Re: [Xenomai-core] CONFIG_SMP in switchtest

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

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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.

At this chance: I also noticed problems with our sched_setscheduler
detection and bfin's uClibc. Compilations works, linking fails - they
provide headers, but lack implementations. Patch suggestion will follow.

And my pthread_spin_lock detection got nicely vaporised on bfin once
again. I'm considering to switch back to the original configure-based
detection.

Enough of the moaning.

Jan


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