[Pvfs2-developers] terminating state machines

[Walter B. Ligon III]

OK, guys, I have another issue I want input on.  When child SMs 
terminate they have to notify their parent.  The parent has to wait for 
all the children to terminate.  So I've been thinking to use the job 
subsystem for this: the parent would post a job to wait for N children,
and each child would post a job, the last one releasing the parent.

Now I see two ways to implement this - one is to implement this directly 
in the state machine code.  The parent simply stops running (because it 
does not schedule a job yet returns DEFERRED).  Each child decrements a 
counter, and when it hits 0 the parent is restarted.  This is a little 
ugly because the waiting parent is not being held on any list or queue 
(up to now all waiting SMs are in the job subsystem), also the last 
terminating child becomes the parent as it starts executing the parent 
code.  Things can get weird when one SM starts children that start 
children, and so on.

Now the other way to implement this is with the job subsystem as I 
suggested above.  Much cleaner except for one thing:  up to now the 
state machine subsystem has had no dependency at all on the job 
subsystem.  If we do it this way, this function only works with the job 
system intact.  I'd prefer not to do this, but it does seem the 
cleanest, most logical means.

Comments?

Walt
-- 
Dr. Walter B. Ligon III
Associate Professor
ECE Department
Clemson University