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Re: AT91SAM7S256 problem with test/example twothreads


On Tue, 19 Jun 2012 22:18:14 +0200
Lambrecht Jürgen <J.Lambrecht@TELEVIC.com> wrote:

> On 06/19/2012 03:16 PM, Jesper K. Pedersen wrote:
> > On Sun, 17 Jun 2012 16:43:02 +0200
> > "Jesper K. Pedersen"<linux@famped.dk>  wrote:
> >
> >> I am at my wits end getting the twothreads example working on my
> >> Olimex P256 board (AT91SAM7S256 based).
> >>
> >> Calling the cyg_mutex_init does not return. Also I notice that the
> >> call to the printf line before the call to cyg_mutex_init prints
> >> extremely slow on my terminal.
> >>
> >> I have set the default console up to tty0 going to ser0. This part
> >> works fine with my other software running on the board (normal
> >> expected transmission speed).
> >>
> >> Are there any "gotcha'" involving threading on the AT91 series
> >> microcontrollers?
> >>
> > Problem was solved.
> >
> > For some reason if you put any output function (printf's) in the
> > cyg_user_start the threading will hang.
> >
> > Removing all output will allow for threading and the example works
> > as expected.
> >
> > I wonder if this is intended or if its a bug in the A91SAM7 eCos.
> >
> > Best regards
> > JesperKP
> >
> I have lots of diag_printf's in my cyg_user_start() running on an
> AT91 ARM7 and a ARM9.
> Maybe because you use printf?
> Be carefull:  Code running in initialization context runs with 
> interrupts disabled and the scheduler locked. Only after
> cyg_user_start, the scheduler starts and resumes all threads.
> Maybe (if I remember well; search the list for the diff between both 
> printfs) printf uses interrupts (to know when the hardware has sent a 
> byte), and diag_printf doesn't.
> 
> You must also realize that printf's can take a lot of CPU.
> 
> And no, it is certainly not intended or a bug in the ecos CVS code 
> (although I don't know the twothreads test): it is your bug ;-) .
> 

If you look in the ecos-3.0-user-guide.pdf on page 52 "A Sample Program
with Two Threads" it is shown with printf's in the cyg_user_start.

If that is not a correct way to do it - perhaps that example should be
changed? :-D

Best regards
JesperKP

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