Johan Cockx wrote:
>
>
> On Tue, Oct 12, 2010 at 3:38 PM, Gilles Chanteperdrix
> <gilles.chanteperd...@xenomai.org
> <mailto:gilles.chanteperd...@xenomai.org>> wrote:
>
> Gilles Chanteperdrix wrote:
> > Johan Cockx wrote:
> >>
> >> On Tue, Oct 12, 2010 at 3:04 PM, Gilles Chanteperdrix
> >> <gilles.chanteperd...@xenomai.org
> <mailto:gilles.chanteperd...@xenomai.org>
> >> > Ok: __real_socket is not called, the
> XENOMAI_SKINCALL3(...) code
> >> > returns zero in this case.
> >>
> >> Ok. zero should be translated in something like 1024 - 128.
> And the
> >> reverse operation happen in select code.
> >>
> >>
> >> If I understand you correctly, the socket call is returning a valid
> >> Xenomai file descriptor as it should. So, the next question is:
> why is
> >> this file descriptor (or the corresponding mask) not recognized
> as such
> >> in select()? Do you have any further suggestions on how to debug
> this?
> >
> > As I just explained. verify that __wrap_socket returns 1024 - 128, or
> > something like that. And that this value gets translated back to 0 in
> > select code.
>
> Normally, since there is only one file descriptor in the fdset, the test
> which fails should be first_fp_valid_p.
>
>
> I guess you are looking at the kernel code? I was still looking at the
> user space code for __wrap_select. The arguments of that function are
> as expected: nfds=897, and the bit for file descriptor 896 is set in
> __readfds. I guess the XENOMAI_SKINCALL5 macro expands to a kernel
> call, but sorry I have little experience with kernel programming. Does
> this go straight to the __select function in skins/posix/syscall.c? I
> can see the first_fp_valid_p call there.
You can assume that it goes straight. It is a bit more complex than
that, but the details do not really matter for this case.
>
> This is the function where I previously put a printk call. I just
> checked dmesg again, and the printk'd message now appears (it seems
> that `dmesg | tail -f` isn't working correctly for me, but `dmesg |
> tail` is). Also, when I change syscall.c, a `make-kpkg --rootcmd
> fakeroot --initrd kernel_image|`| at the top of the source tree somehow
> does not rebuild anything. Until now, I have done a clean + complete
> rebuild for the whole kernel for each change, but that takes quite some
> time. Is there a better way to do this?
Well, build your kernel without make_kpkg. But you can put printks all
over the places in select code, this will save you compilations.
--
Gilles.
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