[Embedlets-dev] Re: Thread prioritization.

[Andrzej J. T. <an...@ch...>]

> What is the problem with bypassing the container involvment and relying on the
> RTOS thread priortization to manage the thread switch? That is what it is
> there for!

Not every platform we are targeting provides this capability, so we might 
have to provide different implementations on different platforms.  The TINI 
doesn't have thread priorities, I believe.

However, this might be a nice solution for those platforms that do provide 
RTOS thread prioritization.  What I would do is have the send() method raise 
it's thread priority higher than the async event queue handling threads, send 
the sync event, then return it's priority to it's starting value.  That would 
effectively block the async threads from executing during the sync event 
propagation.

> 1. The sendEvent(Event) method being thread-safe for synchronous events

I believe it is already.

> 2. Events would store their own consumer collection (or an event per
> consumer)

I've thought about this already.  This is a non-trivial thing to implement 
compared to how it is currently done (separate event queue and registered 
consumer collection, with matching done when the event is "ready" to be 
propagated, immediately with sync, handled  later by the async event 
dispatcher thread).

The problem you run into with having events track their own collection of 
consumers is that a consumer can be registered or deregistered at any time, 
which implies that you have to scan the whole list of queued events every 
time a consumer registration changes, and update each events individual 
consumer collection.  With wildcard matching on event types on the part of 
consumers, this involves a LOT of duplicate checking (since a consumer could 
easily appear in more than one event's collection), lots of overhead, and 
some pretty complex threaded code (with lots of thread synchronization 
issues), without a lot of benefit to show for it.

So I've left it simple at the moment, keeping separate track of event queues 
and registered consumers.

Andrzej Jan Taramina
Chaeron Corporation: Enterprise System Solutions
http://www.chaeron.com