Re: Block timeouts seem not to be working

[Mike Christie <michaelc@cs.wisc.edu>]

James Bottomley wrote:
> On Thu, 2008-09-11 at 20:35 +0200, Jens Axboe wrote:
>> On Thu, Sep 11 2008, James Bottomley wrote:
>>> I just noticed this with a rather finickey SAS system I have.  It's got
>>> a SATA DVD attached over an expander.  Periodically the DVD just hangs
>>> up, so we wait for the timeout and then send a phy reset which clears
>>> it.
>>>
>>> What I'm seeing with the new block timer code is that the timer never
>>> expires.  I can dig some more into this, but if you wanted to test it as
>>> well, the timer code is easy to excite.  Just throw away one command in
>>> every 128 or so in the queuecommand routine of your favourite HBA
>>> driver.
>> James, I've seen a few oddities as well, I'll be beating on it tomorrow
>> again to shake out the last bug(s).
> 
> Actually, turns out it's nothing to do with block timeouts, it's a
> target reset bug.
> 
> This loop:
> 
> 	for (id = 0; id <= shost->max_id; id++) {
> 
> Never terminates if shost->max_id is set to ~0, like aic94xx does.
> 
> It's also pretty inefficient since you mostly have compact target
> numbers, but the max_id can be very high.  The best way would be to sort
> the recovery list by target id and skip them if they're equal, but even
> a worst case O(N^2) traversal is probably OK here.
> 

Sorry about that. I really screwed up on multiple counts there. I tested 
your patch with Linus's tree here on some drivers by setting the command 
timeout to 1 second and letting IO run against slow targets. I saw the 
eh run multiple times and it ran fine with your patch. Thanks for 
finding that.