Re: [Corelinux-develop] Questions (again)

[Frank V. C. <fr...@co...>]

Hans - Dulimarta wrote:
> 
> I'm implementing EventSemaphore in the following setup:
> 
> Assuming we have three operations: down(), up(), and zero().

Are these the actual interface method names? While I don't feel the
requirements document quite addresses is, the semantics of an Event are
things more like hold/trigger/waitFor

> When an EvSem is created, its value is initialized to 1 indicating the
> expected event has not occured.

I assume this is 'up', which I would consider 'hold'.

> Any callers who are waiting for the event to occur will do a "lock"
> by calling zero(). When the event actually takes place, the semaphore will
> be released via the down() operation.

Terminology shift, callers 'waitFor' events no? and the owner 'triggers'
them (to trigger an Event)?

> The requirement document (SRS ?) for says that the Many-to-One semaphores
> will automatically lock upon creation and there is no option to create in
> unlock. When I look at the code, lock is similar to down() semaphore
> operation which implies that the creator will be block in the middle of
> the EventSemaphore ctor.
> 
> In the context of the above three operations, how can the creator perform
> a release operation to indicate that the expected event has occured?

There are two things to consider here:

1. As the SemaphoreGroup instantiates the creation of the Semaphore (in
this case EventSemaphore), it can construct and then call 'hold'.

2. The owner of a semaphore is not in a blocked state, the Linux kernel
semaphore has a state change, but the owner is not blocked. Only those
callers 'waiting for' an event are blocked.

Hope this helps.

> --
> Hans Dulimarta, Ph.D.                  dul...@co...
> P: 517-432-7589             http://www.egr.msu.edu/~dulimart
> F: 760-281-7691             http://corelinux.sourceforge.net
> Elec. & Comp. Engg., Mich. State Univ., E. Lansing, MI 48824
> 
> _______________________________________________
> Corelinux-develop mailing list
> Cor...@li...
> http://lists.sourceforge.net/mailman/listinfo/corelinux-develop

-- 
Frank V. Castellucci