linux-kernel - Re: [tip:sched/fifo 44/45] ERROR: modpost: "sched

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Message-ID: <20200721101357.xoa6x4xtzkqoltfk@e107158-lin>
Date:   Tue, 21 Jul 2020 11:13:58 +0100
From:   Qais Yousef <qais.yousef@....com>
To:     peterz@...radead.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Ingo Molnar <mingo@...nel.org>, sfr@...b.auug.org.au
Subject: Re: [tip:sched/fifo 44/45] ERROR: modpost: "sched_setscheduler"
 undefined!

On 07/21/20 10:36, peterz@...radead.org wrote:
> On Mon, Jul 20, 2020 at 06:19:43PM -0400, Steven Rostedt wrote:
> > On Mon, 20 Jul 2020 23:49:18 +0200
> > Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > Steve, would this work for you, or would you prefer renaming the
> > > parameters as well?
> > > 
> > 
> > Yeah, that's fine. You don't have any sched_fifo_high() ?
> 
> Thanks! and no.
> 
> I'll go write a Changelog and add it to tip/sched/fifo, so that
> hopefully, sfr can stop complaining about this build fail ;-)
> 
> I've even argued we should rename fifo_low() to something else, but
> failed to come up with a sensible name. The intended case is for when
> you want something above normal but don't particularly care about RT at
> all.
> 
> The thing is, once you start adding priorities, even low,med,high, we're
> back to where we were. And the whole argument is that the kernel cannot
> set priorities in any sensible fashion.

Agreed. I am worried about in-kernel users setting random uclamp values too.

This series should do most of the work but there are more pieces needed on-top.

>From what I see we still need to move the sched_setscheduler() from
include/linux/sched.h to kernel/sched/sched.h. And sched_setattr() too. The
latter has a single user in kernel/trace/trace_selftest.c to create a deadline
task. I think that can be easily wrapped with a similar sched_set_dl()
function and exported instead.

Happy to do the work if you nudge me after you've published this fix on tip or
your queue.

Thanks

--
Qais Yousef