Re: Ravenscar - release multiple tasks when an event occurs

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 2020-05-03 13:43, Simon Wright wrote:
> I have several sensor tasks (in general, 2 at the moment) which will of
> course be created and start execution during elaboration.

Depends on the value specified for pragma Partition_Elaboration_Policy. 
If it is Sequential, the tasks start only after (most of) elaboration is 
completed -- RM H.6.

> I'd like to ensure that they don't actually start reading and reporting
> input data until the system is in a state to receive them.

How/when does the system reach that state? At end of elaboration, or at 
some much later time? Should other tasks execute before that state is 
reached?

> With the Ravenscar profile it's not obvious how to do this (only one
> entry per PO, only one task allowed to queue).

You can of course create a special protected object for each sensor task 
that has an entry "wait until system in good state" and a procedure 
"declare system in good state" to open that entry.

Or you could do the same with Suspension_Objects from 
Ada.Synchronous_Task_Control (but Gnat implements them as protected 
objects anyway, I think).

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
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