Re: protected type interrupts

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

Adam Beneschan a �crit :
> I'm just reading what the RM says.  But, although I'm not an expert at
> this, I don't believe your argument makes sense given the way protected
> objects are supposed to work.  A task cannot, of course, access data
> internal to a protected object directly; it has to call one of the PO's
> subprograms or entries to get it.  When it does so, then assuming
> Ceiling_Locking is in effect, no other task can use the PO---but it's
> not because other tasks are blocked, it's simply because the protected
> action runs at a higher priority than any task that could use the PO
> (and the protected action is supposed to complete very quickly).  So no
> mutual exclusion or blocking is necessary when calling protected
> subprograms.  At least I think that's how it works.
> 
Hmmm... yes, as long as you are running on a mono-processor. But the 
rules must take care of multi-processors, too. In that case, there is 
some blocking, but it can be implemented by spin-locking, thus avoiding 
context switches (see my previous message).

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