thread () from /usr/lib/libpthread.so.0

#18 0x00007f4fcdfe3053 in clone () from /usr/lib/libc.so.6

  /*

    Force remaining threads to die by closing the connection to the client

    This will ensure that threads that are waiting for a command from the

    client on a blocking read call are aborted.

  */

  for (;;)

  {

    mysql_mutex_lock(&LOCK_thread_count); // For unlink from list

    if (!(tmp=threads.get()))

    {

      mysql_mutex_unlock(&LOCK_thread_count);

      break;

    }

  inline struct ilink *get()

  {

    struct ilink *first_link=first;

    if (first_link == &last)

      return 0;

    first_link->unlink();			// Unlink from list

    return first_link;

  }

  inline void unlink()

  {

    /* Extra tests because element doesn't have to be linked */

    if (prev) *prev= next;

    if (next) next->prev=prev;

    prev=0 ; next=0;

  }

  THD_CHECK_SENTRY(thd);

  unlink_not_visible_thd(thd);

  delete thd;

inline void unlink_not_visible_thd(THD *thd)

{

  thd->assert_linked();

  mysql_mutex_lock(&LOCK_thread_count);

  thd->unlink();

  mysql_mutex_unlock(&LOCK_thread_count);

}

  inline void assert_linked()

  {

    DBUG_ASSERT(prev != 0 && next != 0);

  }

  thd->unlink();