kernel/sched/ext.c:313:26: warning: 'scx_find_sub_sched' defined but not used

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   8ab992f815d6736b5c7a6f5fd7bfe7bc106bb3dc
commit: 25037af712eb04eb92a89440852029a50eea8d82 sched_ext: Add rhashtable lookup for sub-schedulers
date:   9 weeks ago
config: powerpc-randconfig-001-20260508 (https://download.01.org/0day-ci/archive/20260508/202605080556.42PXw8U9-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260508/202605080556.42PXw8U9-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Fixes: 25037af712eb ("sched_ext: Add rhashtable lookup for sub-schedulers")
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605080556.42PXw8U9-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from kernel/sched/build_policy.c:62:
   kernel/sched/ext.c: In function 'scx_vexit':
   kernel/sched/ext.c:5633:9: warning: function 'scx_vexit' might be a candidate for 'gnu_printf' format attribute [-Wsuggest-attribute=format]
    5633 |         vscnprintf(ei->msg, SCX_EXIT_MSG_LEN, fmt, args);
         |         ^~~~~~~~~~
   kernel/sched/ext.c: At top level:
>> kernel/sched/ext.c:313:26: warning: 'scx_find_sub_sched' defined but not used [-Wunused-function]
     313 | static struct scx_sched *scx_find_sub_sched(u64 cgroup_id) { return NULL; }
         |                          ^~~~~~~~~~~~~~~~~~
   In file included from kernel/sched/build_policy.c:52:
   kernel/sched/rt.c:12:18: warning: 'max_rt_runtime' defined but not used [-Wunused-const-variable=]
      12 | static const u64 max_rt_runtime = MAX_BW;
         |                  ^~~~~~~~~~~~~~


vim +/scx_find_sub_sched +313 kernel/sched/ext.c

   305	
   306	static void scx_set_task_sched(struct task_struct *p, struct scx_sched *sch)
   307	{
   308		rcu_assign_pointer(p->scx.sched, sch);
   309	}
   310	#else	/* CONFIG_EXT_SUB_SCHED */
   311	static struct scx_sched *scx_parent(struct scx_sched *sch) { return NULL; }
   312	static struct scx_sched *scx_next_descendant_pre(struct scx_sched *pos, struct scx_sched *root) { return pos ? NULL : root; }
 > 313	static struct scx_sched *scx_find_sub_sched(u64 cgroup_id) { return NULL; }
   314	static void scx_set_task_sched(struct task_struct *p, struct scx_sched *sch) {}
   315	#endif	/* CONFIG_EXT_SUB_SCHED */
   316	

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