AW: L4_ThreadSwitch behaviour

Hi Ben!
Now it's working! :-) I've changed two things:
a) I'm using a loop for time slice donation
b) I'm setting the prioriy of the Pager to 0xff (the same as roottask)

I assume after the Pagefault IPC was created, the Scheduler is run to select the next runnable thread - which is roottask. Thus the Pager is never executed.

But that seems unfair to me! Ping thread got donated a time slice but can't ever use it. Just because it creates a Pagfault at startup and thus sending an IPC is required, which in turn triggers the scheduler. But I suppose, that's life ... :-/

Cheers,

Martin.

-----Ursprüngliche Nachricht-----
Von: Ben Leslie [mailto:[email protected]] 
Gesendet: Donnerstag, 15. Februar 2007 21:53
An: Christian, Martin, OPEE45
Cc: [email protected]; [email protected]
Betreff: Re: L4_ThreadSwitch behaviour

On Thu Feb 15, 2007 at 17:27:41 +0100, Christian, Martin, OPEE45 wrote:
>My question is related to both L4Ka::Pistachio and
>NICTA::Pistachio-embedded, thus I'm mailing to both lists.
>
>Consider the following test cases:
>
>Case A
>======
>1. The root thread creates a new thread in a new address space (AS):
>   L4_ThreadControl( ping_tid, ping_tid, master_tid, L4_nilthread,
>                     L4_anythread, L4_anythread, NOUTCB )
>   L4_SpaceControl( ping_tid, 0, kip_area, utcb_area, &control )
>   L4_ThreadControl( ping_tid, ping_tid, master_tid, pager_tid,
>                     L4_anythread, L4_anythread, UTCB(0) )
>   L4_Start( ping_tid, (L4_Word_t)ping_stack + sizeof(ping_stack) - 32,
>             START_ADDR(testing_thread) )
>
>2. The root thread "refills" it's time slice (maybe that's bogus, but it
>is meant to ensure a full time slice is donated): L4_Yield();
>
>3. The root thread donates the rest of it's time slice to the new
>thread:
>   L4_ThreadSwitch( ping_tid );
>
>Case B
>======
>1. The root thread creates a new thread in a new AS
>2. The root thread waits for a startup IPC from the new thread (of
>course, the new thread has to be altered to send such an IPC)
>3. The root thread "refills" it's time slice
>4. The root thread donates the rest of it's time slice to the new thread
>
>Problem:
>Case A won't work, but Case B does. For Case A the new thread won't run,
>even though it's active and in the ready queue. The only difference is
>that in Case B the pages which hold the code are already mapped in the
>new threads AS.
>
>I think this is a generic issue, however I'm working with a "homemade"
>PowerPC Version of NICTA::Pistachio-embedded based on the Karlsruhe
>version.
>
>Questions:
>1.) Why does Case A fail (or at least don't do anything)?
>2.) Is there are difference between the semantics used in
>L4Ka::Pistachio and NICTA::Pistachio-embedded (or between X2 and N1)?
>
>Any opinions, experiences, fairy tales would be appreciated! :-)

OK, some guesses:

1/ What are the relative priorities of the thread in both cases?

2/ What is the pager doing in case A?

3/ What is the exact state of ping thread in case A (e.g: break into kdb
and dump thread state)

Cheers,

Benno