tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core-sched head: a2f7c8bee1740fc80a75734268b065c96d68d29b commit: 520bf37d416584c0aca5a190d922d4db145e5d91 [27/29] sched: Cgroup core-scheduling interface config: i386-randconfig-r003-20210413 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?... git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git git fetch --no-tags peterz-queue sched/core-sched git checkout 520bf37d416584c0aca5a190d922d4db145e5d91 # save the attached .config to linux build tree make W=1 ARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): kernel/sched/core.c:3166:6: warning: no previous prototype for 'sched_set_stop_task' [-Wmissing-prototypes] 3166 | void sched_set_stop_task(int cpu, struct task_struct *stop) | ^~~~~~~~~~~~~~~~~~~ kernel/sched/core.c: In function 'sched_core_cgroup_online': 5696 | if (parent->core_parent) { | ^~ At top level: kernel/sched/core.c:5712:22: warning: 'sched_core_cgroup_cookie' defined but not used [-Wunused-function] 5712 | static unsigned long sched_core_cgroup_cookie(struct task_group *tg) | ^~~~~~~~~~~~~~~~~~~~~~~~ kernel/sched/core.c:5707:13: warning: 'sched_core_cgroup_free' defined but not used [-Wunused-function] 5707 | static void sched_core_cgroup_free(struct task_group *tg) | ^~~~~~~~~~~~~~~~~~~~~~ kernel/sched/core.c:5692:13: warning: 'sched_core_cgroup_online' defined but not used [-Wunused-function] 5692 | static void sched_core_cgroup_online(struct task_group *parent, struct task_group *tg) | ^~~~~~~~~~~~~~~~~~~~~~~~ vim +5696 kernel/sched/core.c 5691 5692 static void sched_core_cgroup_online(struct task_group *parent, struct task_group *tg) 5693 { 5694 lockdep_assert_held(&cgroup_mutex); 5695 5697 WARN_ON_ONCE(parent->core_cookie); 5698 WARN_ON_ONCE(!parent->core_parent->core_cookie); 5699 tg->core_parent = parent->core_parent; 5700 5701 } else if (parent->core_cookie) { 5702 WARN_ON_ONCE(parent->core_parent); 5703 tg->core_parent = parent; 5704 } 5705 } 5706 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org