Gilles Chanteperdrix wrote:
Philippe Gerum wrote:
> Jan Kiszka wrote:
> > Hi,
> > this is an experimental hack to open the non-rt priority levels of Linux
> > to Xenomai shadow threads, i.e. allow shadows to be scheduled under
> > SCHED_NORMAL when in secondary mode. The scenario are typical borderline
> > threads between RT and non-RT: they share a critical code path with RT
> > threads, maybe mutex protected, but they are mostly time-sharing threads
> > which do not need SCHED_FIFO for this.
> > The patch (be careful, quick-hack!) addresses the prio level 0 in the
> > ipipe patch, the nucleus/shadow subsystem, and the native skin. A quick
> > test with the attached demo showed the expected behaviour so far: no
> > lock-up during busy-waiting in secondary mode, prio-boost when holding
> > the lock (visible via /proc/xenomai/sched), no obvious side effects.
> > Any comments? Does this break other things in a subtle way?
> An initial comment on the general usage of this extension: since the
> threads running in SCHED_OTHER/SCHED_NORMAL mode are expected to run
> non-RT workloads while still being able to use the RT infrastructure for
> communicating with the rest of the RT system, I think that the best
> places for creating such hybrids are in the rt_task_shadow (native skin)
> and pthread_setschedparam (POSIX skin) calls, which would make it clear
> that a regular Linux thread is involved [and as such needs to be created
> by a normal call to pthread_create()], which also happens to benefit
> from the RT infrastructure mainly for communication/sychronization purpose.
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?
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