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

Tejun Heo
2005-03-23T04:51:15Z

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