USB detach/attach hangs with 7.0-RELEASE and 7.1-PRERELEASE

Bruce M Simpson bms at
Mon Sep 29 00:46:17 UTC 2008


I've noticed some general instability with plugging in or removing USB 
devices with FreeBSD 7.x, even when the devices are not actively in use.

I had this happen with umass and ucom devices 3 times today. The machine 
hangs solid, there are no obvious signs of a panic or trap to DDB. I 
can't provide backtraces unfortunately -- these hangs happen on both my 
laptop and desktop, and I usually have X running -- if I had more 
specific information, I'd open a PR.

Again, there seems to be no reason why this should happen, the devices 
are off-the-shelf consumer items known to work with existing drivers, 
and have been repeatedly used in other OSes without these hangs 
happening; consider this an "anecdotal report".

[For some reason my IBM laptop will often not allow me to break into DDB 
on a driver related panic, and will just immediately reboot -- I lack 
free time to track down exactly why this could be.
My desktop has a USB keyboard and this appears not to be supported by 
DDB, I ordered a PS/2 keyboard which hasn't arrived, but that's another 


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