Re: Who owns qlogicisp?

From: Peter Rival (
Date: Tue Jun 20 2000 - 15:32:49 EST

I hate replying to my own mail, but seeing as nobody else is... :)

Peter Rival wrote:

> General thought so far:
> It appears that somehow the scsi command pointed to by Cmnd (as set in
> qlogicisp.c:1031) is NULL at some point in the loop, and we don't ever check
> for that occurrence. My question is, is that a valid state for the command
> slot, and if so, shouldn't we just continue on to the next one? Essentially,
> what we have is this:
> while (out_ptr != in_ptr) {
> u_int cmd_slot;
> sts = (struct Status_Entry *) &hostdata->res_cpu[out_ptr];
> out_ptr = (out_ptr + 1) & RES_QUEUE_LEN);
> cmd_slot = sts_handle;
> Cmnd = hostdata->cmd_slots[cmd_slot];
> <should we check that Cmnd is not null here, and if it is just
> continue?>

If I add just a simple
    if (!Cmnd)
there are no more oopses. However, instead of oopses we now get SCSI command

>From a little more debugging, it appears that somewhere between writing out the
commands (in isp1020_queuecommand()) and taking them off of the cmd_slots array
(in isp1020_intr_handler()) we're moving a pointer to somewhere it doesn't
belong (my current guess is one beyond the end of the queue) and therefore
getting NULL Scsi_Cmnd pointers. I'll keep digging...maybe this knocks some
dust of someone's recollection...

 - Pete

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