kern/73744: printing via cups causes "Interrupt storm" warning, throttles output

bob frazier bobf at
Tue Nov 9 13:00:49 PST 2004

>Number:         73744
>Category:       kern
>Synopsis:       printing via cups causes "Interrupt storm" warning, throttles output
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Nov 09 21:00:48 GMT 2004
>Originator:     bob frazier
>Release:        5.3-STABLE #1 (RELENG_5)
FreeBSD BSDServer.SFT.local 5.3-STABLE FreeBSD 5.3-STABLE #1: Tue Oct 26 20:13:16 PDT 2004     root@:/usr/obj/usr/src/sys/GENERIC  i386

following a very recent portupgrade to RELEASE_5_3_0, printing via cups now causes the following error message to appear on the console:

Interrupt storm detected on "irq7:lpt0": throttling interrupt source

This caused printing to be GROSSLY unacceptably slow

stopping cups, then using 'lptcontrol -p /dev/lpt0', then restarting it again worked around the problem and restored acceptable print performance.

This is the first time I have seen this happen, and I have been printing on this machine for quite some time.

a) install FBSD 5.3-STABLE #1, cups, and samba.  lpt0 is set up for IRQ 7 (this may be an automatic setting as I didn't enter anything in 'device.hints' for lpt0).
b) configure for 'RAW' output on /dev/lpt0 (in this case, with an HP DeskJet 660C connected to the port).
c) from a windows machine, print something to the printer via the SAMBA share using the correct windows driver and 'RAW' output.  This may also be possible using the 'print test page' options from the http "printer admin" interface for cups via the cups 'deskjet' driver (for postscript - I did not specifically test this).
d) Observe 'interrupt storm' warning on console
e) observe piss poor printing performance
f) shut down cups, enter command 'lptcontrol -p /dev/lpt0'
g) repeat the printer test, printing resumes normally

disable interrupt-driven printing via 'lptcontrol'


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