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Date: Wed, 21 Jan 2009 18:01:55 +0000
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] fpu issue
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To: Steven Seeger <sseeger@domain.hid>
Cc: xenomai@xenomai.org

Steven Seeger wrote:
> I have your output and it is repeatable every tiem.
> 
> Good case:
> 
> i387.c init_fpu()
> 
> xnarch_save_fpu() enters and takes the following path:
> 
> if(!tcb->is_root)
> if(task)
> if(!wrap_test_fpu_used(task)) return;
> 
> then, I see xnarch_restore_fpu take the following path:
> 
> tcb->is_root is set to 1, so it goes to else
> tcb->cr0_ts is true, so it calls stts() and returns;
> 
> bad case:
> 
> all the same, except tcb->cr0_ts is false. It leaves that if block,
> calls clts(), and then frstor instruction is called because I don't have
> fxsr
> 
> Is this helpful?
> 
> There are no calls to xnarch_enable_fpu or xnarch_init_fpu

Errr. Some things are missing, this is only one context switch (probably
the last ?). I would be interested in all the context switches since the
beginning of the process (hopefully, there should not be too much of them).

-- 
                                                 Gilles.