Re: [Patch] Fix oops on rmmod usb-storage

[James Bottomley <James.Bottomley@SteelEye.com>]

On Wed, 2004-09-29 at 03:43, Hannes Reinecke wrote:
> usbcore: deregistering driver usb-storage
> scsi: Device offlined - not ready after error recovery: host 0 channel 0 
> id 0 lun 0
> sr 0:0:0:0: Illegal state transition cancel->offline
> Badness in scsi_device_set_state at drivers/scsi/scsi_lib.c:1688
>   [<e12bab6e>] scsi_device_set_state+0x9e/0xd0 [scsi_mod]
>   [<e12b8a6e>] scsi_eh_offline_sdevs+0x4e/0x70 [scsi_mod]
>   [<e12b8f1a>] scsi_unjam_host+0x9a/0x1b0 [scsi_mod]
>   [<e12b90f5>] scsi_error_handler+0xc5/0x160 [scsi_mod]
>   [<e12b9030>] scsi_error_handler+0x0/0x160 [scsi_mod]
>   [<c0104255>] kernel_thread_helper+0x5/0x10

This isn't an oops, it's a state transition warning.  Apparently the
customary attempt to cancel the commands failed.  This is really only a
warning and will probably go away eventually (we'll just silently fail
the transition attempt).

> It turned out that in drivers/scsi/hosts.c:scsi_remove_host()
> first the host is removed with scsi_forget_host() and _then_ all 
> outstanding I/O to this host is cancelled with scsi_host_cancel(). 
> Sounds a bit fishy as scsi_host_cancel() tries to talk to a host which 
> we just have deleted ...
> (Incidentally, this is most likely the same bug as Bug #2752 and #3480 
> from bugme.osdl.org :-).
> (And also #133249 from bugzilla.redhat.com :-).
> 
> The attached patch corrects this.
> Please apply.

No, the patch is wrong.  we do forget first to make the host
inaccessible from above then cancel the outstanding commands.

The key to the solution of this problem is to know what USB is trying to
do with the dead device.  SCSI is trying to be polite and explicitly
kill the outstanding commands before it removes the HBA.  Presumably USB
is returning something that says this can't be done so the EH gets all
the way up to offlining.

Also, please at least cc linux-scsi@vger.kernel.org on SCSI problems.

Thanks,

James