Running kernel 2.6.27-rc1-00156-g94ad374 on x86-64, I

1) plugged in a USB device

quoted text
> Aug  8 15:32:03 core kernel: usb 1-8: new high speed USB device using ehci_hcd a
> nd address 4
> Aug  8 15:32:04 core kernel: usb 1-8: configuration #1 chosen from 1 choice
> Aug  8 15:32:04 core kernel: usb 1-8: New USB device found, idVendor=041e, idPro
> duct=4155
> Aug  8 15:32:04 core kernel: usb 1-8: New USB device strings: Mfr=1, Product=2, 
> SerialNumber=3
> Aug  8 15:32:04 core kernel: usb 1-8: Product: ZEN Stone Plus
> Aug  8 15:32:04 core kernel: usb 1-8: Manufacturer: CREATIVE
> Aug  8 15:32:04 core kernel: usb 1-8: SerialNumber: F03A09331004CD04
> Aug  8 15:32:04 core kernel: Initializing USB Mass Storage driver...
[...]
quoted text
> scsi 10:0:0:0: Direct-Access     CREATIVE ZEN Stone Plus   1031 PQ: 0 ANSI: 4
> sd 10:0:0:0: [sdc] 963968 2048-byte hardware sectors (1974 MB)
> sd 10:0:0:0: [sdc] Write Protect is off
> sd 10:0:0:0: [sdc] Mode Sense: 38 00 00 00
> sd 10:0:0:0: [sdc] Assuming drive cache: write through


2) I executed: sudo dd if=/dev/sdc of=foo.img bs=32k


3) judging from ls(1), the entire storage device's contents was 
successfully dumped to my hard drive.  HOWEVER, dd(1) sat in disk wait, 
failing to end execution once the end of the USB storage device was reached.


4) a huge amount of dmesg spew followed.  at the time of this writing, 
the following spew has been passed to dmesg over TWO HUNDRED times:

quoted text
> Aug  8 15:41:01 core kernel: INFO: task usb-storage:21894 blocked for more than 
> 120 seconds.
> Aug  8 15:41:01 core kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" 
> disables this message.
> Aug  8 15:41:01 core kernel: usb-storage   D 0000000000000000     0 21894      2
> Aug  8 15:41:01 core kernel: ffff880005b0fc50 0000000000000046 ffff880005b0fc18 
> ffff880005b0fc14
> Aug  8 15:41:01 core kernel: ffffffff805f1000 ffff88005d6f7130 ffffffff80567340 
> ffff88005d6f7378
> Aug  8 15:41:01 core kernel: 0000000005b0fc48 0000000105d90aa2 ffff88005d6f7378 
> 00000000000005fe
> Aug  8 15:41:01 core kernel: Call Trace:
> Aug  8 15:41:01 core kernel: [<ffffffff80495edd>] schedule_timeout+0xad/0xf0
> Aug  8 15:41:01 core kernel: [<ffffffff80495edd>] schedule_timeout+0xad/0xf0
> Aug  8 15:41:01 core kernel: [<ffffffff80495307>] wait_for_common+0xb7/0x170
> Aug  8 15:41:01 core kernel: [<ffffffff80232640>] default_wake_function+0x0/0x10
> Aug  8 15:41:01 core kernel: [<ffffffff803c0ed0>] usb_sg_wait+0x130/0x190
> Aug  8 15:41:01 core kernel: [<ffffffffa02f78f8>] usb_stor_bulk_transfer_sglist+0xa8/0x120 [usb_storage]
> Aug  8 15:41:01 core kernel: [<ffffffffa02f79e6>] usb_stor_bulk_srb+0x26/0x40 [usb_storage]
> Aug  8 15:41:01 core kernel: [<ffffffffa02f7b2c>] usb_stor_Bulk_transport+0x12c/0x2d0 [usb_storage]
> Aug  8 15:41:01 core kernel: [<ffffffffa02f75dc>] usb_stor_invoke_transport+0x3c/0x2b0 [usb_storage]
> Aug  8 15:41:01 core kernel: [<ffffffff80495312>] wait_for_common+0xc2/0x170
> Aug  8 15:41:01 core kernel: [<ffffffff80232640>] default_wake_function+0x0/0x10
> Aug  8 15:41:01 core kernel: [<ffffffffa02f8f4b>] usb_stor_control_thread+0x13b/0x220 [usb_storage]
> Aug  8 15:41:01 core kernel: [<ffffffffa02f8e10>] usb_stor_control_thread+0x0/0x220 [usb_storage]
> Aug  8 15:41:01 core kernel: [<ffffffff8024d867>] kthread+0x47/0x90
> Aug  8 15:41:01 core kernel: [<ffffffff80235247>] schedule_tail+0x27/0x70
> Aug  8 15:41:01 core kernel: [<ffffffff8020c6d9>] child_rip+0xa/0x11
> Aug  8 15:41:01 core kernel: [<ffffffff8024d820>] kthread+0x0/0x90
> Aug  8 15:41:01 core kernel: [<ffffffff8020c6cf>] child_rip+0x0/0x11
> Aug  8 15:41:01 core kernel:


5) Losing patience, I unplugged the USB device.  dmesg spew continues.


6) Losing more patience, I 'kill -9' the dd(1) process.  dmesg spew 
continues.


It is completely silly to fill my dmesg buffer many times over, with the 
same basic information.  /proc/sys/kernel/hung_task_timeout_secs is 
completely irrelevant here, you need spew limiting in addition to fixing 
the USB storage hang problem.


Unfortunately, the USB device was not mine, so it is already hundreds of 
miles away from me.  I can provide plenty of information about my 
current machine state and config though, just ask.  lspci and config 
attached.

Huge /var/log/messages with all dmesg spew available upon request; I 
didn't want to post the whole thing.

	Jeff