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Date:   Mon, 31 May 2021 09:33:57 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Bixuan Cui <cuibixuan@huawei.com>
Cc:     mingo@redhat.com, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -next] sched: make sched_set_stop_task() static
Message-ID: <YLSRZa0L79P+eSxk@hirez.programming.kicks-ass.net>
References: <20210529022956.43858-1-cuibixuan@huawei.com>
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On Sat, May 29, 2021 at 10:29:56AM +0800, Bixuan Cui wrote:
> make W=1 generates the following warning for kernel/sched/core.c:
> warning: no previous prototype for ‘sched_set_stop_task’ [-Wmissing-prototypes]
> 
> Signed-off-by: Bixuan Cui <cuibixuan@huawei.com>
> ---
>  kernel/sched/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index adea0b1e8036..1c1e9612018b 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3209,7 +3209,7 @@ int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
>  	return cpu;
>  }
>  
> -void sched_set_stop_task(int cpu, struct task_struct *stop)
> +static void sched_set_stop_task(int cpu, struct task_struct *stop)
>  {
>  	static struct lock_class_key stop_pi_lock;
>  	struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };

Clearly you tested this well...

$ git grep sched_set_stop_task
kernel/sched/core.c:void sched_set_stop_task(int cpu, struct task_struct *stop)
kernel/stop_machine.c:extern void sched_set_stop_task(int cpu, struct task_struct *stop);
kernel/stop_machine.c:  sched_set_stop_task(cpu, per_cpu(cpu_stopper.thread, cpu));

Please be more careful.