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

[Dmitry Morozovsky]

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 ;)

-- 
Sincerely,
D.Marck                                     [DM5020, MCK-RIPE, DM3-RIPN]
[ FreeBSD committer:                                 marck at FreeBSD.org ]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck at rinet.ru ***
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