On Mon, Mar 11, 2013 at 11:08 AM, Mike Christie <michaelc@xxxxxxxxxxx> wrote: >> If at the same time a SAS fabric event goes to the HBA, what can >> happen is the following: >> >> - mpt2sas calls _scsih_block_io_all_device() -> scsi_internal_device_block(sdev) >> >> (In response to some HBA firmware event like MPI2_EVENT_SAS_BROADCAST_PRIMITIVE) >> Now sdev state is SDEV_BLOCK and blockdev queue has QUEUE_FLAG_STOPPED set. >> >> - Someone like scsi_add_lun() calls scsi_device_set_state(sdev, SDEV_RUNNING) >> >> (SCSI bus scanning runs asynchronously to firmware event handling) >> Now sdev state is SDEV_RUNNING but blockdev queue still has QUEUE_FLAG_STOPPED set > > Is this a valid state change? Should it be failed in > scsi_device_set_state when we try to go from SDEV_BLOCKED -> > SDEV_RUNNING? I am not sure if it make senses to ever have a device in > SDEV_RUNNING but have the stopped queue bit set. > > It used to be that scsi_internal_device_unblock called > scsi_device_set_state so the transition from SDEV_BLOCKED to > SDEV_RUNNUNG had to be a valid transition. scsi_internal_device_unblock > then started the queue. I am not sure if the sequence you were hitting > was actually a transition that was intended or just worked by accident. > > Should we be failing the above call to scsi_device_set_state, and then > the call to scsi_internal_device_unblock would work as expected. Dunno ... I was a bit scared to go too deep into this sdev_state stuff, since it looks very old and fragile. With that said the big question to me is who really owns the state -- is it the low-level driver or the midlayer? I don't quite understand what it means for the midlayer to try and start a device if the low-level driver has temporarily paused things. However since we have the blockdev queue stopped state also, it seems to make things work out OK. - R. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
