umass causes panic on 7 amd64

[Andriy Gapon]

on 16/04/2008 19:19 Roland Smith said the following:
> On Wed, Apr 16, 2008 at 09:10:23AM -0700, Steve Franks wrote:
>> Fatal trap 12: page fault while in kernel mode
>> cpuid = 0; apic id = 00
>> fault virtual address   = 0x0
>> fault code              = supervisor read instruction, page not present
>> instruction pointer     = 0x8:0x0
>> stack pointer           = 0x10:0xffffffffa0208570
>> frame pointer           = 0x10:0xffffff0001e1ca00
>> code segment            = base 0x0, limit 0xfffff, type 0x1b
>>                         = DPL 0, pres 1, long 1, def32 0, gran 1
>> processor eflags        = interrupt enabled, resume, IOPL = 0
>> current process         = 12 (swi4: clock sio)
> 
> Odd. This doesn't seem to have anything to do with usb. It is in a
> kernel thread that runs the clock and serial port.

It is not as odd if you consider that "clock" is actually softclock that
executes timeouts/callouts and I have no doubts that we do use those in
USB subsystem.

> 
> If you give the 'bt' command (backtrace) here, what does it say?

I think 'bt' should be a default command in kgdb init or at least there
should be a big advice to the users: "if you managed to run kgdb on a
core file, then at the very least execute bt command" :-)

-- 
Andriy Gapon