On Thu, 2021-01-21 at 11:05 +0100, Martin Wilck wrote:
> On Thu, 2021-01-21 at 10:07 +0100, Donald Buczek wrote:
> >
> > Unfortunately, this patch (on top of 6eb045e092ef) did not fix the
> > problem. Same error (""controller is offline: status code
> > 0x6100c"")
Rethinking, this patch couldn't have fixed your problem. I apologize
for the dumb suggestion.
However, I still believe I had a point in that patch, and would like to
ask the experts for an opinion.
Assume no commands in flight (busy == 0), host_blocked == 2, and that
two CPUs enter scsi_host_queue_ready() at the same time. Before
6eb045e092ef, it was impossible that the function returned 1 on either
CPU in this situation.
CPU 1 CPU 2
scsi_host_queue_ready scsi_host_queue_ready
host_busy = 1 host_busy = 2
(busy = 0) (busy = 1)
host_blocked = 1 goto starved
goto out_dec add sdev to starved list
host_busy = 1 host_busy = 0
return 0 return 0
With 6eb045e092ef (and without my patch), the result could be:
CPU 1 CPU 2
scsi_host_queue_ready scsi_host_queue_ready
read scsi_host_busy() = 0 read scsi_host_busy() = 0
host_blocked = 1 host_blocked = 0
goto out_dec remove sdev from starved list
return 0 set SCMD_STATE_INFLIGHT
(host_busy = 1)
return 1
So now, one command can be sent, and the host is unblocked. A very
different outcome than before. Was this intentional?
Thanks
Martin
