timed entry call doesnt timeout

timed entry call doesnt timeout

[Vincent Smeets]

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Hallo,

gnat 3.13p on Solaris 2.6. I have added a little demo file.

I am writing a driver for an network protocol which will send data and
wait for an acknowledgement. I have implemented it in a package (Pkt)
with a procedure interface. Inside this package, I use a protected type
and the requeue statement to implement an action with a timeout.

If I directly call the interface (Pkt.Proc) it works OK. I get the
expected timeout. But if I call the interface from an extra protected
type, then the timeout doesn't occure. The call will hang forever.

In my case, it isn't a big problem because I am writing the other parts
of the program too. But what is the correct way? If I write a package
like this and let someone else call the procedures from my package. In
that case, I can't be sure that the other programmer isn't using
protected types to call my package.

Thanks,
Vincent


-- 
Vincent Smeets
SchlumbergerSema -
Competence Center Informatik GmbH 
Lohberg 10 - 49716 Meppen - Germany
tel:  +49 5931-805-461
fax:  +49 5931-805-175
mail: VSmeets@slb.com
web:  www.cci.de

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with Ada.Text_IO;

procedure Demo is

   package Pkt is
      procedure Proc;
   end Pkt;

   package body Pkt is
      protected Prot is
	 entry Proc;
      private
	 entry Proc_Wait;
      end Prot;

      protected body Prot is
	 entry Proc when True is
	 begin
	    Ada.Text_IO.Put_Line ("Pkt.Prot.Proc");
	    requeue Proc_Wait with abort;
	 end Proc;
	 entry Proc_Wait when False is
	 begin
	    Ada.Text_IO.Put_Line ("Pkt.Prot.Proc_Wait");
	 end Proc_Wait;
      end Prot;

      procedure Proc is
      begin
	 Ada.Text_IO.Put_Line ("Pkt.Proc: start");
	 select
	    Prot.Proc;
	    Ada.Text_IO.Put_Line ("Pkt.Proc: Prot.Proc OK");
	 or
	    delay 1.0;
	    Ada.Text_IO.Put_Line ("Pkt.Proc: Prot.Proc timeout");
	 end select;
      end Proc;
   end Pkt;

   protected Outside_Prot is
      procedure Proc;
   end Outside_Prot;

   protected body Outside_Prot is
      procedure Proc is
      begin
	 Ada.Text_IO.Put_Line ("Outside_Prot.Proc: start");
	 Pkt.Proc;
      end Proc;
   end Outside_Prot;

begin
   Pkt.Proc;
   Outside_Prot.Proc;
end Demo;

Re: timed entry call doesnt timeout

[Matthew Heaney]

"Vincent Smeets" <VSmeets@meppen.sema.slb.com> wrote in message
news:3C42A089.998D3EA0@meppen.sema.slb.com...
> I am writing a driver for an network protocol which will send data and
> wait for an acknowledgement. I have implemented it in a package (Pkt)
> with a procedure interface. Inside this package, I use a protected type
> and the requeue statement to implement an action with a timeout.

Why are you making "potentially blocking" calls to Text_IO from inside a
protected object?

Re: timed entry call doesnt timeout

[Vincent Smeets]

Matthew Heaney wrote:
> 
> "Vincent Smeets" <VSmeets@meppen.sema.slb.com> wrote in message
> news:3C42A089.998D3EA0@meppen.sema.slb.com...
> > I am writing a driver for an network protocol which will send data and
> > wait for an acknowledgement. I have implemented it in a package (Pkt)
> > with a procedure interface. Inside this package, I use a protected type
> > and the requeue statement to implement an action with a timeout.
> 
> Why are you making "potentially blocking" calls to Text_IO from inside a
> protected object?

The call to Text_IO is just for the demostroation in my example.

The point is that you can't see the use of my timed select statement at
the  outside of the package. There is no problem if it is called
externaly from the main program (it will give the timeout), but it may
not be called from a protected type (which will block forever).

-- 
Vincent Smeets
SchlumbergerSema -
Competence Center Informatik GmbH 
Lohberg 10 - 49716 Meppen - Germany
tel:  +49 5931-805-461
fax:  +49 5931-805-175
mail: VSmeets@slb.com
web:  www.cci.de