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Date: Thu, 01 Jan 2009 14:34:01 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] pthread cancelation and scheduling magics
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To: Wolfgang Grandegger <wg@domain.hid>
Cc: xenomai-help <xenomai@xenomai.org>

Wolfgang Grandegger wrote:
> Wolfgang Grandegger wrote:
>> Hi Gilles,
>>
>> Gilles Chanteperdrix wrote:
>>> Wolfgang Grandegger wrote:
>>>> I'm also puzzled why pthread_setschedparam() does make a mode switch
>>>> to secondary mode (sometimes).
>>> That is normal. The glibc caches threads priority value, so we have to
>>> call __real_pthread_setschedparam to update them. This issue has been
>>> solved differently on trunk, but unfortunately, we can not backport this
>>> modification on v2.4.x branch.
>> To get you right. With v2.4.x it is not possible with the POSIX skin to
>> change the priority of a real-time thread in the primary mode without
>> loosing determinism (because it will switch to secondary mode). What
>> options do I have?
> 
> I gave Xenomai trunk a try and pthread_setschedparam() does not switch
> to secondary mode any more on my PowerPC test system. Nice, I just get
> an Oops in thread_delete from time to time. More on that issue later.
> For my ARM i.mx31 system, a need a few patches to get the Xenomai src's
> compiled:
> 
> Index: include/asm-generic/bits/bind.h
> ===================================================================
> --- include/asm-generic/bits/bind.h	(revision 4450)
> +++ include/asm-generic/bits/bind.h	(working copy)
> @@ -72,7 +72,7 @@
>  	err = XENOMAI_SYSCALL1(__xn_sys_current, &current);
>  	if (err) {
>  		fprintf(stderr, "Xenomai: error obtaining handle for current "
> -			"thread: %s\n", strerror(err));
> +			"thread: %s\n", strerror(-err));
>  		exit(1);
>  	}
>  	__xeno_set_current(current);
> Index: include/asm-arm/syscall.h
> ===================================================================
> --- include/asm-arm/syscall.h	(revision 4450)
> +++ include/asm-arm/syscall.h	(working copy)
> @@ -228,7 +228,7 @@
>  	volatile unsigned long long *const tscp = __xn_tscinfo.u.fr.tsc;
>  	volatile unsigned *const counterp = __xn_tscinfo.u.fr.counter;
>          const unsigned mask = __xn_tscinfo.u.fr.mask;
> -	register unsigned long long after, before;
> +	register unsigned long long result;
>          unsigned counter;
>  
>          __asm__ ("ldmia %1, %M0\n": "=r"(result): "r"(tscp), "m"(*tscp));
> 
> 
> When I then start my application or cyclictest I get:
> 
> -bash-3.2# ./cyclictest -n 
> Xenomai: error obtaining handle for current thread: Operation not permitted
> 
> As the latency program works fine, it seems to be a problem with the
> POSIX skin. Any idea what it is?

What version of gcc are you using ? When trying to get xenomai running
on an ARM platform, I found out that gcc 4.3.1 and 4.3.2 have a bug on
ARM which thrashes the parameters passed to  some xenomai syscalls.

-- 
					    Gilles.