circular wait not triggering deadlock ?

Running pg10.2, I have a handful of maintenance jobs run in the middle of the
night, which appear to have gotten stuck waiting on each other..

. reindex - loop around pg_repack or psql -c REINDEX $table for those which can't
be repacked)
. vacuum - mostly runs ANALYZE, like on empty parent tables

I believe I've come across something similar before, but hadn't previously
stopped to dig into it.

ts=# SELECT * FROM pg_stat_activity WHERE pid=20488;
-[ RECORD 1 ]----+------------------------------------------------------------------------------------------------------------------------------------------
datid | 16402
datname | ts
pid | 20488
usesysid | 10
usename | postgres
application_name | pg_repack
client_addr |
client_hostname |
client_port | -1
backend_start | 2018-03-07 01:00:15.72433-07
xact_start | 2018-03-07 01:00:15.747619-07
query_start | 2018-03-07 01:00:15.747619-07
state_change | 2018-03-07 01:00:15.74762-07
wait_event_type | Lock
wait_event | virtualxid
state | active
backend_xid |
backend_xmin |
query | CREATE INDEX CONCURRENTLY index_1113966210 ON eric_enodeb_cell_20180304 USING btree (site_id) WITH (fillfactor='100') TABLESPACE oldindex
backend_type | client backend

ts=# SELECT * FROM pg_stat_activity WHERE pid=530;
-[ RECORD 1 ]----+--------------------------------------------------------------------------
datid | 16402
datname | ts
pid | 530
usesysid | 10
usename | postgres
application_name | psql
client_addr |
client_hostname |
client_port | -1
backend_start | 2018-03-07 02:11:59.00832-07
xact_start | 2018-03-07 02:11:59.009855-07
query_start | 2018-03-07 02:11:59.009855-07
state_change | 2018-03-07 02:11:59.009861-07
wait_event_type | Lock
wait_event | relation
state | active
backend_xid |
backend_xmin | 67578467
query | ALTER TABLE eric_enodeb_cell_metrics* ALTER start_time SET STATISTICS 400
backend_type | client backend

ts=# SELECT relation::regclass, granted, * FROM pg_locks WHERE (pid=530 AND NOT granted) OR relation='eric_enodeb_cell_20180304'::regclass; -- virtualxid='16/38159763' OR relation='eric_enodeb_cell_metrics'::regclass ORDER BY 1,2,3;
relation | granted | locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted | fastpath
---------------------------+---------+----------+----------+------------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+--------------------------+---------+----------
eric_enodeb_cell_20180304 | t | relation | 16402 | 1113966172 | | | | | | | | 19/28401734 | 20488 | ShareUpdateExclusiveLock | t | f
eric_enodeb_cell_20180304 | f | relation | 16402 | 1113966172 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | f | f

I see PID 530 has ShareUpdateExclusiveLock on many child tables.
..but NOT on eric_enodeb_cell_20180304 , which #20488 is trying to reindex.

ts=# SELECT granted, relation::regclass, * FROM pg_locks WHERE pid=530 OR relation='eric_enodeb_cell_metrics'::regclass ORDER BY 1, 2, 3;
granted | relation | locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted | fastpath
---------+---------------------------+------------+----------+------------+------+-------+-------------+---------------+---------+-------+----------+--------------------+-------+--------------------------+---------+----------
f | eric_enodeb_cell_metrics | relation | 16402 | 948644697 | | | | | | | | 32/838769 | 18941 | AccessShareLock | f | f
f | eric_enodeb_cell_metrics | relation | 16402 | 948644697 | | | | | | | | 18/38156962 | 16592 | AccessExclusiveLock | f | f
f | eric_enodeb_cell_metrics | relation | 16402 | 948644697 | | | | | | | | 31/1337307 | 22961 | AccessShareLock | f | f
f | eric_enodeb_cell_metrics | relation | 16402 | 948644697 | | | | | | | | 27/1755026 | 17248 | AccessShareLock | f | f
f | eric_enodeb_cell_metrics | relation | 16402 | 948644697 | | | | | | | | 28/1118276 | 28357 | AccessShareLock | f | f
f | eric_enodeb_cell_metrics | relation | 16402 | 948644697 | | | | | | | | 29/830016 | 21846 | AccessExclusiveLock | f | f
f | eric_enodeb_cell_20180304 | relation | 16402 | 1113966172 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | f | f
t | eric_enodeb_cell_201609 | relation | 16402 | 193318232 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_201610 | relation | 16402 | 193318241 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_201611 | relation | 16402 | 206004215 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_201612 | relation | 16402 | 232980573 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_201701 | relation | 16402 | 259721731 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_201702 | relation | 16402 | 291841516 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_20170301 | relation | 16402 | 384321707 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_20170302 | relation | 16402 | 385254657 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
t | eric_enodeb_cell_20170303 | relation | 16402 | 386180686 | | | | | | | | 16/38159763 | 530 | ShareUpdateExclusiveLock | t | f
...

ts=# SELECT granted, relation::regclass, * FROM pg_locks WHERE pid=20488 ORDER BY 1,2,3;
-[ RECORD 1 ]------+--------------------------
granted | f
locktype | virtualxid
virtualxid | 22/4317099
virtualtransaction | 19/28401734
pid | 20488
mode | ShareLock
granted | f
fastpath | f

ts=# SELECT granted, pid, mode, virtualtransaction, virtualxid FROM pg_locks WHERE virtualxid='22/4317099' ORDER BY 1,2,3;
granted | pid | mode | virtualtransaction | virtualxid
---------+-------+---------------+--------------------+------------
f | 20488 | ShareLock | 19/28401734 | 22/4317099
t | 6471 | ExclusiveLock | 22/4317099 | 22/4317099

[pryzbyj(at)database ~]$ ps -O lstart -C reindex,pg_repack
PID STARTED S TTY TIME COMMAND
20038 Wed Mar 7 01:00:00 2018 S ? 00:00:00 /bin/sh /usr/local/sbin/reindex
20484 Wed Mar 7 01:00:14 2018 S ? 00:00:00 /bin/sh /usr/local/sbin/reindex
20485 Wed Mar 7 01:00:14 2018 S ? 00:00:00 /usr/pgsql-10/bin/pg_repack -E warning --no-kill-backend -d ts -i eric_enodeb_cell_20180304_site_idx -Ss oldindex

Note, I believe last night our backup job would've run for longer and processed
(many) more tables than usual, looping around pg_dump --snapshot.

Is it a bug that this isn't caught by a deadlock detector and cancelled?

Thanks,
Justin