When I have a printer plugged into a USB port,
any attempt to attach an USB stick or hard drive leads to a total system lockup.
By pre-emptively launching “top” in the console on Ctrl+Alt+F1 I managed to get the culprit.
It’s the process named “usb-stor-scan”, gobbling up 100% CPU (both its cores, it seems). The “nice” of this process is -5, which is fatal, as the system quickly (in two or three seconds) stops responding to mouse and keyboard. Then the only way out is a hard reset :’(
I performed several tests, this happens only while the printer is attached (Samsung ML-1750).
The lockup happens with 100% certainity if I attach an USB drive.
The lockup happens with some small probability when I send a print job from one of the Windows machines (the printer is shared using samba) while I have a previously attached USB drive.
I don’t know, maybe this is a consequence of some hardware problem, as the computer is brand new, with quite cheap power supply unit.
The lockup happens with 100% certainity if I attach an USB drive.
Just a guess - I’m wondering if this is a current supply issue. That can cause problems like this. Is the usb HDD powered direct;y from the usb port? Try using an active hub and see if that makes a difference.
You were absolutely right.
Today I changed my power supply unit, from a suspicious noname to a decent one of a good brand. The problem just disappeared.
When I performed an autopsy of the old PSU, I was horrified. It looked it was assembled by a drunk janitor on his shaky knee. Not to mention the air flow completely missing the heatsinks.
People, NEVER use the PSU that comes already installed in the case you buy. Throw it away (or buy a bare case without a PSU) then buy a good PSU separately!
