Gnat and priority level

Gnat and priority level

[mferracini]

Hi, i'm new on ada and i have many problem... :)

i need an info:
Ada.Text_Io.Put(Item => Integer'image(System.Priority'Last));
and gnat on windows2000 replay "30"

but i need more level of priority (255): how i can do?(if i can, of
course)

thanks
maurizio

Re: Gnat and priority level

[Martin Krischik]

mferracini wrote:

> Hi, i'm new on ada and i have many problem... :)
> 
> i need an info:
> Ada.Text_Io.Put(Item => Integer'image(System.Priority'Last));
> and gnat on windows2000 replay "30"
> 
> but i need more level of priority (255): how i can do?(if i can, of
> course)

You can't do more the the OS or tasking layer got to offer. The only option
left it to map the 255 levels you want to use to the 32 (0..31, 31=
Interrupt) available.

With Regards

Martin
-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com

Re: Gnat and priority level

[Alex R. Mosteo]

mferracini wrote:
> Hi, i'm new on ada and i have many problem... :)
> 
> i need an info:
> Ada.Text_Io.Put(Item => Integer'image(System.Priority'Last));
> and gnat on windows2000 replay "30"
> 
> but i need more level of priority (255): how i can do?(if i can, of
> course)

You can't (at least easily). Not only the gnat implementation uses just 
32 priorities, but these are mapped to underlying windows priorities, 
which are only 7, if I remember correctly (yes, there's overlapping).

Take a look at the spec of System for more details.

If you need to play with real time semantics in gnat, be prepared to 
have only 6 priorities (plus interruptions) and don't forget to specify 
the ceiling locking policy, since that causes the executable to be put 
in the windows real time priority class. Failing to do so, the dynamic 
priorities of windows regular processes will screw up any attempt to 
test tasking priorities semantics.

Cheers!

Re: Gnat and priority level

[mferracini]

>You can't (at least easily). Not only the gnat implementation uses
just
>32 priorities, but these are mapped to underlying windows priorities,
>which are only 7, if I remember correctly (yes, there's overlapping).

and with Linux rt version like RT-Linux there are the some problem?
thanks again.

Re: Gnat and priority level

[Alex R. Mosteo]

mferracini wrote:
>>You can't (at least easily). Not only the gnat implementation uses
> 
> just
> 
>>32 priorities, but these are mapped to underlying windows priorities,
>>which are only 7, if I remember correctly (yes, there's overlapping).
> 
> 
> and with Linux rt version like RT-Linux there are the some problem?
> thanks again.

Take the following with a grain of salt, since I'm much less experienced 
with gnat for linux.

Firstly, I think that gnat doesn't target the RT capabilities of 
RT-Linux, so you'll really have regular non-RT linux threads. Unless 
someone has a patch for it.

Second, you can choose two threading implementations with gnat for linux:

* linux native threads, whose particularities I don't know but some 
linux expert could tell you (BTW, using the old 2.4 thread 
implementation, not the new 2.6 one).

* fsu-threads (I think) which if I remember correctly are 
POSIX-compliant or something-else-compliant which native linux's aren't. 
Those have the particularity that you have a single linux process, so a 
blocking call in any fsu-thread will block all the others (i.e. the 
linux thread is blocked).

Someone more experienced can confirm these things? I'm interested in the 
details too.

Re: Gnat and priority level

[Jerome Hugues]

In article <4174F7FA.1020705@mailinator.com>, Alex R. Mosteo wrote:
> mferracini wrote:
> Firstly, I think that gnat doesn't target the RT capabilities of 
> RT-Linux, so you'll really have regular non-RT linux threads. Unless 
> someone has a patch for it.

There exists one project on this subject

http://bernia.upv.es/rtportal/apps/rtl-gnat/

Note that I've never tried it, so I cannot comment on which GNAT
version it uses, ACATS results, etc

> Second, you can choose two threading implementations with gnat for linux:
> 
> * linux native threads, whose particularities I don't know but some 
> linux expert could tell you (BTW, using the old 2.4 thread 
> implementation, not the new 2.6 one).
> 
> * fsu-threads (I think) which if I remember correctly are 
> POSIX-compliant or something-else-compliant which native linux's aren't. 

Strict Annex D (real time) compliancy

See

http://gcc.gnu.org/onlinedocs/gnat_ugn_unw/Choosing-between-Native-and-FSU-Threads-Libraries.html

for more details

HTH

-- 
Jerome