Cups 1.1.14 1.1.15 and 1.1.16
often block parallel port after a print job is removed.

The lprm command often leaves parallel port in busy state because of process

parallel:/dev/lp0 288 root testprint.ps 1

is still running.
I am not sure about the other backends, but they seems have the same problem
as parallel.

To reproduce: Print a file to a printer that is out of a paper.
Then, even after a job is removed, the process parallel is still running.

[root@ tty]#lpq -Plp
lp is ready and printing
Rank    Owner   Job     File(s)                         Total Size
active  root    289     testprint.ps                    15360 bytes
[root@ tty]# lprm -Plp 289
[root@ tty]# lpq -Plp
lp is ready
no entries
[root@ tty]# ps axuww|grep parall
root      1263  0.0  0.5  2696  684 ?        S    04:55   0:00 parallel:/dev/lp0
289 root testprint.ps 1 

this process block other printing job accessing parallel port.