Re: [ECOS] AT91SAM7S256 problem with test/example twothreads

[Lambrecht Jürgen <J dot Lambrecht at TELEVIC dot com>]

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 ;-) .

Success,
Jürgen

-- 
Jürgen Lambrecht
R&D Associate
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