Done Timeout vs. Credit Timeout Race

Day, Brian bday at lsil.com
Thu Mar 6 15:47:54 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Day, Brian" <bday at lsil.com>
*

I believe some folks within LSI have thought of a race condition between the
Done Timeout and the Credit Timout timers 
in the SSP link layers.  Consider the case when a device (device A) has
issued DONE and has not extended credit to the
other device (device B) which still has frames to send.  Device A starts its
1ms Done Timeout timer as soon as it sends
the DONE.  Device B will start its 1ms Credit Timeout timer after a new Tx
Frame request is received.

There's a good chance the Done Timeout will occur first, which results in a
BREAK being transmitted by device A.
When device B receives the BREAK, it filters on up through the layers and
ends up as a DELIVERY FAILURE for the frame
that was attempting to get transmitted.

That's doesn't seem like what was the intent for what was really a credit
timeout.

Am I missing something here?  Thanks....

Brian Day
LSI Logic


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