Messages in this thread | | | Date | Thu, 13 Mar 2003 09:55:02 +1000 | From | Douglas Gilbert <> | Subject | Re: Problem with aacraid driver in 2.5.63-bk-latest |
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Alan Cox wrote: > On Wed, 2003-03-12 at 23:06, Mark Haverkamp wrote: > >>During probe, scsi_alloc_sdev is called. It calls >>scsi_adjust_queue_depth with the cmd_per_lun value. >>scsi_adjust_queue_depth returns without doing anything if the tags value >>is greater than 256. This leaves the Scsi_Device queue_depth at zero. >>Later when an I/O is queued, scsi_request_fn checks for device_busy >= >>queue_depth. If so, the function does a break and exits. This is where >>it hangs. >> >>To get things to load I set cmd_per_lun to 256. I don't know if the is >>the correct way to deal with the problem. Maybe someone else can say >>something about that. > > > If the SCSI layer is trying to be clever by ignoring the requested 512 > then thats the actual problem. 512 is the right value because its not > really a disk you are talking to on the main channel. So the scsi layer > ought to honour it.
Here is the relevant code snippet in scsi.c around line 930:
void scsi_adjust_queue_depth(Scsi_Device *SDpnt, int tagged, int tags) { static spinlock_t device_request_lock = SPIN_LOCK_UNLOCKED; unsigned long flags;
/* * refuse to set tagged depth to an unworkable size */ if(tags <= 0) return; /* * Limit max queue depth on a single lun to 256 for now. Remember, * we allocate a struct scsi_command for each of these and keep it * around forever. Too deep of a depth just wastes memory. */ if(tags > 256) return; ....
[pardon the wrap] Now scsi_device::queue_depth is an unsigned short so that is not a problem. Also the comment prior to the "if (tags > 256)" is no longer correct (I think). So perhaps it can be changed to "if (tags > 65535) ..."
Doug Gilbert
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