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Date: Tue, 21 Aug 2018 09:38:34 +0200
From: Juri Lelli <juri.lelli@gmail.com>
Subject: Re: SCHED_DEADLINE as user
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To: Tim Blechmann <tim@klingt.org>
Cc: Daniel Bristot de Oliveira <daniel@bristot.me>, linux-rt-users@vger.kernel.org, Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>, Luca Abeni <luca.abeni@santannapisa.it>, Alessio Balsini <alessio.balsini@santannapisa.it>

On 21/08/18 00:45, Tim Blechmann wrote:

[...]

> apart from that, i'm only missing two features:
> 
> * using SCHED_DEADLINE from user applications is kind of a showstopper
> for me

Right. Would you be up for continuing experimenting with DEADLINE (while
we get our heads around removing this constraint) by - ugly hack warning
- removing the check at

https://elixir.bootlin.com/linux/latest/source/kernel/sched/core.c#L4216

?

I guess it would be good if you could provide even more feedback than
you already did, so that we can plan ahead what needs fixing/changing or
implementing.

BTW, thanks a lot already for this discussion! :-)

> * a nicer glibc wrapper, that allows me to use pthreads rather than
> using `syscall`: it's all pretty easy to obtain the `tid` for a calling
> thread (gettid), but it seems to be impossible to obtain the `tid` from
>  `pthread_t` without some hacks which are way too dirty to share in
> public ...

Indeed. We have been basically relying on

https://github.com/scheduler-tools/rt-app/tree/master/libdl

so far. But, I guess it's time - it has been time for a while - that we
reach glibc guys and try to understand why this is not yet all in the
standard libraries.