linux-kernel - Re: [PATCH] sched/uclamp: fix building without cgroup

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Date:   Wed, 18 Sep 2019 21:38:22 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Patrick Bellasi <patrick.bellasi@....com>,
        Michal Koutny <mkoutny@...e.com>, Tejun Heo <tj@...nel.org>,
        Alessio Balsini <balsini@...roid.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Joel Fernandes <joelaf@...gle.com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Todd Kjos <tkjos@...gle.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/uclamp: fix building without cgroup

Hi Arnd,

On 18/09/2019 20:59, Arnd Bergmann wrote:
> The css_task_iter interfaces are defined conditionally and
> cause build failures when used in other configurations:
> 
> kernel/sched/core.c:1081:23: error: variable has incomplete type 'struct css_task_iter'
> kernel/sched/core.c:1084:2: error: implicit declaration of function 'css_task_iter_start' [-Werror,-Wimplicit-function-declaration]
> kernel/sched/core.c:1085:14: error: implicit declaration of function 'css_task_iter_next' [-Werror,-Wimplicit-function-declaration]
> kernel/sched/core.c:1091:2: error: implicit declaration of function 'css_task_iter_end' [-Werror,-Wimplicit-function-declaration]
> 
> As this code is unused anyway in that configuration, just put
> it into the same #ifdef. This also avoids possible warnings
> about unused inline functions.
> 
> Fixes: babbe170e053 ("sched/uclamp: Update CPU's refcount on TG's clamp changes")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Patrick's submitted the same thing at:

  https://lkml.kernel.org/r/8736gv2gbv.fsf@arm.com

so you may want to holler in that thread. Those kind of things really should
get caught by the 0day bot but it seems it's been on sick leave lately :/

> ---
>  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 f9a1346a5fa9..f25e3949a5ba 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1043,6 +1043,7 @@ static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
>  		uclamp_rq_dec_id(rq, p, clamp_id);
>  }
>  
> +#ifdef CONFIG_UCLAMP_TASK_GROUP
>  static inline void
>  uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
>  {
> @@ -1091,7 +1092,6 @@ uclamp_update_active_tasks(struct cgroup_subsys_state *css,
>  	css_task_iter_end(&it);
>  }
>  
> -#ifdef CONFIG_UCLAMP_TASK_GROUP
>  static void cpu_util_update_eff(struct cgroup_subsys_state *css);
>  static void uclamp_update_root_tg(void)
>  {
>