From: Gentoo CachyOS overlay
Subject: [PATCH] adapt scheduler to CachyOS 6.18.55

Preserve the PID reference fix and scope-based scheduler locking. Guard the
new DEADLINE PI helper with the rest of the fair-scheduler-only helpers.
Upstream: kernel-patches@a8efcb97a509c3d36f839451dacb896ab48581c5/6.18/sched/0001-prjc-cachy.patch
Apply to a copy of the pinned upstream patch, not the kernel tree.

--- a/prjc.patch
+++ b/prjc.patch
@@ -715,8 +715,8 @@
  	write_sequnlock(&sig->stats_lock);
 @@ -291,8 +291,8 @@ void release_task(struct task_struct *p)
  	write_unlock_irq(&tasklist_lock);
- 	/* @thread_pid can't go away until free_pids() below */
  	proc_flush_pid(thread_pid);
+ 	put_pid(thread_pid);
 -	add_device_randomness(&p->se.sum_exec_runtime,
 -			      sizeof(p->se.sum_exec_runtime));
 +	add_device_randomness((const void*) &tsk_seruntime(p),
@@ -10795,9 +10795,9 @@
 +	__task_access_unlock(p, lock);
 +	raw_spin_unlock_irqrestore(&p->pi_lock, flags);
 +#else
- 	bool queued, running;
  	struct rq *rq;
  	int old_prio;
+ 
 @@ -112,6 +156,7 @@ void set_user_nice(struct task_struct *p, long nice)
  	 * lowered its priority, then reschedule its CPU:
  	 */
@@ -10867,9 +10867,9 @@
  
 +#ifndef CONFIG_SCHED_ALT
 +
- #ifdef CONFIG_UCLAMP_TASK
- 
- static int uclamp_validate(struct task_struct *p,
+ #ifdef CONFIG_RT_MUTEXES
+ static inline void __setscheduler_dl_pi(int newprio, int policy,
+ 			      struct task_struct *p,
 @@ -446,6 +513,7 @@ static inline int uclamp_validate(struct task_struct *p,
  static void __setscheduler_uclamp(struct task_struct *p,
  				  const struct sched_attr *attr) { }
@@ -11065,7 +11065,7 @@
 +	return retval;
 +#else /* !CONFIG_SCHED_ALT */
  	int oldpolicy = -1, policy = attr->sched_policy;
- 	int retval, oldprio, newprio, queued, running;
+ 	int retval, oldprio, newprio;
  	const struct sched_class *prev_class, *next_class;
 @@ -750,6 +974,7 @@ int __sched_setscheduler(struct task_struct *p,
  	if (cpuset_locked)