Non-SMP l4Linux build fail

Stefan Kalkowski stefan.kalkowski at ...1...
Wed Feb 6 15:56:01 CET 2013

Hi Nikolay.

you're right L4Linux on top of Genode currently is bounded to have SMP
enabled in its configuration. Because you can configure how many virtual
cpus to use, and their mapping to physical ones anyway, by now I didn't
saw a reason to remove this constraint. Is it an actual problem for you
to have SMP enabled? Does it prevent you from using another
configuration option in the kernel?

Best regards

On 02/05/2013 12:56 PM, Nikolay Martyanov wrote:
> Hi, all!
> I've found one strange thing. May be someone here can help me. 
> If I try to build an l4Linux with no-SMP config, it results in a fail. 
> And here, I think, the reason:
> In l4lx lib we have file (ports-foc/src/lib/l4lx/
> Here we have a function l4lx_irq_dev_set_affinity() that uses non-lib
> (regular l4linux) function l4x_cpumask_copy(). This function declared in
> arch/l4/kernel/main.c
> In it's turn this function makes the following call:
>>> cpumask_copy(data->affinity, dest);
> as you can see, it uses an affinity member of irq_data struct.
> And this member is under l4linux config control: 
>>> #ifdef CONFIG_SMP
>>>  	cpumask_var_taffinity;
>>> #endif  
> So, as a result, if l4linux config doesn't provide this option - build
> fails.
> We can't use the same l4linux config directive in a lib to
> "turn off" this chain, because it is not available there.
> I have to change from SMP version to SMP from time to time, so as a
> solution I can wrap cpumask_copy(data->affinity, dest); in the same
> directive, but I don't think it's a good solutions.
> Have you any ideas?
> Best regards,
> Nikolay
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Stefan Kalkowski
Genode Labs ยท

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