Soft deadlocks

I'm trying to understand what a soft deadlock is as described by deadlock.c.

As best I understand if a process, A, is waiting for a lock and is being
blocked only because someone, B, is ahead of it in the queue but hasn't been
granted the conflicting lock we want to jump A ahead of B.

So if i do something like:

process X:
---------
select * from x where i=1 for share;

----------------

process B:
---------
select * from x where i=1 for update;

----------------

process A:
---------
select * from x where i=1 for share;

process A will block, but when the deadlock timeout fires it should get jumped
ahead of process B.

If that's right then, uh, it doesn't seem to be working.

Process B:

postgres=# select * from x where i = 0 for update;
LOG: process 4629 still waiting for ShareLock on transaction 7802 after 5000.149 ms

Process A:

postgres=# select * from x where i = 0 for share;
LOG: process 4631 still waiting for ShareLock on tuple (0,1) of relation 16423 of database 11408 after 5000.151 ms

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com