[Patch] Fix oops on rmmod usb-storage

[Hannes Reinecke <hare@suse.de>]

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Hi all,

I managed to (hopefully) fix an kernel Oops on rmmod usb-storage.
The Oops we got was something like:

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

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.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux AG				S390 & zSeries
Maxfeldstraße 5				+49 911 74053 688
90409 Nürnberg				http://www.suse.de

[-- Attachment #2: remove_scsi_host_after_cancel.patch --]
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# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
#   2004/09/29 09:27:51+02:00 hare@lammermuir.suse.de 
#   We really should cancel I/O requests before removing the host.
#   
#   Signed-off-by: Hannes Reinecke <hare@suse.de>
# 
# drivers/scsi/hosts.c
#   2004/09/29 09:27:46+02:00 hare@lammermuir.suse.de +1 -1
#   Change ordering to cancel I/O-request before removing the host.
# 
diff -Nru a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
--- a/drivers/scsi/hosts.c	2004-09-29 09:29:19 +02:00
+++ b/drivers/scsi/hosts.c	2004-09-29 09:29:19 +02:00
@@ -75,8 +75,8 @@
  **/
 void scsi_remove_host(struct Scsi_Host *shost)
 {
-	scsi_forget_host(shost);
 	scsi_host_cancel(shost, 0);
+	scsi_forget_host(shost);
 	scsi_proc_host_rm(shost);
 
 	set_bit(SHOST_DEL, &shost->shost_state);