Gilles Chanteperdrix wrote:
> Redirecting to xenomai core.
> 
> Jan Kiszka wrote:
>> Gilles Chanteperdrix wrote:
>>> Because of __xn_exec_current, people have broken drivers, and user-space
>>> applications using T_PRIMARY as a broken way to workaround these broken
>>> drivers, and by maintaining compatibility, we let them keep their broken
>>> drivers and applications, by changing to the more natural
>>> __xn_exec_conforming and removing T_PRIMARY, we ask them to fix their
>>> drivers and applications.
>> Right goal, wrong approach for the reason I pointed out to Philippe:
>>
>> We cannot map all kinds of driver requirements on a single
>> __xn_exec_current in the RTDM middle layer.
> 
> What requirement can we not handle? It looks to me like with
> __xn_exec_conforming, we can handle any requirement.
> 
> The only problem being the "double context switch" issue. But as
> Philippe said, a sane application is calling such ioctls from non
> critical code, so this is in fact a non-issue.

And this is one of the restrictions I don't want to keep for upcoming
versions. Think of a POSIX app that creates threads, even non-RT ones.
Those are automatically shadowed. If those threads perform lots of
non-RT service requests on RTDM drivers, they will suffer.

The decision about conforming switches is really only driver business.
RTDM can only support the driver by providing all required information.

Jan