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

Ronald Klop ronald-freebsd8 at
Mon Sep 29 20:05:20 UTC 2008

On Mon, 29 Sep 2008 02:46:15 +0200, Bruce M Simpson <bms at>  

> Hi,
> 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  
> story.]
> thanks

On my computer I had to disable USB support in the BIOS because it  
'conflicted' with USB support of FreeBSD.
FreeBSD still detects USB and all connected devices.
Maybe this helps on your computer also.


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