test_idle_cores()'s definition and all it's call sites are enclosed within CONFIG_SCHED_SMT. Hence the forward declaration needs to be conditionally enabled in order to prevent build warnings like the following. kernel/sched/fair.c:1524:20: warning: ‘test_idle_cores’ declared ‘static’ but never defined [-Wunused-function] static inline bool test_idle_cores(int cpu, bool def); ^~~~~~~~~~~~~~~ Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx> Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx> Cc: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Ben Segall <bsegall@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: sfr@xxxxxxxxxxxxxxxx Cc: linux-next@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> --- This patch solves a build problem that exists on next-20200302. kernel/sched/fair.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 84594f8..827087f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1521,7 +1521,9 @@ static inline bool is_core_idle(int cpu) } /* Forward declarations of select_idle_sibling helpers */ +#ifdef CONFIG_SCHED_SMT static inline bool test_idle_cores(int cpu, bool def); +#endif struct task_numa_env { struct task_struct *p; -- 2.7.4