linux-kernel - Re: [PATCH] sched: Split preemption model selection between DYNAMIC & !DYNAMIC

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Date:   Wed, 10 Nov 2021 05:37:48 +0100
From:   Mike Galbraith <efault@....de>
To:     Frederic Weisbecker <frederic@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] sched: Split preemption model selection between DYNAMIC
 & !DYNAMIC

On Wed, 2021-11-10 at 02:17 +0100, Frederic Weisbecker wrote:
> On Tue, Nov 09, 2021 at 03:10:57PM +0000, Valentin Schneider wrote:
> > +choice
> > +       prompt "Default boot-time Preemption Model"
> > +       depends on PREEMPT_DYNAMIC
> > +       default PREEMPT_NONE_BEHAVIOUR
> > +       help
> > +         This option defines the default preemption model of the kernel
> > +         if it hasn't been specified by the "preempt=" command line parameter.
> >  
> > -config PREEMPT_VOLUNTARY
> > -       bool
> > +config PREEMPT_NONE_BEHAVIOUR
> > +       bool "No Forced Preemption (Server)"
> >  
> > -config PREEMPT
> > -       bool
> > -       select PREEMPTION
> > -       select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
> > +config PREEMPT_VOLUNTARY_BEHAVIOUR
> > +       bool "Voluntary Kernel Preemption (Desktop)"
> > +
> > +config PREEMPT_BEHAVIOUR
> > +       bool "Preemptible Kernel (Low-Latency Desktop)"
> > +endchoice
>
> The problem here is that you're duplicating the existing titles
> for the static entries and you're losing all the help that text that used to come
> along. The point of the BEHAVIOUR thing, further mapping to either
> static or dynamic preemption, was to avoid that duplication and keep the
> same titles and help for the three behaviour, whether static or dynamic.

Adding "depends on !PREEMPT_DYNAMIC" to the first (legacy?) choice made
it appear/disappear at the appropriate time as well, but I have no idea
how duplication of help text can be avoided.

	-Mike