format.sh: /data/bostic/RUNDIR.4 log:
    t: process 92805 running
    [1588803042:642563][92805:0x7fa3a17b8700], t, file:wt.wt, WT_SESSION.rollback_transaction: __txn_fixup_prepared_update, 722: upd->ne
xt != NULL && upd->next->next == NULL && upd->next->txnid == WT_TXN_ABORTED
    [1588803042:642598][92805:0x7fa3a17b8700], t, file:wt.wt, WT_SESSION.rollback_transaction: __wt_abort, 22: process ID 92805: waiting
 for debugger...

(gdb) where
#0  0x00007fa3a8cf403f in __GI___select (nfds=0, readfds=0x0, writefds=0x0, exceptfds=0x0,
    timeout=0x7fa3a17b7b50) at ../sysdeps/unix/sysv/linux/select.c:41
#1  0x0000555cc247fe11 in __wt_sleep (seconds=100, micro_seconds=0) at src/os_posix/os_sleep.c:30
#2  0x0000555cc24755e1 in __wt_abort (session=0x7fa3a97e9e30) at src/os_common/os_abort.c:26
#3  0x0000555cc24dbc4c in __txn_fixup_prepared_update (session=0x7fa3a97e9e30, op=0x7fa390aa48f0,
    cursor=0x7fa390c32210, commit=false) at src/txn/txn.c:721
#4  0x0000555cc24dc39b in __txn_resolve_prepared_op (session=0x7fa3a97e9e30, op=0x7fa390aa48f0,
    commit=false, cursorp=0x7fa3a17b7d70) at src/txn/txn.c:894
#5  0x0000555cc24ddca9 in __wt_txn_rollback (session=0x7fa3a97e9e30, cfg=0x7fa3a17b7e10)
    at src/txn/txn.c:1531
#6  0x0000555cc24b87d0 in __session_rollback_transaction (wt_session=0x7fa3a97e9e30, config=0x0)
    at src/session/session_api.c:1735
#7  0x0000555cc23dc746 in rollback_transaction (tinfo=0x555cc4a1dc10) at ops.c:485
#8  0x0000555cc23ddd61 in ops (arg=0x555cc4a1dc10) at ops.c:1000
#9  0x00007fa3a8fd56db in start_thread (arg=0x7fa3a17b8700) at pthread_create.c:463
#10 0x00007fa3a8cfe88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95
(gdb) frame 3
#3  0x0000555cc24dbc4c in __txn_fixup_prepared_update (session=0x7fa3a97e9e30, op=0x7fa390aa48f0,
    cursor=0x7fa390c32210, commit=false) at src/txn/txn.c:721
721             WT_ASSERT(session,
(gdb) list 710,730
710              */
711             F_SET(upd, WT_UPDATE_RESTORED_FOR_ROLLBACK);
712             
713             /*
714              * There should be only one aborted prepared update in the list, append it after the new
715              * update.
716              */
717             if (cbt->ins != NULL)
718                 upd->next = cbt->ins->upd;
719             else if (cbt->ref->page->modify != NULL && cbt->ref->page->modify->mod_row_update != NULL)
720                 upd->next = cbt->ref->page->modify->mod_row_update[cbt->slot];
721             WT_ASSERT(session,
722               upd->next != NULL && upd->next->next == NULL && upd->next->txnid == WT_TXN_ABORTED);
723               
724             /* Append a tombstone if the stop timestamp exists. */
725             if (hs_stop_ts != WT_TS_MAX) {
726                 WT_ERR(__wt_upd_alloc(session, NULL, WT_UPDATE_TOMBSTONE, &tombstone, NULL));
727                 tombstone->durable_ts = hs_stop_ts;
728                 tombstone->start_ts = hs_stop_ts;  
729                 tombstone->txnid = WT_TXN_NONE;    
730                 tombstone->next = upd;

(gdb) yyy
$4 = {
  txnid = 0,
  durable_ts = 0,
  start_ts = 0,
  next = 0x7fa3900dc3c0,
  size = 20,
  type = 3 '\003',
  prepare_state = 0 '\000',
  flags = 2 '\002',
  data = 0x7fa390728917 "0000784291/LMNOPQRST"
}
$5 = {
  txnid = 18446744073709551615,
  durable_ts = 0,
  start_ts = 40154,
  next = 0x7fa39018cbd0,
  size = 45,
  type = 3 '\003',
  prepare_state = 1 '\001',
  flags = 0 '\000',
  data = 0x7fa3900dc3e7 "0000784291/LMNOPQRST"
}
$6 = {
  txnid = 18446744073709551615,
  durable_ts = 0,
  start_ts = 0,
  next = 0x0,
  size = 0,
  type = 2 '\002',
  prepare_state = 0 '\000',
  flags = 0 '\000',
  data = 0x7fa39018cbf7 ""
}