Re: Task vs Protected Type

[Jean-Pierre Rosen <rosen@adalog.fr>]

S�bastien a �crit :
[...]

> The first one has the advantage to force the user to Initialize the task 
> because of the first entry, but there is no such mechanism in the 
> protected type.
The value of the mutex is given by the discriminant, no initialization 
needed.

> So in the wikibook, there is this sentence:
> "Alternatively, semaphore functionality can be provided by a protected 
> object, with major efficiency gains."
This is likely true on a bare board, I would be more careful when 
running under a conventional OS.

> For example, you have a web application and want to develop an object 
> pool. You could use one of both example, since it's the same purpose 
> with some GetObject and ReleaseObject enties/procedure in a task or in a 
> protected. But which one is the better approach?
> 
A task is a high level structure, a protected type is a low level 
synchronization mechanism.

However, implementing a low level mechanism (like a semaphore) with a 
task is certainly abstraction inversion. OTOH, if you use rendezvous, 
you can avoid semaphores altogether (in general of course, YMMV).

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            J-P. Rosen (rosen@adalog.fr)
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