[4031] in linux-scsi channel archive
Re: SCSI Timeout on AIC7xxx when PPA is active.
daemon@ATHENA.MIT.EDU (David Campbell)
Fri May 29 01:47:20 1998
From: "David Campbell" <campbell@gear.torque.net>
To: Mark Garlanger <garlangr@cyberramp.net>
Date: Fri, 29 May 1998 13:44:00 +0000
CC: linux-scsi@vger.rutgers.edu
In-reply-to: <356E0C8B.E8B845CA@cyberramp.net>
> From: Mark Garlanger <garlangr@cyberramp.net>
> To: David Campbell <campbell@gear.torque.net>
> > *light bulb over head*
> >
> > The problem may reside in the the AIC7xxx driver. When *any* low level
> > driver completes a command then the mid-level driver checks *all* low
> > level drivers to see if they can accept another command.
> >
> > Perhaps when ppa returns from a command it sees that the AIC7xxx is free
> > (incorrectly) and sends it a SCSI command which jams the queue (this
> > would fit the symptoms).
> >
> > Another posibility is that ppa calls the completion function in an
> > interrupt (OK - software interrupt. tq_timer to be exact). The AIC7xxx may
> > receive its next instruction in this state and do something strange with
> > it.
>
> Would it be possible to move this function completion call to outside the
> interruptin order to test this out.
If I knew a way I would of done it by now. The problem is like this:
ppa enters software interrupt
ppa calls SCSI completion function
SCSI completition function starts queuing commands
AIC7xxx driver recieves request (aic7xxx_queue() is called)
*perhaps breaks here*
My only comment about the AIC7xxx driver (my opinion only) is that the
aic7xxx_queue() function is a little complex. I have spotted a few
kmalloc() in the chain of functions. I am not sure if kmalloc is a valid
function to call in the middle of interrupts - this should be done at init
time (allocate and hold the memory for the life of the driver).
My next question (for the linux-scsi group) is there any other known
conflicts between aic7xxx driver and other SCSI interfaces? OR what other
problems between ppa (Parallel ZIP drive) and other SCSI devices?
Basically I am trying to determine if the problem is aic7xxx or ppa
related.
David Campbell
=======================================================
campbell@torque.net
"All parallel ports are equal - Some are more equal than others"
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