On Mon, 2010-04-19 at 09:37 +0200, Philippe Gerum wrote:
> On Mon, 2010-04-19 at 09:31 +0200, Jan Kiszka wrote:
> > Philippe Gerum wrote:
> > > On Sun, 2010-04-18 at 15:40 +0200, Jan Kiszka wrote:
> > >> Philippe Gerum wrote:
> > >>> On Sun, 2010-04-18 at 15:26 +0200, Philippe Gerum wrote:
> > >>>> On Sun, 2010-04-18 at 15:12 +0200, Jan Kiszka wrote:
> > >>>>> From: Jan Kiszka <jan.kis...@siemens.com>
> > >>>>>
> > >>>>> This adds rtdm_rt_capable(), a function that can be used by drivers to
> > >>>>> detect callers that could issue a service request also from the
> > >>>>> (typically preferred) real-time context. If that is the case, the
> > >>>>> driver
> > >>>>> can trigger a restart of the request if the current context is not
> > >>>>> real-time.
> > >>>>>
> > >>>>> CC: Philippe Gerum <r...@xenomai.org>
> > >>>>> CC: Alexis Berlemont <berlemont.h...@free.fr>
> > >>>>> Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
> > >>>>> ---
> > >>>>> include/rtdm/rtdm_driver.h | 6 ++++++
> > >>>>> ksrc/skins/rtdm/drvlib.c | 25 +++++++++++++++++++++++++
> > >>>>> 2 files changed, 31 insertions(+), 0 deletions(-)
> > >>>>>
> > >>>>> diff --git a/include/rtdm/rtdm_driver.h b/include/rtdm/rtdm_driver.h
> > >>>>> index 0fc1496..45be404 100644
> > >>>>> --- a/include/rtdm/rtdm_driver.h
> > >>>>> +++ b/include/rtdm/rtdm_driver.h
> > >>>>> @@ -1296,6 +1296,12 @@ static inline int rtdm_in_rt_context(void)
> > >>>>> {
> > >>>>> return (rthal_current_domain != rthal_root_domain);
> > >>>>> }
> > >>>>> +
> > >>>>> +static inline int rtdm_rt_capable(void)
> > >>>>> +{
> > >>>>> + return xnpod_shadow_p();
> > >>>>> +}
> > >>>>> +
> > >>>> This won't do what your comment states; xnpod_shadow_p() would always
> > >>>> return false on behalf of a relaxed shadow, since it tests the status
> > >>>> bits of the current Xenomai thread, which has to be the root one in
> > >>>> that
> > >>>> case. xnpod_shadow_p is to be used in primary context only, to
> > >>>> distinguish between kernel-based and userland Xenomai callers.
> > >>>>
> > >>>> What you want is probably something like:
> > >>>>
> > >>>> static inline int rtdm_rt_capable(void)
> > >>>> {
> > >>>> return xnshadow_thread(current) != NULL;
> > >>>> }
> > >>> Btw, the predicate as you defined it would not work over kernel-based
> > >>> Xenomai threads. rtdm_rt_capable() is ambiguous here.
> > >> (!xnpod_root_p() || xnshadow_thread(current) != NULL) ?
> > >>
> > >> That would also avoid dereferencing current in a potentially unsafe
> > >> context (if we still have such problematic archs).
> > >
> > > Depending on how precise you want that predicate to be,
> > >
> > > (!xnpod_asynch_p() && (!xnpod_root_p() || xnshadow_thread(current) !=
> > > NULL))
> > >
> > > may be better, in a sense that it also excludes IRQ handlers and nucleus
> > > callouts.
> >
> > IRQ handlers are not a valid invocation context (as documented). I don't
> > think it's worth bothering.
>
> No problem, I think the whole rtdm_rt_capable() approach leads to this
> kind of ambiguity by design anyway. So people should leave
s,leave,live,g
Interesting lapsus.
> with it and
> use that predicate in high level handler code only, where the current
> context can be assessed easily, not deep in their helpers or core
> routines which might be traversed by a broader set of callers.
>
> >
> > Jan
> >
>
>
--
Philippe.
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