linux-kernel - Re: [PATCH v3 2/3] sched: make migrate_enable/migrate

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Message-ID: <CAADnVQL0oWnQM2AJh=yzNtRmH2Mx=B-hM2xsvgEx2uqLEBQ5Dw@mail.gmail.com>
Date: Tue, 26 Aug 2025 19:58:02 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Benjamin Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, 
	Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	tzimmermann@...e.de, simona.vetter@...ll.ch, 
	Jani Nikula <jani.nikula@...el.com>, LKML <linux-kernel@...r.kernel.org>, 
	bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] sched: make migrate_enable/migrate_disable inline

On Thu, Aug 21, 2025 at 2:38 AM Menglong Dong <menglong8.dong@...il.com> wrote:
>
> +
> +#ifndef CREATE_MIGRATE_DISABLE
> +static inline void migrate_disable(void)
> +{
> +       __migrate_disable();
> +}
> +
> +static inline void migrate_enable(void)
> +{
> +       __migrate_enable();
> +}
> +#else /* CREATE_MIGRATE_DISABLE */
> +extern void migrate_disable(void);
> +extern void migrate_enable(void);
> +#endif /* CREATE_MIGRATE_DISABLE */

I think the explanation from the commit log is better to be
copy pasted here as a comment, since the need for the macro
is quite hard to understand.

> +
> +#else /* MODULE */
> +extern void migrate_disable(void);
> +extern void migrate_enable(void);
> +#endif /* MODULE */
> +

...
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index be00629f0ba4..58164a69449d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7,6 +7,8 @@
>   *  Copyright (C) 1991-2002  Linus Torvalds
>   *  Copyright (C) 1998-2024  Ingo Molnar, Red Hat
>   */
> +#define CREATE_MIGRATE_DISABLE
> +#include <linux/sched.h>

Also how about calling it
#define INSTANTIATE_EXPORTED_MIGRATE_DISABLE

When I asked AI what "instantiate exported migrate_disable"
means it guessed it nicely :)
while "create migrate_disable" had a vague answer.