linux-kernel - Re: [PATCH v2 2/5] preempt/dynamic: Introduce preempt mode accessors

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Message-ID: <a7febd8825a2ab99bd1999664c6d4aa618b49442.camel@gmx.de>
Date:   Thu, 11 Nov 2021 04:47:28 +0100
From:   Mike Galbraith <efault@....de>
To:     Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linuxppc-dev@...ts.ozlabs.org, linux-kbuild@...r.kernel.org
Cc:     Marco Elver <elver@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v2 2/5] preempt/dynamic: Introduce preempt mode accessors

On Thu, 2021-11-11 at 04:35 +0100, Mike Galbraith wrote:
> On Thu, 2021-11-11 at 04:16 +0100, Mike Galbraith wrote:
> > On Wed, 2021-11-10 at 20:24 +0000, Valentin Schneider wrote:
> > >
> > > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > > index 5f8db54226af..0640d5622496 100644
> > > --- a/include/linux/sched.h
> > > +++ b/include/linux/sched.h
> > > @@ -2073,6 +2073,22 @@ static inline void cond_resched_rcu(void)
> > >  #endif
> > >  }
> > >  
> > > +#ifdef CONFIG_PREEMPT_DYNAMIC
> > > +
> > > +extern bool is_preempt_none(void);
> > > +extern bool is_preempt_voluntary(void);
> > > +extern bool is_preempt_full(void);
> > > +
> > > +#else
> > > +
> > > +#define is_preempt_none() IS_ENABLED(CONFIG_PREEMPT_NONE)
> > > +#define is_preempt_voluntary()
> > > IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)
> > > +#define is_preempt_full() IS_ENABLED(CONFIG_PREEMPT)
> >
> > I think that should be IS_ENABLED(CONFIG_PREEMPTION), see
> > c1a280b68d4e.
> >
> > Noticed while applying the series to an RT tree, where tglx
> > has done that replacement to the powerpc spot your next patch
> > diddles.
>
> Damn, then comes patch 5 properly differentiating PREEMPT/PREEMPT_RT.

So I suppose the powerpc spot should remain CONFIG_PREEMPT and become
CONFIG_PREEMPTION when the RT change gets merged, because that spot is
about full preemptibility, not a distinct preemption model.

That's rather annoying :-/

	-Mike