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

[Tejun Heo <htejun@gmail.com>]

 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.

--
tejun

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