[Pvfs2-developers] state machine ending

[Sam Lang]

On Jul 24, 2006, at 2:07 PM, Pete Wyckoff wrote:

> walt at clemson.edu wrote on Mon, 24 Jul 2006 14:47 -0400:
>> 3) the state machine language has a keyword that lets you state  
>> that the
>> next state is "terminate" which could be used to finish the state
>> machine, but right now the code has logic that detects this and  
>> prints a
>> warning that you should NOT use this.  I don't know why we created  
>> this
>> method and then made it illegal.  Go figure!
>
> I prefer #3 by a large margin over the other options.  It's
> explicit, not racy, doesn't over-use the return value for a
> conceptually different event, and doesn't rely on modifying
> parent state.  Wonder why it was disabled.
>
I think terminate ended up being more of a placeholder...we still use  
it in quite a few of our state machines, but the last state action is  
expected to call server_state_machine_complete which prevents the SM  
from transitioning to the 'terminate' state.  I've thought of it as  
an assert:  if you get here you're forgetting something.

It sounds like option 3 is best.  My only concern would be using the  
state machine definition to define completion makes me forget about  
cleaning up in the last action (or actions).  I wouldn't mind seeing  
option 3 and option 4 being required:  check the return code and make  
sure the next state is 'terminate'.  If one of those fails there's a  
bug in the code.  I think that might help (at least me) verify that  
state actions that are meant to complete need to do cleanup first.

-sam


> Regarding names, STATE_COMPLETE and STATE_MACHINE_TERMINATED seem
> like find candidates as you have sort of suggested.
>
> My pocket change.
>
> 		-- Pete
> _______________________________________________
> Pvfs2-developers mailing list
> Pvfs2-developers at beowulf-underground.org
> http://www.beowulf-underground.org/mailman/listinfo/pvfs2-developers
>