Re: [PATCH] pip_stress: increase usleep for ARM devices

[Clark Williams <clark.williams@gmail.com>]

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On Wed, 10 Dec 2014 09:15:00 -0500
Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org> wrote:

> On 12/10/2014 03:25 AM, chase.qi@linaro.org wrote:
> > From: Chase Qi <chase.qi@linaro.org>
> >
> > Hello,
> >
> > pip_stress works out of the box on my x86 based laptop, but
> > doesn't work on ARM devices, returned 'no inversion incurred'.
> > Follow the comment to increase usleep value, 2500 worked for
> > pandaboard and 3000 worked for Beaglebone Black board.
> >
> > I propose that increase the usleep value to 3500 from upstream,
> > so that we can use pip_stress right out of the box.
> >
> > Please let me know if this is acceptable.
> 
> I think they should have modified main() to accept the lock time as a parameter
> instead of simply adding some instructions in the comments
> 
>  * to show that it works. If you are having difficulty triggering an inversion,
>  * merely increase the time that the low priority process sleeps while
>  * holding the lock. (usleep);
>  * Also note that you have to run as a user with permission to change
>  * scheduling priorities.
>  */
> 
> what I would do is actually
> 1. modify main to accept lock_time
> 2. send the patch to the rt-tests team
> 
> 
>

I wish we didn't have to deal with timers here. I used barriers when I
wrote pi_stress.c and obviously we don't have that luxury with
pip_stress.c. I guess the best thing we can do right now is add a
parameter to change the default timer value for pip_stress and see if
someone comes up with a brilliant state-machine solution that will work
between processes :).

John and I are about to start a sweep through the tests and will
probably come out with a new rt-tests around the first of the year. 

Clark

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