PROBLEM: (94913) (PATCH ID: OSF540-179)
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This patch fixes a bug in usb_hid.mod that only occurs on some error cases.
If the USB HID device (e.g. keyboard or mouse) is not working well, or there
is a signal glitch, this KMF can occur.
It usually happens on boot, or when a HID device has just been connected.  
The typical fault footprint taken from a victim system's boot messages follows:
...
usb0 at pci2 slot 3
usb1 at pci2 slot 103 (slot 3, function 1)
usb2 at pci2 slot 203 (slot 3, function 2)
usb3 at pci2 slot 303 (slot 3, function 3)
pci3 (primary bus:3) at mvioa0 slot 3

trap: invalid memory read access from kernel mode

    faulting virtual address:     0x0000000000000004
    pc of faulting instruction:   0xffffffff0059391c
    ra contents at time of fault: 0xffffffff00593914
    sp contents at time of fault: 0xfffffe067a1cf7d0

panic (cpu 1): kernel memory fault

Here is the stack trace: 

crash> tf
>  0 stop_secondary_cpu   src/kernel/arch/alpha/cpu.c : 1394
   1 panic                src/kernel/bsd/subr_prf.c : 1321
   2 event_timeout        src/kernel/arch/alpha/cpu.c : 2341
   3 printf               src/kernel/bsd/subr_prf.c : 1004
   4 panic                src/kernel/bsd/subr_prf.c : 1378
   5 trap                 src/kernel/arch/alpha/trap.c : 2285
   6 _XentMM              src/kernel/arch/alpha/locore.s : 2219
   7 hid_get_desc         src/kernel/io/dec/usb/usb_hid.c : 999
   8 hid_configure_device  src/kernel/io/dec/usb/usb_hid.c : 282
   9 hub_load_device_driver  src/kernel/io/dec/usb/usb_hub.c : 1525
  10 hub_configure_device  src/kernel/io/dec/usb/usb_hub.c : 1398
  11 hub_read_strings     src/kernel/io/dec/usb/usb_hub.c : 1105
  12 hub_read_device_desc2  src/kernel/io/dec/usb/usb_hub.c : 985
  13 hub_thread           src/kernel/io/dec/usb/usb_hub.c : 4634