[android-common:android12-5.10-2025-12 0/1] kernel/sched/psi.c:1147:6: warning: no previous prototype for 'psi_trigger_destroy'

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

Hi Suren,

FYI, the error/warning still remains.

tree:   https://android.googlesource.com/kernel/common android12-5.10-2025-12
head:   730d06ec05ff5dc34389ff99ea4009411efba5e6
commit: d4e4e61d4a5b87bfc9953c306a11d35d869417fd [0/1] psi: Fix uaf issue when psi trigger is destroyed while being polled
config: i386-buildonly-randconfig-003-20260408 (https://download.01.org/0day-ci/archive/20260408/202604082001.sdkFC8LG-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260408/202604082001.sdkFC8LG-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
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604082001.sdkFC8LG-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/sched/psi.c:1077:21: warning: no previous prototype for 'psi_trigger_create' [-Wmissing-prototypes]
    1077 | struct psi_trigger *psi_trigger_create(struct psi_group *group,
         |                     ^~~~~~~~~~~~~~~~~~
>> kernel/sched/psi.c:1147:6: warning: no previous prototype for 'psi_trigger_destroy' [-Wmissing-prototypes]
    1147 | void psi_trigger_destroy(struct psi_trigger *t)
         |      ^~~~~~~~~~~~~~~~~~~
   kernel/sched/psi.c:1214:10: warning: no previous prototype for 'psi_trigger_poll' [-Wmissing-prototypes]
    1214 | __poll_t psi_trigger_poll(void **trigger_ptr,
         |          ^~~~~~~~~~~~~~~~
   kernel/sched/psi.c:1329:30: warning: 'psi_cpu_proc_ops' defined but not used [-Wunused-const-variable=]
    1329 | static const struct proc_ops psi_cpu_proc_ops = {
         |                              ^~~~~~~~~~~~~~~~
   kernel/sched/psi.c:1320:30: warning: 'psi_memory_proc_ops' defined but not used [-Wunused-const-variable=]
    1320 | static const struct proc_ops psi_memory_proc_ops = {
         |                              ^~~~~~~~~~~~~~~~~~~
   kernel/sched/psi.c:1311:30: warning: 'psi_io_proc_ops' defined but not used [-Wunused-const-variable=]
    1311 | static const struct proc_ops psi_io_proc_ops = {
         |                              ^~~~~~~~~~~~~~~


vim +/psi_trigger_destroy +1147 kernel/sched/psi.c

  1146	
> 1147	void psi_trigger_destroy(struct psi_trigger *t)
  1148	{
  1149		struct psi_group *group;
  1150		struct task_struct *task_to_destroy = NULL;
  1151	
  1152		/*
  1153		 * We do not check psi_disabled since it might have been disabled after
  1154		 * the trigger got created.
  1155		 */
  1156		if (!t)
  1157			return;
  1158	
  1159		group = t->group;
  1160		/*
  1161		 * Wakeup waiters to stop polling. Can happen if cgroup is deleted
  1162		 * from under a polling process.
  1163		 */
  1164		wake_up_interruptible(&t->event_wait);
  1165	
  1166		mutex_lock(&group->trigger_lock);
  1167	
  1168		if (!list_empty(&t->node)) {
  1169			struct psi_trigger *tmp;
  1170			u64 period = ULLONG_MAX;
  1171	
  1172			list_del(&t->node);
  1173			group->nr_triggers[t->state]--;
  1174			if (!group->nr_triggers[t->state])
  1175				group->poll_states &= ~(1 << t->state);
  1176			/* reset min update period for the remaining triggers */
  1177			list_for_each_entry(tmp, &group->triggers, node)
  1178				period = min(period, div_u64(tmp->win.size,
  1179						UPDATES_PER_WINDOW));
  1180			group->poll_min_period = period;
  1181			/* Destroy poll_task when the last trigger is destroyed */
  1182			if (group->poll_states == 0) {
  1183				group->polling_until = 0;
  1184				task_to_destroy = rcu_dereference_protected(
  1185						group->poll_task,
  1186						lockdep_is_held(&group->trigger_lock));
  1187				rcu_assign_pointer(group->poll_task, NULL);
  1188				del_timer(&group->poll_timer);
  1189			}
  1190		}
  1191	
  1192		mutex_unlock(&group->trigger_lock);
  1193	
  1194		/*
  1195		 * Wait for psi_schedule_poll_work RCU to complete its read-side
  1196		 * critical section before destroying the trigger and optionally the
  1197		 * poll_task.
  1198		 */
  1199		synchronize_rcu();
  1200		/*
  1201		 * Stop kthread 'psimon' after releasing trigger_lock to prevent a
  1202		 * deadlock while waiting for psi_poll_work to acquire trigger_lock
  1203		 */
  1204		if (task_to_destroy) {
  1205			/*
  1206			 * After the RCU grace period has expired, the worker
  1207			 * can no longer be found through group->poll_task.
  1208			 */
  1209			kthread_stop(task_to_destroy);
  1210		}
  1211		kfree(t);
  1212	}
  1213	

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