Re: Overlapped command error handling

[Hannes Reinecke <hare@suse.de>]

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James Bottomley wrote:
> On Thu, 2006-02-02 at 14:00 +0100, Hannes Reinecke wrote:
>> It looks to me as if the device has aborted _both_ commands when
>> returning the 'overlapped commands attempted' sense.
>> Is that conformant behaviour?
>>
>> SCSI-2 states in section 7.5.2:
>> A target that detects an incorrect initiator connection shall abort all
>> I/O processes for the initiator on the logical unit or target routine
>> and shall return CHECK CONDITION status. The sense key shall be set to
>> ABORTED COMMAND and the additional sense code shall be set to OVERLAPPED
>> COMMANDS ATTEMPTED.
> 
> Actually, I think it's probably complaining about tag reuse in the sense
> of SAM-3 section 5.9.3.  You return this sense if an initiator attempts
> to use a duplicate tag.  Since the aic79xx manges its own tags, then
> it's probably a driver error.  You could verify this by having the
> aic79xx print out the tag as it sends the command out on the wire.  (The
> device does support TCQ, doesn't it?)
> 
Argl. Been bitten by the classical 'I know better than thou' attitude.

drivers/scsi/aic7xx/aic79xx_osm.c:ahd_platform_set_tags()
	default:
		/*
		 * We allow the OS to queue 2 untagged transactions to
		 * us at any time even though we can only execute them
		 * serially on the controller/device.  This should
		 * remove some latency.
		 */

but as we also removed the aic7xxx internal timeout handling this means
that the queue_depth is always '2', hence the midlayer might attempt to
send two command simultaneously to the device.
Which is what it did in my case. And, surprisingly enough, setting the
queue depth for the non-TCQ case to '1' fixed the issue.

Can someone explain to my how having a queue depth of '2' in the non-TCQ
case can be correct?
If not, please apply the following patch. Oh, and aic7xxx suffers from
the same problem, naturally.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke			hare@suse.de
SuSE Linux Products GmbH		S390 & zSeries
Maxfeldstraße 5				+49 911 74053 688
90409 Nürnberg				http://www.suse.de

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diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.c b/drivers/scsi/aic7xxx/aic79xx_osm.c
index 78c8338..b9e3776 100644
--- a/drivers/scsi/aic7xxx/aic79xx_osm.c
+++ b/drivers/scsi/aic7xxx/aic79xx_osm.c
@@ -1346,25 +1346,15 @@ ahd_platform_set_tags(struct ahd_softc *
 
 	switch ((dev->flags & (AHD_DEV_Q_BASIC|AHD_DEV_Q_TAGGED))) {
 	case AHD_DEV_Q_BASIC:
-		scsi_adjust_queue_depth(sdev,
-					MSG_SIMPLE_TASK,
-					dev->openings + dev->active);
+		scsi_set_tag_type(sdev, MSG_SIMPLE_TASK);
+		scsi_activate_tcq(sdev, dev->openings + dev->active);
 		break;
 	case AHD_DEV_Q_TAGGED:
-		scsi_adjust_queue_depth(sdev,
-					MSG_ORDERED_TASK,
-					dev->openings + dev->active);
+		scsi_set_tag_type(sdev, MSG_ORDERED_TASK);
+		scsi_activate_tcq(sdev, dev->openings + dev->active);
 		break;
 	default:
-		/*
-		 * We allow the OS to queue 2 untagged transactions to
-		 * us at any time even though we can only execute them
-		 * serially on the controller/device.  This should
-		 * remove some latency.
-		 */
-		scsi_adjust_queue_depth(sdev,
-					/*NON-TAGGED*/0,
-					/*queue depth*/2);
+		scsi_deactivate_tcq(sdev, 1);
 		break;
 	}
 }