serious issue caused by usb device, stalling almost all operations

[Alexander Motin]

Hans Petter Selasky wrote:
> On Wednesday 20 October 2010 17:30:40 Alexander Best wrote:
>> hi there,
>>
>> i'm running HEAD (r213495; amd64). i stumbled upon this severe problem:
>>
>> after attaching my mobile phone, it simply resets without doing mount or
>> anything. however after letting the device come up again it won't show up
>> in the console. after detaching it the usb subsystem seemed to have
>> completely crashed. but that's not all. the following programs now simply
>> hang without producing any output C-C won't do anything:
>>
>> - dmesg
>> - top
>> - ps
>> - killall
>> - camcontrol devlist
>> - usbconfig
> 
> That's most likely because USB's umass driver is waiting for cam to drain. 
> Possibly some refcounting is not correct. I suspect this is not a USB problem. 
> Try to enter into the debugger, and look for backtrace for function stuck in 
> umass_detach.

It is a bit suspicious that problem happens only when device dies during
request. Are you sure that running command was properly aborted when
device got detached? Every running command has own set of references,
denying detach.

-- 
Alexander Motin