[Xenomai-help] FPU not available in user-space programs

[Xenomai-help] FPU not available in user-space programs

[Rodrigo Rosenfeld Rosas]

Hi,

I was looking at /proc/xenomai/faults and noticed that the only errors 
were on TRAP 7 (FPU not available).

Each time I run the user-space program using the native skin, I 
increment the fault by one. I don't understand why this happens. From 
documentation, FPU should be enabled automatically for user-space programs.

Any ideas why I'm getting this error and what does it mean? Should I do 
some float-point operation before creating my real-time tasks?

Thanks in advance,

Rodrigo.


		
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Re: [Xenomai-help] FPU not available in user-space programs

[Jan Kiszka]

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Rodrigo Rosenfeld Rosas wrote:
> Hi,
> 
> I was looking at /proc/xenomai/faults and noticed that the only errors
> were on TRAP 7 (FPU not available).
> 
> Each time I run the user-space program using the native skin, I
> increment the fault by one. I don't understand why this happens. From
> documentation, FPU should be enabled automatically for user-space programs.
> 
> Any ideas why I'm getting this error and what does it mean? Should I do
> some float-point operation before creating my real-time tasks?
> 

Watch out for the thread "T_FPU without effect" on xenomai-core, I
stumbled over this some time ago as well. It's an initial fault that
happens only on first FPU usage from user-space.

I'm not up-to-date with its current state, i.e. if there are plans to
solve this differently. Maybe Gilles or Philippe can comment on it.

Jan


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Re: [Xenomai-help] FPU not available in user-space programs

[Gilles Chanteperdrix]

Rodrigo Rosenfeld Rosas wrote:
 > Hi,
 > 
 > I was looking at /proc/xenomai/faults and noticed that the only errors 
 > were on TRAP 7 (FPU not available).
 > 
 > Each time I run the user-space program using the native skin, I 
 > increment the fault by one. I don't understand why this happens. From 
 > documentation, FPU should be enabled automatically for user-space programs.
 > 
 > Any ideas why I'm getting this error and what does it mean? Should I do 
 > some float-point operation before creating my real-time tasks?

This fault is not an error, it happens when a task use the FPU for the
first time in primary mode. When in secondary mode, such an FPU fault
happens every time the FPU is used after a context switch, you simply do
not know about it because it is not accounted for.

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-help] FPU not available in user-space programs

[Rodrigo Rosenfeld Rosas]

Thank you Gilles and Jan,

Jan, I had taken a look at that thread just after I created this thread.

Well, at least, now I know this fault is expected and is not an error.

Do I need to make a dummy float-point operation in primary mode for avoiding 
unexpected higher latency for enabling FPU in critical code?

Thank you for your support. I must enforce that this list has the best support 
I've seen. I posted a question on Doxygen's user list a few days ago and just 
one user answered to it, but not really solved what I was asking...

By the way, does someone here know how can I put comment code on 
documentation, as in:
/*! ...
   \code /* this is a comment */ \endcode */

Of course this won't compile. The user suggests to put the above code inside a 
#ifdef __COMMENT__ and define it on Doxyfile, but that makes the code seem 
ugly in kdevelop, besides causing a compiler warning:

warning: "/*" within comment


Is there a cleaner way to make possible to put comments inside the @code 
command?

I hope you can help me once more this time... ;)

Thanks,

Rodrigo.

____________________________________________________________
Em Quinta 06 Julho 2006 08:33, Gilles Chanteperdrix escreveu:

>Rodrigo Rosenfeld Rosas wrote:
> > Hi,
> >
> > I was looking at /proc/xenomai/faults and noticed that the only errors
> > were on TRAP 7 (FPU not available).
> >
> > Each time I run the user-space program using the native skin, I
> > increment the fault by one. I don't understand why this happens. From
> > documentation, FPU should be enabled automatically for user-space
> > programs.
> >
> > Any ideas why I'm getting this error and what does it mean? Should I do
> > some float-point operation before creating my real-time tasks?
>
>This fault is not an error, it happens when a task use the FPU for the
>first time in primary mode. When in secondary mode, such an FPU fault
>happens every time the FPU is used after a context switch, you simply do
>not know about it because it is not accounted for.

	

	
		
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Re: [Xenomai-help] FPU not available in user-space programs

[Gilles Chanteperdrix]

Rodrigo Rosenfeld Rosas wrote:
 > Is there a cleaner way to make possible to put comments inside the @code 
 > command?

What about putting the commented code in a separate file and including
it with \include ?

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-help] FPU not available in user-space programs [Doxygen]

[Rodrigo Rosenfeld Rosas]

Gilles Chanteperdrix escreveu:
> Rodrigo Rosenfeld Rosas wrote:
>  > Is there a cleaner way to make possible to put comments inside the @code 
>  > command?
>
> What about putting the commented code in a separate file and including
> it with \include ?
>   
That is a good idea, but it does not worth in my case, since the code is 
too small.

But thanks for the suggestion.

Rodrigo.



	

	
		
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