umass panic

[Matthew Dillon]

:on HEAD.
:mounting a USB drive, detaching the drive, then unmounting it 
:panics the system
:...
:umass0: Myson Century, Inc. USB Mass Storage Device, rev 2.00/b0.07, addr 2
:da0 at umass-sim0 bus 0 target 0 lun 0
:da0: <ST94811A  3.05> Fixed Direct Access SCSI-0 device 
:da0: 1.000MB/s transfers
:da0: 38154MB (78140160 512 byte sectors: 255H 63S/T 4864C)
:...
:
:Fatal trap 12: page fault while in kernel mode
:fault virtual address = 0xc
:fault code               = supervisor read, page not present
:instruction pointer    = 0x8:0xc01476e6
:stack pointer           = 0x10:0xcafae8ec
:frame pointer          = 0x10:0xcafae8fc
:code segment        = base 0x0, limit 0xfffff, type 0x1b
:                            = DPL 0, pres 1, def32 1, gran 1
:processor eflags    = interrupt enabled, resume, IOPL = 0
:current process     = 751 (umount)
:current thread       = pri 70 (CRIT)
:
:kernel: type 12 trap, code=0
:
:--ed 
:Eduardo Tongson

    I wouldn't expect good things to happen detaching a drive without
    unmounting it first.  I can reproduce a similar crash and I will fix
    that, but without a DDB backtrace I don't know if what I am 
    reproducing is the same bug you are seeing.  In anycase, look for a
    commit from me tonight and see if it fixes your problem.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>