Re: [PATCH] sched/fair: Fix kernel build warning in test_idle_cores() for !SMT NUMA

[Lukasz Luba]

On 2/27/20 2:02 PM, Mel Gorman wrote:
> Building against tip/sched/core as of as ff7db0bf24db ("sched/numa: Prefer
> using an idle CPU as a migration target instead of comparing tasks") with
> the arm64 defconfig (which doesn't have CONFIG_SCHED_SMT set) leads to:
>
>    kernel/sched/fair.c:1525:20: warning: â??test_idle_coresâ?? declared â??staticâ?? but never defined [-Wunused-function]
>     static inline bool test_idle_cores(int cpu, bool def);
> 		      ^~~~~~~~~~~~~~~
>
> Rather than define it in its own CONFIG_SCHED_SMT #define island, bunch it
> up with test_idle_cores().
>
> Fixes: ff7db0bf24db ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks")
> [mgorman@xxxxxxxxxxxxxxxxxxx: Edit changelog, minor style change]
> Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> ---
>   kernel/sched/fair.c | 14 +++++++++-----
>   1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index fcc968669aea..10f9e6729fcf 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -1520,9 +1520,6 @@ static inline bool is_core_idle(int cpu)
>   	return true;
>   }
>   
> -/* Forward declarations of select_idle_sibling helpers */
> -static inline bool test_idle_cores(int cpu, bool def);
> -
>   struct task_numa_env {
>   	struct task_struct *p;
>   
> @@ -1558,9 +1555,11 @@ numa_type numa_classify(unsigned int imbalance_pct,
>   	return node_fully_busy;
>   }
>   
> +#ifdef CONFIG_SCHED_SMT
> +/* Forward declarations of select_idle_sibling helpers */
> +static inline bool test_idle_cores(int cpu, bool def);
>   static inline int numa_idle_core(int idle_core, int cpu)
>   {
> -#ifdef CONFIG_SCHED_SMT
>   	if (!static_branch_likely(&sched_smt_present) ||
>   	    idle_core >= 0 || !test_idle_cores(cpu, false))
>   		return idle_core;
> @@ -1571,10 +1570,15 @@ static inline int numa_idle_core(int idle_core, int cpu)
>   	 */
>   	if (is_core_idle(cpu))
>   		idle_core = cpu;
> -#endif
>   
>   	return idle_core;
>   }
> +#else
> +static inline int numa_idle_core(int idle_core, int cpu)
> +{
> +	return idle_core;
> +}
> +#endif
>   
>   /*
>    * Gather all necessary information to make NUMA balancing placement

Looks good (apart from odd formatting got in 'â??') and calms down
yesterday's build of next (next-20200227 were I spotted it) and today's
also.

Reviewed-by: Lukasz Luba <lukasz.luba@xxxxxxx>

Regards,
Lukasz