Gilles Chanteperdrix wrote:
Philippe Gerum wrote:
 > > What about keeping SCHED_RR as the default scheduling policy and
 > > requiring users to manually select SCHED_NORMAL in thread creation
 > > attributes in order to create hybrid threads with pthread_create ?
> > > > No objection a priori, but what would this buy us?

As a user, I would expect pthread_create and pthread_setschedparam to
allow the same scheduling policies and priorities.

Is your concern about having the POSIX skin in kernel space currently assuming that SCHED_OTHER == SCHED_RR, which would be different than Linux's perception in that case?

However, I really think that we should not rely on implicit rules when we could avoid it (e.g. SCHED_RR as default), especially when those rules are going to be most often overlooked (people are rather used to default to SCHED_NORMAL/OTHER in the Linux sense).

What I suggested was to let people create normal threads using pthread_create (likely conforming to the SCHED_OTHER policy), then use the redirected pthread_setschedparam syscall (i.e. always applied to the current thread) to promote them as Xenomai shadows, but leave them in their original scheduling class. The same goes for rt_task_shadow. This would be explicit actions that would not leave much room for "surprises".



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