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Date: Tue, 12 Jun 2007 20:10:46 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-core] CONFIG_SMP in switchtest
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai-core <xenomai@xenomai.org>

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
> 
>>Jan Kiszka wrote:
>>
>>>Philippe Gerum wrote:
>>>
>>>
>>>>On Tue, 2007-06-12 at 08:42 +0200, M. Koehrer wrote:
>>>>
>>>>
>>>>>Hi everybody,
>>>>>
>>>>>I want to know why the --enable-smp option for "configure" of Xenomai is used when there
>>>>>is already the corresponding option selected with the kernel configuration?
>>>>
>>>>--enable-smp is only used when you want the user-space side to _require_
>>>>SMP support to be present into the running kernel; i.e. for some (weird)
>>>>reason, your application really needs this. Xenomai libraries don't care
>>>>whether SMP support is enabled or not, they are not sensitive to that
>>>>issue (see the "weak" status of this option in README.INSTALL)
>>>
>>>Switchtest bases some compile-time decisions on CONFIG_SMP. Nitpicking,
>>>OK, but I wonder if this is required. Gilles?
>>
>>If you do not enable the smp option, switchtest will only use one cpu.
>>The reason why I made this is that, on some UP machine, (probably arm,
>>but I do no longer remember) sysconf(_SC_NPROCESSORS_ONLN) did not work.
> 
> 
> Welcome to embedded hell :-/. What was the effect precisely? Can we
> detect this during runtime? The point is I see people trying this test
> on SMP without providing the right switch to configure. Would be a pity
> IMHO.

I find the current behaviour consistent: if you do not enable smp, the
test only uses one CPU. But works.

-- 
                                                 Gilles Chanteperdrix