Re: longest path through a task

[jan.de.kruyf@gmail.com]

On Thursday, May 28, 2015 at 7:52:55 PM UTC+2, Simon Wright wrote:

> 
> I have been accused of terseness, sorry

It is an occupational disease, ask my wife.


> This is a Ravenscar runtime; the C interrupt handler has to invoke the
> Ada handler, which was registered by the Ada runtime when it saw a PO
> like
> 
>    protected Button
>    with
>      Interrupt_Priority => System.Interrupt_Priority'First
>    is
>       entry Wait_For_Trigger;
>    private
>       Triggered : Boolean := False;
>       procedure Handler;
>       pragma Attach_Handler (Handler, Ada.Interrupts.Names.EXTI0_IRQ);
>    end Button;
> 
> and I started timing in Button.Handler.
> 
> The corresponding task called Button.Wait_For_Trigger and I ended timing
> immediately on return.

Thanks, I think I remember coming to 5 usecs from glancing through the code, so it is even worse than that.

According to the gnat ravenscar profile they need that extra code layer to do things with locks and threads, but I could not tell you what anymore. I just cut my losses as explained above.

Here is the link to Matteo's page with the research papers on the subject.

http://inf.ethz.ch/personal/corti/

cheers,

j.