Re: [Xenomai-core] I-pipe patch for ARM S3C24xx (v4)

[Jan Kiszka <jan.kiszka@domain.hid>]

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Sebastian Smolorz wrote:
> Hi all,
> 
> now that the teething problems of my I-pipe port to the S3C24xx are cured 
> (hopefully ...) I'm going to iterate it to v4. We've established a project 
> homepage for that port
> http://opensource.emlix.com/ipipe-s3c24xx/
> in order to concentrate the source code and information at one point. Probably 
> tomorrow I will come up with a patch in order to address point 2 in my email 
> from 27.10.2006 ([1]). After that I can go to v5 of my patch and beg for 
> integration. :-)

Nice to hear.

> 
> However, there is one disturbing issue. When I execute
> 
> dd if=/dev/zero of=/dev/null
> 
> and the latency test in userspace with a period not less than 150 us the worst 
> case latency is about 220 us. But when I start latency with -p 100 I get a 
> softlock like the one attached. I guess this is the same problem as Detlef 
> Vollmann described in [2]. So I think it's time for a big fat ARM-specific 
> warning in the troubleshooting file and perhaps a modification of the 
> testsuite so that if being compiled for ARM the default sample periods are 
> greater than the 100 us now.

Something is preventing the watchdog kthread from being executed for
more than 10 s. Maybe this is just a sign that the systems is hopelessly
overloaded (what are average latencies?). Maybe it is a real IRQ or
scheduling issue in Linux caused by I-pipe. Maybe it is time to port the
I-pipe tracer... ;)

Jan


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