Merge tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Implement the SCHED_DEADLINE server infrastructure - Daniel Bristot
   de Oliveira's last major contribution to the kernel:

     "SCHED_DEADLINE servers can help fixing starvation issues of low
      priority tasks (e.g., SCHED_OTHER) when higher priority tasks
      monopolize CPU cycles. Today we have RT Throttling; DEADLINE
      servers should be able to replace and improve that."

   (Daniel Bristot de Oliveira, Peter Zijlstra, Joel Fernandes, Youssef
   Esmat, Huang Shijie)

 - Preparatory changes for sched_ext integration:
     - Use set_next_task(.first) where required
     - Fix up set_next_task() implementations
     - Clean up DL server vs. core sched
     - Split up put_prev_task_balance()
     - Rework pick_next_task()
     - Combine the last put_prev_task() and the first set_next_task()
     - Rework dl_server
     - Add put_prev_task(.next)

   (Peter Zijlstra, with a fix by Tejun Heo)

 - Complete the EEVDF transition and refine EEVDF scheduling:
     - Implement delayed dequeue
     - Allow shorter slices to wakeup-preempt
     - Use sched_attr::sched_runtime to set request/slice suggestion
     - Document the new feature flags
     - Remove unused and duplicate-functionality fields
     - Simplify & unify pick_next_task_fair()
     - Misc debuggability enhancements

   (Peter Zijlstra, with fixes/cleanups by Dietmar Eggemann, Valentin
   Schneider and Chuyi Zhou)

 - Initialize the vruntime of a new task when it is first enqueued,
   resulting in significant decrease in latency of newly woken tasks
   (Zhang Qiao)

 - Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
   (K Prateek Nayak, Peter Zijlstra)

 - Clean up and clarify the usage of Clean up usage of rt_task()
   (Qais Yousef)

 - Preempt SCHED_IDLE entities in strict cgroup hierarchies
   (Tianchen Ding)

 - Clarify the documentation of time units for deadline scheduler
   parameters (Christian Loehle)

 - Remove the HZ_BW chicken-bit feature flag introduced a year ago,
   the original change seems to be working fine (Phil Auld)

 - Misc fixes and cleanups (Chen Yu, Dan Carpenter, Huang Shijie,
   Peilin He, Qais Yousefm and Vincent Guittot)

* tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
  sched/cpufreq: Use NSEC_PER_MSEC for deadline task
  cpufreq/cppc: Use NSEC_PER_MSEC for deadline task
  sched/deadline: Clarify nanoseconds in uapi
  sched/deadline: Convert schedtool example to chrt
  sched/debug: Fix the runnable tasks output
  sched: Fix sched_delayed vs sched_core
  kernel/sched: Fix util_est accounting for DELAY_DEQUEUE
  kthread: Fix task state in kthread worker if being frozen
  sched/pelt: Use rq_clock_task() for hw_pressure
  sched/fair: Move effective_cpu_util() and effective_cpu_util() in fair.c
  sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
  sched: Add put_prev_task(.next)
  sched: Rework dl_server
  sched: Combine the last put_prev_task() and the first set_next_task()
  sched: Rework pick_next_task()
  sched: Split up put_prev_task_balance()
  sched: Clean up DL server vs core sched
  sched: Fixup set_next_task() implementations
  sched: Use set_next_task(.first) where required
  sched/fair: Properly deactivate sched_delayed task upon class change
  ...

include/linux/ioprio.h

@@ -40,7 +40,7 @@ static inline int task_nice_ioclass(struct task_struct *task)
 {
 	if (task->policy == SCHED_IDLE)
 		return IOPRIO_CLASS_IDLE;
-	else if (task_is_realtime(task))
+	else if (rt_or_dl_task_policy(task))
 		return IOPRIO_CLASS_RT;
 	else
 		return IOPRIO_CLASS_BE;

include/linux/sched.h

@@ -149,8 +149,9 @@ struct user_event_mm;
  * Special states are those that do not use the normal wait-loop pattern. See
  * the comment with set_special_state().
  */
-#define is_special_task_state(state)				\
-	((state) & (__TASK_STOPPED | __TASK_TRACED | TASK_PARKED | TASK_DEAD))
+#define is_special_task_state(state)					\
+	((state) & (__TASK_STOPPED | __TASK_TRACED | TASK_PARKED |	\
+		    TASK_DEAD | TASK_FROZEN))
 
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
 # define debug_normal_state_change(state_value)				\
@@ -541,9 +542,14 @@ struct sched_entity {
 	struct rb_node			run_node;
 	u64				deadline;
 	u64				min_vruntime;
+	u64				min_slice;
 
 	struct list_head		group_node;
-	unsigned int			on_rq;
+	unsigned char			on_rq;
+	unsigned char			sched_delayed;
+	unsigned char			rel_deadline;
+	unsigned char			custom_slice;
+					/* hole */
 
 	u64				exec_start;
 	u64				sum_exec_runtime;
@@ -639,12 +645,26 @@ struct sched_dl_entity {
 	 *
 	 * @dl_overrun tells if the task asked to be informed about runtime
 	 * overruns.
+	 *
+	 * @dl_server tells if this is a server entity.
+	 *
+	 * @dl_defer tells if this is a deferred or regular server. For
+	 * now only defer server exists.
+	 *
+	 * @dl_defer_armed tells if the deferrable server is waiting
+	 * for the replenishment timer to activate it.
+	 *
+	 * @dl_defer_running tells if the deferrable server is actually
+	 * running, skipping the defer phase.
 	 */
 	unsigned int			dl_throttled      : 1;
 	unsigned int			dl_yielded        : 1;
 	unsigned int			dl_non_contending : 1;
 	unsigned int			dl_overrun	  : 1;
 	unsigned int			dl_server         : 1;
+	unsigned int			dl_defer	  : 1;
+	unsigned int			dl_defer_armed	  : 1;
+	unsigned int			dl_defer_running  : 1;
 
 	/*
 	 * Bandwidth enforcement timer. Each -deadline task has its
@@ -672,7 +692,7 @@ struct sched_dl_entity {
 	 */
 	struct rq			*rq;
 	dl_server_has_tasks_f		server_has_tasks;
-	dl_server_pick_f		server_pick;
+	dl_server_pick_f		server_pick_task;
 
 #ifdef CONFIG_RT_MUTEXES
 	/*

include/linux/sched/deadline.h

@@ -10,16 +10,16 @@
 
 #include <linux/sched.h>
 
-#define MAX_DL_PRIO		0
-
-static inline int dl_prio(int prio)
+static inline bool dl_prio(int prio)
 {
-	if (unlikely(prio < MAX_DL_PRIO))
-		return 1;
-	return 0;
+	return unlikely(prio < MAX_DL_PRIO);
 }
 
-static inline int dl_task(struct task_struct *p)
+/*
+ * Returns true if a task has a priority that belongs to DL class. PI-boosted
+ * tasks will return true. Use dl_policy() to ignore PI-boosted tasks.
+ */
+static inline bool dl_task(struct task_struct *p)
 {
 	return dl_prio(p->prio);
 }

include/linux/sched/prio.h

@@ -14,6 +14,7 @@
  */
 
 #define MAX_RT_PRIO		100
+#define MAX_DL_PRIO		0
 
 #define MAX_PRIO		(MAX_RT_PRIO + NICE_WIDTH)
 #define DEFAULT_PRIO		(MAX_RT_PRIO + NICE_WIDTH / 2)

include/linux/sched/rt.h

@@ -6,19 +6,40 @@
 
 struct task_struct;
 
-static inline int rt_prio(int prio)
+static inline bool rt_prio(int prio)
 {
-	if (unlikely(prio < MAX_RT_PRIO))
-		return 1;
-	return 0;
+	return unlikely(prio < MAX_RT_PRIO && prio >= MAX_DL_PRIO);
 }
 
-static inline int rt_task(struct task_struct *p)
+static inline bool rt_or_dl_prio(int prio)
+{
+	return unlikely(prio < MAX_RT_PRIO);
+}
+
+/*
+ * Returns true if a task has a priority that belongs to RT class. PI-boosted
+ * tasks will return true. Use rt_policy() to ignore PI-boosted tasks.
+ */
+static inline bool rt_task(struct task_struct *p)
 {
 	return rt_prio(p->prio);
 }
 
-static inline bool task_is_realtime(struct task_struct *tsk)
+/*
+ * Returns true if a task has a priority that belongs to RT or DL classes.
+ * PI-boosted tasks will return true. Use rt_or_dl_task_policy() to ignore
+ * PI-boosted tasks.
+ */
+static inline bool rt_or_dl_task(struct task_struct *p)
+{
+	return rt_or_dl_prio(p->prio);
+}
+
+/*
+ * Returns true if a task has a policy that belongs to RT or DL classes.
+ * PI-boosted tasks will return false.
+ */
+static inline bool rt_or_dl_task_policy(struct task_struct *tsk)
 {
 	int policy = tsk->policy;