svn commit: r254615 - head/sys/dev/mps

[Scott Long]

On Aug 22, 2013, at 7:58 AM, Dmitry Morozovsky <marck at rinet.ru> wrote:

> On Thu, 22 Aug 2013, Kenneth D. Merry wrote:
> 
>>>>  Fix mps(4) driver breakage that came in in change 253550 that
>>>>  manifested itself in out of chain frame conditions.
>>>> 
>>>>  When the driver ran out of chain frames, the request in question
>>>>  would get completed early, and go through mpssas_scsiio_complete().
> 
>>> what is real impact of the bug?
>> 
>> Your system will essentially hang, certainly as far as anything connected
>> to the controller in question.
> 
> [snip]
> 
>> 5.  Look for an out of chain frames message on the console.  To see how far
>> you are towards using the chain frames, run 'sysctl dev.mps'.  You can see
>> how many chain frames you have free, and how many requests have failed.
>> 
>> This change just needs to be merged along with the other changes to avoid
>> having the regression in stable.
> 
> Thank you very much for the explanation.  We use a couple of servers with mps 
> (and many spindles there), all on stable/9 from this summer, and you commit 
> turns on an alarm light in my head ;)


I'll confirm with my netflix hat on that this isn't a problem in 9.

Scott