Re: [Xenomai-core] rt_task_set_priority vs. Linux priority

[Philippe Gerum <rpm@xenomai.org>]

Gilles Chanteperdrix wrote:
> Philippe Gerum wrote:
>> Jan Kiszka wrote:
>>> So we should warn the user (in the doc) that rt_task_set_priority will
>>> leave an inconsistent priority distribution between Linux and Xenomai
>>> behind? But what is that propagation path in xnpod_renice_thread_inner
>>> good for then?
>>>
>> A failed attempt that used to work before the glibc folks decided to cache the
>> priority level of threads locally. With the NPTL, it's useless and error-prone.
> 
> I think linuxthreads already did the caching. So, in fact, it probably
> never really worked.

Great, that should make my answer to Jan even simpler:
Jan, please read: "A failed attempt".

> 
> But what is funny is that glibc people have (or had) problems with that
> caching too: when you passed priorities to pthread_create, whereas the
> kernel used the correct priority, the user-space was not aware of this
> priority, so pthread_getschedparam did not return the correct priority.
> Which is probably the reason why we need to call pthread_setschedparam
> in Xenomai libraries thread trampolines.
> 

Translation: it's a mess.

-- 
Philippe.