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Date: Thu, 8 Jun 2006 20:42:31 +0200
Subject: Re: [Xenomai-core] [rfc] unit testing context switches.
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From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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	discussions\)" <xenomai.xenomai.org>
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To: Heikki Lindholm <holindho@domain.hid>
Cc: xenomai@xenomai.org

Heikki Lindholm wrote:
 > Gilles Chanteperdrix kirjoitti:
 > > Jan Kiszka wrote:
 > >  > Gilles Chanteperdrix wrote:
 > >  > > --- /dev/null	2006-05-03 22:25:59.000000000 +0200
 > >  > > +++ include/rtdm/rttesting.h	2006-06-07 18:50:14.000000000 +0200
 > >  > > @@ -0,0 +1,188 @@
 > >  > ...
 > >  > > + *
 > >  > > + * @{
 > >  > > + */
 > >  > > +
 > >  > > +#ifndef _RTBENCHMARK_H
 > >  > > +#define _RTBENCHMARK_H
 > >  > 
 > >  > Hmm, there might be further renamings required. Could you double-check
 > >  > (e.g. grep -ri benchmark)?
 > > 
 > > This particular define should be fixed in the version that I commited. 
 > > 
 > > I also put dummy asm/fptest.h for all other architectures than x86, I
 > > would now need volunteers with other hardware than x86 to implement
 > > asm/fptest.h for their platform and run the test.
 > > 
 > > A little explanation of what work should be done: two functions
 > > fp_regs_set and fp_regs_check should be implemented. fp_regs_set should
 > > set all fp registers to the integer value passed as
 > > argument. fp_regs_check should check that all fp registers are set to
 > > the integer value passed as argument, print the incorrect registers if
 > > any and return 1 if some register value is incorrect.
 > 
 > IMO setting every reg to a different value would be better, or like I 
 > did, calculate some value using every reg and only check the final 
 > result. That would also make pointer (to the fpu save area) 
 > corruptions/miscalculations and interruptions to the fpu save/restore 
 > routines better visible.

Every register is set to a different value by every task, so if
something goes wrong, it will not get unnoticed. Checking only a final
result will not tell you which context was badly switched, whereas the
current approach will, and will also tell you where the erroneous
register come from.

The implementor of fp_regs_set/fp_regs_check is also free to set every
register to a different value depending on the integer value passed as
argument but it is of limited interest.

-- 


					    Gilles Chanteperdrix.