From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 04 Dec 2008 11:11:58 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] Busy Loop Hang
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To: Matthew Fornero <matthew.fornero@domain.hid>
Cc: xenomai@xenomai.org

Matthew Fornero wrote:
> Hello,
> 
> I've created the following test case to illustrate linux and any tasks
> in the secondary domain hanging while executing a busy loop on one CPU
> in an SMP system.
> 
> Xenomai 2.4.5, Linux 2.6.26.5, x86_64
> Tests on quad-core AMD Opteron and dual-core Intel Core 2
> kernel booted with isolcpus=1-31
> 
> Task 1 (busy loop): Priority 99, CPU 1
> polls rt_timer_tsc until a timeout value is reached (1 ms)
> increments a counter (master counter)
> updates a global variable for the elapsed time
> every four minutes, goes to sleep with rt_task_sleep

This will not work. You can not prevent linux from working during 4
minutes and hope that it continue to work normally. For a minimal
perturbation of Linux, I would advise to suspend real-time activities
every 1/HZ seconds.

-- 
                                                 Gilles.