plug in cdc-acm modem (SONY-Ericsson k600i)
screen /dev/ttyACM0
unplug

usb 1-1: new full speed USB device using uhci_hcd and address 8
usb 1-1: device descriptor read/64, error -71
usb 1-1: new device found, idVendor=0fce, idProduct=d017
usb 1-1: new device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1: Product: Sony Ericsson K600i
usb 1-1: Manufacturer: Sony Ericsson
usb 1-1: SerialNumber: 356572001130309_0
usb 1-1: configuration #1 chosen from 1 choice
cdc_acm 1-1:1.1: ttyACM0: USB ACM device
cdc_acm 1-1:1.3: ttyACM1: USB ACM device
usbcore: registered new driver cdc_acm
drivers/usb/class/cdc-acm.c: v0.25:USB Abstract Control Model driver for USB modems and ISDN adapters
usb 1-1: USB disconnect, address 8
Unable to handle kernel paging request at virtual address 6b6b6beb
 printing eip:
c0281be4
*pde = 00000000
Oops: 0002 [#1]
last sysfs file: /class/net/eth0/carrier
Modules linked in: cdc_acm cp2101 usbserial autofs4 af_packet xircom_cb xircom_tulip_cb ipv6 snd_pcm_oss snd_mixer_oss snd_seq_midi snd_seq_midi_event snd_seq edd toshiba_acpi button battery ac apparmor aamatch_pcre loop dm_mod usbhid pcmcia firmware_class generic snd_es1968 gameport snd_ac97_codec snd_ac97_bus snd_pcm snd_timer snd_page_alloc snd_mpu401_uart snd_rawmidi snd_seq_device snd soundcore donauboe irda crc_ccitt i2c_piix4 i2c_core uhci_hcd usbcore ide_cd cdrom yenta_socket rsrc_nonstatic pcmcia_core parport_pc lp parport ext3 jbd fan thermal processor piix ide_disk ide_core
CPU:    0
EIP:    0060:[<c0281be4>]    Not tainted VLI
EFLAGS: 00210246   (2.6.16-rc5-git2-2-default #1)
EIP is at mutex_lock+0x1c/0x27
eax: 6b6b6beb   ebx: 6b6b6beb   ecx: 00000000   edx: c5ee2000
esi: c11bb440   edi: c11bb448   ebp: c11bb3bc   esp: c5ee3e60
ds: 007b   es: 007b   ss: 0068
Process screen (pid: 4069, threadinfo=c5ee2000 task=cadb7130)
Stack: <0>c02b3eb6 ca34d508 c0182f6e c0790170 c84e1870 6b6b6b6b ca34d508 c11bb440
       c11bb448 c11bb3bc c020c1e9 00000000 c0790170 ca34d508 00000000 00000000
       00000000 c020c264 cbb919c4 ccb2316f cbb919c4 c7e99c94 ccb242d4 c419adf8
Call Trace:
 [<c0182f6e>] sysfs_hash_and_remove+0x2c/0xf6
 [<c020c1e9>] class_device_del+0xb1/0x124
 [<c020c264>] class_device_unregister+0x8/0x10
 [<ccb2316f>] acm_tty_unregister+0x16/0x5c [cdc_acm]
 [<ccb242d4>] acm_tty_close+0xa0/0xaf [cdc_acm]
 [<c01f3851>] release_dev+0x1af/0x649
 [<c015fad5>] do_select+0x38a/0x3b7
 [<c014ca01>] cache_free_debugcheck+0x18a/0x192
 [<c015fd01>] core_sys_select+0x1ff/0x2a0
 [<c015fd01>] core_sys_select+0x1ff/0x2a0
 [<c01f09b7>] tty_ldisc_deref+0x50/0x5f
 [<c01f3cf2>] tty_release+0x7/0xa
 [<c0150b4a>] __fput+0xb3/0x152
 [<c014e60f>] filp_close+0x4e/0x54
 [<c0102ab9>] syscall_call+0x7/0xb
Code: 0f c1 03 48 79 05 89 d8 5b eb 2b 5b 31 c0 c3 53 ba 54 00 00 00 89 c3 83 ec 04 b8 74 ec 29 c0 e8 d8 2d e9 ff e8 49 f6 ff ff 89 d8 <ff> 08 0f 88 5f 01 00 00 58 5b c3 57 56 53 89 c3 83 ec 0c b8 00