Re: [PATCH scsi-misc-2.6 08/08] scsi: fix hot unplug sequence

Jens Axboe
2005-03-23T07:20:01Z

On Wed, Mar 23 2005, Tejun Heo wrote:
> Hi,
>
> James Bottomley wrote:
> >On Wed, 2005-03-23 at 11:14 +0900, Tejun Heo wrote:
> >
> >> When hot-unplugging using scsi_remove_host() function (as usb
> >> does), scsi_forget_host() used to be called before
> >> scsi_host_cancel(). So, the device gets removed first without
> >> request cleanup and scsi_host_cancel() never gets to call
> >> scsi_device_cancel() on the removed devices. This results in
> >> premature completion of hot-unplugging process with active
> >> requests left in queue, eventually leading to hang/offlined
> >> device or oops when the active command times out.
> >>
> >> This patch makes scsi_remove_host() call scsi_host_cancel()
> >> first such that the host is first transited into cancel state
> >> and all requests of all devices are killed, and then, the
> >> devices are removed. This patch fixes the oops in eh after
> >> hot-unplugging bug.
> >
> >
> >This is actually simply reversing this patch:
> >
> >http://marc.theaimsgroup.com/?l=linux-scsi&m=109268755500248
> >
> >And all it does is give us the previous consequences back.
> >
> >The oops isn't in the eh it's in the usb-storage eh routine.
>
> Well, but it's because scsi midlayer calls back into usb-storage eh
> after the detaching process is complete.
>
> >However, the current host code does need fixing, but the fix is to move
> >it over to a proper state model rather than the current bit twiddling we
> >do.
>
> I agree & am working on it. This patch was mainly to verify Jens' oops.

It is not the oops I am getting. When I get a few minutes today, I'll
reproduce with vanilla and post it here.

--
Jens Axboe