Re: aic79xx driver - hotswap error

[Hannes Reinecke <hare@suse.de>]

Doug Ledford wrote:
> On Mon, 2006-08-28 at 14:15 +0200, Martin Zuziak wrote:
>> Hello all
>>
>> Hot-swapping doesn't seem to work with the aic79xx driver in kernel
>> 2.6.17.9. Removing or adding a disk from/to a running system makes i/o
>> to any disk on the bus fail.
>>
>> The machine is an IBM x346 server with a x86_64 cpu and a aic7902 scsi
>> controller.
>>
>> A copy of the system log is here:
>> http://www.math.ku.dk/~zuziak/tmp/aic79xx_error_2.6.17.9.log
>>
>> It shows the result of removing the third disk: the first disk (the only
>> one mounted) becomes inaccessible.
>>
>> Kernel 2.6.15.7 seems to work but I have had no luck with newer kernels.
>>
>> Has anyone seen hot-swapping work with the aic79xx driver in recent
>> kernels?
> 
> Are you sure your system is hot swap safe?  The whole log mess begins
> with "someone reset channel A" which means the card detected a bus reset
> but it didn't initiate the reset.  That's either going to be because
> your system shouldn't be hot swap plugged and it triggered a spike on
> the reset pin, or because your hot swap drive setup resets the bus on
> unplug intentionally.  Knowing that would help.
> 
> So, the driver managed to get into the ahd_pause_and_flushwork()
> function, probably while trying to queue the abort SCB, and while there
> it detected an infinite loop and printed out the "Infinite interrupt
> loop, INTSTAT = 8" message.  The INTSTAT value of 0x08 maps to SCSIINT,
> so next you would look at the SCSIINT1 and SCSIINT2 registers to see
> just *what* is causing the loop.  There you see SSTAT1[0x20]:(SCSIRSTI).
> This tells us the driver is *still* getting a SCSI Reset In interrupt
> from the card, even over 1 minute after you pulled the drive.  So, the
> reason your SCSI bus hung is because everything on the bus is being
> subjected to an infinite bus reset condition.  The cause of this
> happening is likely either A) your bus isn't hot swap safe and you hot
> swapped anyway, and in the process you disconnected the termination
> power source or termination itself or just plain flaked other devices on
> the bus out or B) something in your hot swap enclosure is broken and
> throws an infinite bus reset when the drive is removed.  Either way,
> this is not what I would call expected behavior from the aic79xx driver,
> I suspect that it is innocent here and that the hardware is to blame.
> 
Thanks Doug.
I couldn't have phrased it better.

Hotswap does work, provided you don't do anything untoward.
Which translates as "might work but don't blame me if it doesn't".
And I would never ever claim that it is a supported feature.

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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