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Date:   Thu, 7 Nov 2019 07:25:25 +0000
From:   Patrick Bellasi <patrick.bellasi@matbug.net>
To:     Qais Yousef <qais.yousef@arm.com>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched: core: fix compilation error when cgroup not
 selected
Message-ID: <20191107072525.GA19642@darkstar>
References: <20191105112212.596-1-qais.yousef@arm.com>
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[ +Randy ]

Hi Qais,

On 05-Nov 11:22, Qais Yousef wrote:
> When cgroup is disabled the following compilation error was hit
> 
> 	kernel/sched/core.c: In function ‘uclamp_update_active_tasks’:
> 	kernel/sched/core.c:1081:23: error: storage size of ‘it’ isn’t known
> 	  struct css_task_iter it;
> 			       ^~
> 	kernel/sched/core.c:1084:2: error: implicit declaration of function ‘css_task_iter_start’; did you mean ‘__sg_page_iter_start’? [-Werror=implicit-function-declaration]
> 	  css_task_iter_start(css, 0, &it);
> 	  ^~~~~~~~~~~~~~~~~~~
> 	  __sg_page_iter_start
> 	kernel/sched/core.c:1085:14: error: implicit declaration of function ‘css_task_iter_next’; did you mean ‘__sg_page_iter_next’? [-Werror=implicit-function-declaration]
> 	  while ((p = css_task_iter_next(&it))) {
> 		      ^~~~~~~~~~~~~~~~~~
> 		      __sg_page_iter_next
> 	kernel/sched/core.c:1091:2: error: implicit declaration of function ‘css_task_iter_end’; did you mean ‘get_task_cred’? [-Werror=implicit-function-declaration]
> 	  css_task_iter_end(&it);
> 	  ^~~~~~~~~~~~~~~~~
> 	  get_task_cred
> 	kernel/sched/core.c:1081:23: warning: unused variable ‘it’ [-Wunused-variable]
> 	  struct css_task_iter it;
> 			       ^~
> 	cc1: some warnings being treated as errors
> 	make[2]: *** [kernel/sched/core.o] Error 1
> 
> Fix by protetion uclamp_update_active_tasks() with
> CONFIG_UCLAMP_TASK_GROUP
> 
> Fixes: babbe170e053 ("sched/uclamp: Update CPU's refcount on TG's clamp changes")
> Signed-off-by: Qais Yousef <qais.yousef@arm.com>

Thanks for posting this again.

We now have three "versions" of this same fix, including:
 - the original bug report by Randy and a fix from me here:
   Message-ID: <8736gv2gbv.fsf@arm.com>
   https://lore.kernel.org/linux-next/8736gv2gbv.fsf@arm.com/
 - and a follow up patch from Arnd:
   Message-ID: <20190918195957.2220297-1-arnd@arndb.de>
   https://lore.kernel.org/lkml/20190918195957.2220297-1-arnd@arndb.de/

So, I guess now we just have to pick the one with the changelog we
prefer. :)

In all cases we should probably add:

  Reported-by: Randy Dunlap <rdunlap@infradead.org>
  Tested-by: Randy Dunlap <rdunlap@infradead.org>

Best,
Patrick

> ---
>  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 dd05a378631a..afd4d8028771 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1073,6 +1073,7 @@ uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
>  	task_rq_unlock(rq, p, &rf);
>  }
>  
> +#ifdef CONFIG_UCLAMP_TASK_GROUP
>  static inline void
>  uclamp_update_active_tasks(struct cgroup_subsys_state *css,
>  			   unsigned int clamps)
> @@ -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)
>  {
> -- 
> 2.17.1
> 

-- 
#include <best/regards.h>

Patrick Bellasi