linux-kernel - Re: [PATCH v3 5/7] sched/preempt: add PREEMPT

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Date:   Thu, 10 Feb 2022 10:27:39 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, ardb@...nel.org,
        bp@...en8.de, catalin.marinas@....com, dave.hansen@...ux.intel.com,
        james.morse@....com, joey.gouly@....com, juri.lelli@...hat.com,
        linux-kernel@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        peterz@...radead.org, tglx@...utronix.de,
        valentin.schneider@....com, will@...nel.org
Subject: Re: [PATCH v3 5/7] sched/preempt: add PREEMPT_DYNAMIC using static
 keys

On Wed, Feb 09, 2022 at 06:48:01PM +0100, Frederic Weisbecker wrote:
> On Wed, Feb 09, 2022 at 03:35:33PM +0000, Mark Rutland wrote:
> > +config HAVE_PREEMPT_DYNAMIC_KEY
> > +	bool
> > +	depends on JUMP_LABEL
> 
> This should probably be:
> 
>      depends on HAVE_ARCH_JUMP_LABEL && CC_HAS_ASM_GOTO
>      select JUMP_LABEL
> 
> Otherwise you may run into trouble if CONFIG_JUMP_LABEL is initially n.

I'll make that:

 config HAVE_PREEMPT_DYNAMIC_KEY
        bool
        depends on HAVE_ARCH_JUMP_LABEL && CC_HAS_ASM_GOTO
        ...

... and 

 config PREEMPT_DYNAMIC
        bool "Preemption behaviour defined on boot"
        depends on HAVE_PREEMPT_DYNAMIC && !PREEMPT_RT
        select JUMP_LABEL if HAVE_PREEMPT_DYNAMIC_KEY
        ...

So that we don't force JUMP_LABEL on even when people aren't using it.

Thanks,
Mark.