[PATCHSET sched_ext/for-6.18] sched_ext: Misc changes

[PATCHSET sched_ext/for-6.18] sched_ext: Misc changes

[Tejun Heo]

A collection of four misc patches.

- Make scx_task_iter a bit easier to use.

- Keep bypass on between enable failure and disable.

- Move types and accessors into ext_internal.h.

- Wrap event percpu allocation in a struct to ease adding more percpu
  fields.

 0001-sched_ext-Make-explicit-scx_task_iter_relock-calls-u.patch
 0002-sched_ext-Keep-bypass-on-between-enable-failure-and-.patch
 0003-sched_ext-Move-internal-type-and-accessor-definition.patch
 0004-sched_ext-Put-event_stats_cpu-in-struct-scx_sched_pc.patch

 kernel/sched/build_policy.c |    1
 kernel/sched/ext.c          | 1097 +-----------------------------------------------------------------
 kernel/sched/ext.h          |   23 -
 kernel/sched/ext_internal.h | 1064 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 1098 insertions(+), 1087 deletions(-)

--
tejun

[PATCH 1/4] sched_ext: Make explicit scx_task_iter_relock() calls unnecessary

[Tejun Heo]

During tasks iteration, the locks can be dropped using
scx_task_iter_unlock() to perform e.g. sleepable allocations. Afterwards,
scx_task_iter_relock() has to be called prior to other iteration operations,
which is error-prone. This can be easily automated by tracking whether
scx_tasks_lock is held in scx_task_iter and re-acquiring when necessary. It
already tracks whether the task's rq is locked after all.

- Add scx_task_iter->list_locked which remembers whether scx_tasks_lock is
  held.

- Rename scx_task_iter->locked to scx_task_iter->locked_task to better
  distinguish it from ->list_locked.

- Replace scx_task_iter_relock() with __scx_task_iter_maybe_relock() which
  is automatically called by scx_task_iter_next() and scx_task_iter_stop().

- Drop explicit scx_task_iter_relock() calls.

The resulting behavior should be equivalent.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c | 43 +++++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 7dedc9a16281..7f799345c899 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -1488,10 +1488,11 @@ struct bpf_iter_scx_dsq {
  */
 struct scx_task_iter {
 	struct sched_ext_entity		cursor;
-	struct task_struct		*locked;
+	struct task_struct		*locked_task;
 	struct rq			*rq;
 	struct rq_flags			rf;
 	u32				cnt;
+	bool				list_locked;
 };
 
 /**
@@ -1519,15 +1520,16 @@ static void scx_task_iter_start(struct scx_task_iter *iter)
 
 	iter->cursor = (struct sched_ext_entity){ .flags = SCX_TASK_CURSOR };
 	list_add(&iter->cursor.tasks_node, &scx_tasks);
-	iter->locked = NULL;
+	iter->locked_task = NULL;
 	iter->cnt = 0;
+	iter->list_locked = true;
 }
 
 static void __scx_task_iter_rq_unlock(struct scx_task_iter *iter)
 {
-	if (iter->locked) {
-		task_rq_unlock(iter->rq, iter->locked, &iter->rf);
-		iter->locked = NULL;
+	if (iter->locked_task) {
+		task_rq_unlock(iter->rq, iter->locked_task, &iter->rf);
+		iter->locked_task = NULL;
 	}
 }
 
@@ -1537,24 +1539,24 @@ static void __scx_task_iter_rq_unlock(struct scx_task_iter *iter)
  *
  * If @iter is in the middle of a locked iteration, it may be locking the rq of
  * the task currently being visited in addition to scx_tasks_lock. Unlock both.
- * This function can be safely called anytime during an iteration.
+ * This function can be safely called anytime during an iteration. The next
+ * iterator operation will automatically restore the necessary locking.
  */
 static void scx_task_iter_unlock(struct scx_task_iter *iter)
 {
 	__scx_task_iter_rq_unlock(iter);
-	spin_unlock_irq(&scx_tasks_lock);
+	if (iter->list_locked) {
+		iter->list_locked = false;
+		spin_unlock_irq(&scx_tasks_lock);
+	}
 }
 
-/**
- * scx_task_iter_relock - Lock scx_tasks_lock released by scx_task_iter_unlock()
- * @iter: iterator to re-lock
- *
- * Re-lock scx_tasks_lock unlocked by scx_task_iter_unlock(). Note that it
- * doesn't re-lock the rq lock. Must be called before other iterator operations.
- */
-static void scx_task_iter_relock(struct scx_task_iter *iter)
+static void __scx_task_iter_maybe_relock(struct scx_task_iter *iter)
 {
-	spin_lock_irq(&scx_tasks_lock);
+	if (!iter->list_locked) {
+		spin_lock_irq(&scx_tasks_lock);
+		iter->list_locked = true;
+	}
 }
 
 /**
@@ -1567,6 +1569,7 @@ static void scx_task_iter_relock(struct scx_task_iter *iter)
  */
 static void scx_task_iter_stop(struct scx_task_iter *iter)
 {
+	__scx_task_iter_maybe_relock(iter);
 	list_del_init(&iter->cursor.tasks_node);
 	scx_task_iter_unlock(iter);
 }
@@ -1584,10 +1587,12 @@ static struct task_struct *scx_task_iter_next(struct scx_task_iter *iter)
 	struct list_head *cursor = &iter->cursor.tasks_node;
 	struct sched_ext_entity *pos;
 
+	__scx_task_iter_maybe_relock(iter);
+
 	if (!(++iter->cnt % SCX_TASK_ITER_BATCH)) {
 		scx_task_iter_unlock(iter);
 		cond_resched();
-		scx_task_iter_relock(iter);
+		__scx_task_iter_maybe_relock(iter);
 	}
 
 	list_for_each_entry(pos, cursor, tasks_node) {
@@ -1650,7 +1655,7 @@ static struct task_struct *scx_task_iter_next_locked(struct scx_task_iter *iter)
 		return NULL;
 
 	iter->rq = task_rq_lock(p, &iter->rf);
-	iter->locked = p;
+	iter->locked_task = p;
 
 	return p;
 }
@@ -5713,7 +5718,6 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 		ret = scx_init_task(p, task_group(p), false);
 		if (ret) {
 			put_task_struct(p);
-			scx_task_iter_relock(&sti);
 			scx_task_iter_stop(&sti);
 			scx_error(sch, "ops.init_task() failed (%d) for %s[%d]",
 				  ret, p->comm, p->pid);
@@ -5723,7 +5727,6 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 		scx_set_task_state(p, SCX_TASK_READY);
 
 		put_task_struct(p);
-		scx_task_iter_relock(&sti);
 	}
 	scx_task_iter_stop(&sti);
 	scx_cgroup_unlock();
-- 
2.51.0

[PATCH 2/4] sched_ext: Keep bypass on between enable failure and scx_disable_workfn()

[Tejun Heo]

scx_enable() turns on the bypass mode while enable is in progress. If
enabling fails, it turns off the bypass mode and then triggers scx_error().
scx_error() will trigger scx_disable_workfn() which will turn on the bypass
mode again and unload the failed scheduler.

This moves the system out of bypass mode between the enable error path and
the disable path, which is unnecessary and can be brittle - e.g. the thread
running scx_enable() may already be on the failed scheduler and can be
switched out before it triggers scx_error() leading to a stall. The watchdog
would eventually kick in, so the situation isn't critical but is still
suboptimal.

There is nothing to be gained by turning off the bypass mode between
scx_enable() failure and scx_disable_workfn(). Keep bypass on.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 7f799345c899..fda2b4e85ee3 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5794,7 +5794,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 err_disable_unlock_all:
 	scx_cgroup_unlock();
 	percpu_up_write(&scx_fork_rwsem);
-	scx_bypass(false);
+	/* we'll soon enter disable path, keep bypass on */
 err_disable:
 	mutex_unlock(&scx_enable_mutex);
 	/*
-- 
2.51.0

[PATCH 3/4] sched_ext: Move internal type and accessor definitions to ext_internal.h

[Tejun Heo]

There currently isn't a place to place SCX-internal types and accessors to
be shared between ext.c and ext_idle.c. Create kernel/sched/ext_internal.h
and move internal type and accessor definitions there. This trims ext.c a
bit and makes future additions easier. Pure code reorganization. No
functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/build_policy.c |    1 +
 kernel/sched/ext.c          | 1034 ----------------------------------
 kernel/sched/ext.h          |   23 -
 kernel/sched/ext_internal.h | 1061 +++++++++++++++++++++++++++++++++++
 4 files changed, 1062 insertions(+), 1057 deletions(-)
 create mode 100644 kernel/sched/ext_internal.h

diff --git a/kernel/sched/build_policy.c b/kernel/sched/build_policy.c
index c4a488e67aa7..755883faf751 100644
--- a/kernel/sched/build_policy.c
+++ b/kernel/sched/build_policy.c
@@ -58,6 +58,7 @@
 #include "deadline.c"
 
 #ifdef CONFIG_SCHED_CLASS_EXT
+# include "ext_internal.h"
 # include "ext.c"
 # include "ext_idle.c"
 #endif
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index fda2b4e85ee3..7e15e852370c 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -9,1040 +9,6 @@
 #include <linux/btf_ids.h>
 #include "ext_idle.h"
 
-#define SCX_OP_IDX(op)		(offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void)))
-
-enum scx_consts {
-	SCX_DSP_DFL_MAX_BATCH		= 32,
-	SCX_DSP_MAX_LOOPS		= 32,
-	SCX_WATCHDOG_MAX_TIMEOUT	= 30 * HZ,
-
-	SCX_EXIT_BT_LEN			= 64,
-	SCX_EXIT_MSG_LEN		= 1024,
-	SCX_EXIT_DUMP_DFL_LEN		= 32768,
-
-	SCX_CPUPERF_ONE			= SCHED_CAPACITY_SCALE,
-
-	/*
-	 * Iterating all tasks may take a while. Periodically drop
-	 * scx_tasks_lock to avoid causing e.g. CSD and RCU stalls.
-	 */
-	SCX_TASK_ITER_BATCH		= 32,
-};
-
-enum scx_exit_kind {
-	SCX_EXIT_NONE,
-	SCX_EXIT_DONE,
-
-	SCX_EXIT_UNREG = 64,	/* user-space initiated unregistration */
-	SCX_EXIT_UNREG_BPF,	/* BPF-initiated unregistration */
-	SCX_EXIT_UNREG_KERN,	/* kernel-initiated unregistration */
-	SCX_EXIT_SYSRQ,		/* requested by 'S' sysrq */
-
-	SCX_EXIT_ERROR = 1024,	/* runtime error, error msg contains details */
-	SCX_EXIT_ERROR_BPF,	/* ERROR but triggered through scx_bpf_error() */
-	SCX_EXIT_ERROR_STALL,	/* watchdog detected stalled runnable tasks */
-};
-
-/*
- * An exit code can be specified when exiting with scx_bpf_exit() or scx_exit(),
- * corresponding to exit_kind UNREG_BPF and UNREG_KERN respectively. The codes
- * are 64bit of the format:
- *
- *   Bits: [63  ..  48 47   ..  32 31 .. 0]
- *         [ SYS ACT ] [ SYS RSN ] [ USR  ]
- *
- *   SYS ACT: System-defined exit actions
- *   SYS RSN: System-defined exit reasons
- *   USR    : User-defined exit codes and reasons
- *
- * Using the above, users may communicate intention and context by ORing system
- * actions and/or system reasons with a user-defined exit code.
- */
-enum scx_exit_code {
-	/* Reasons */
-	SCX_ECODE_RSN_HOTPLUG	= 1LLU << 32,
-
-	/* Actions */
-	SCX_ECODE_ACT_RESTART	= 1LLU << 48,
-};
-
-/*
- * scx_exit_info is passed to ops.exit() to describe why the BPF scheduler is
- * being disabled.
- */
-struct scx_exit_info {
-	/* %SCX_EXIT_* - broad category of the exit reason */
-	enum scx_exit_kind	kind;
-
-	/* exit code if gracefully exiting */
-	s64			exit_code;
-
-	/* textual representation of the above */
-	const char		*reason;
-
-	/* backtrace if exiting due to an error */
-	unsigned long		*bt;
-	u32			bt_len;
-
-	/* informational message */
-	char			*msg;
-
-	/* debug dump */
-	char			*dump;
-};
-
-/* sched_ext_ops.flags */
-enum scx_ops_flags {
-	/*
-	 * Keep built-in idle tracking even if ops.update_idle() is implemented.
-	 */
-	SCX_OPS_KEEP_BUILTIN_IDLE	= 1LLU << 0,
-
-	/*
-	 * By default, if there are no other task to run on the CPU, ext core
-	 * keeps running the current task even after its slice expires. If this
-	 * flag is specified, such tasks are passed to ops.enqueue() with
-	 * %SCX_ENQ_LAST. See the comment above %SCX_ENQ_LAST for more info.
-	 */
-	SCX_OPS_ENQ_LAST		= 1LLU << 1,
-
-	/*
-	 * An exiting task may schedule after PF_EXITING is set. In such cases,
-	 * bpf_task_from_pid() may not be able to find the task and if the BPF
-	 * scheduler depends on pid lookup for dispatching, the task will be
-	 * lost leading to various issues including RCU grace period stalls.
-	 *
-	 * To mask this problem, by default, unhashed tasks are automatically
-	 * dispatched to the local DSQ on enqueue. If the BPF scheduler doesn't
-	 * depend on pid lookups and wants to handle these tasks directly, the
-	 * following flag can be used.
-	 */
-	SCX_OPS_ENQ_EXITING		= 1LLU << 2,
-
-	/*
-	 * If set, only tasks with policy set to SCHED_EXT are attached to
-	 * sched_ext. If clear, SCHED_NORMAL tasks are also included.
-	 */
-	SCX_OPS_SWITCH_PARTIAL		= 1LLU << 3,
-
-	/*
-	 * A migration disabled task can only execute on its current CPU. By
-	 * default, such tasks are automatically put on the CPU's local DSQ with
-	 * the default slice on enqueue. If this ops flag is set, they also go
-	 * through ops.enqueue().
-	 *
-	 * A migration disabled task never invokes ops.select_cpu() as it can
-	 * only select the current CPU. Also, p->cpus_ptr will only contain its
-	 * current CPU while p->nr_cpus_allowed keeps tracking p->user_cpus_ptr
-	 * and thus may disagree with cpumask_weight(p->cpus_ptr).
-	 */
-	SCX_OPS_ENQ_MIGRATION_DISABLED	= 1LLU << 4,
-
-	/*
-	 * Queued wakeup (ttwu_queue) is a wakeup optimization that invokes
-	 * ops.enqueue() on the ops.select_cpu() selected or the wakee's
-	 * previous CPU via IPI (inter-processor interrupt) to reduce cacheline
-	 * transfers. When this optimization is enabled, ops.select_cpu() is
-	 * skipped in some cases (when racing against the wakee switching out).
-	 * As the BPF scheduler may depend on ops.select_cpu() being invoked
-	 * during wakeups, queued wakeup is disabled by default.
-	 *
-	 * If this ops flag is set, queued wakeup optimization is enabled and
-	 * the BPF scheduler must be able to handle ops.enqueue() invoked on the
-	 * wakee's CPU without preceding ops.select_cpu() even for tasks which
-	 * may be executed on multiple CPUs.
-	 */
-	SCX_OPS_ALLOW_QUEUED_WAKEUP	= 1LLU << 5,
-
-	/*
-	 * If set, enable per-node idle cpumasks. If clear, use a single global
-	 * flat idle cpumask.
-	 */
-	SCX_OPS_BUILTIN_IDLE_PER_NODE	= 1LLU << 6,
-
-	/*
-	 * CPU cgroup support flags
-	 */
-	SCX_OPS_HAS_CGROUP_WEIGHT	= 1LLU << 16,	/* DEPRECATED, will be removed on 6.18 */
-
-	SCX_OPS_ALL_FLAGS		= SCX_OPS_KEEP_BUILTIN_IDLE |
-					  SCX_OPS_ENQ_LAST |
-					  SCX_OPS_ENQ_EXITING |
-					  SCX_OPS_ENQ_MIGRATION_DISABLED |
-					  SCX_OPS_ALLOW_QUEUED_WAKEUP |
-					  SCX_OPS_SWITCH_PARTIAL |
-					  SCX_OPS_BUILTIN_IDLE_PER_NODE |
-					  SCX_OPS_HAS_CGROUP_WEIGHT,
-
-	/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
-	__SCX_OPS_INTERNAL_MASK		= 0xffLLU << 56,
-
-	SCX_OPS_HAS_CPU_PREEMPT		= 1LLU << 56,
-};
-
-/* argument container for ops.init_task() */
-struct scx_init_task_args {
-	/*
-	 * Set if ops.init_task() is being invoked on the fork path, as opposed
-	 * to the scheduler transition path.
-	 */
-	bool			fork;
-#ifdef CONFIG_EXT_GROUP_SCHED
-	/* the cgroup the task is joining */
-	struct cgroup		*cgroup;
-#endif
-};
-
-/* argument container for ops.exit_task() */
-struct scx_exit_task_args {
-	/* Whether the task exited before running on sched_ext. */
-	bool cancelled;
-};
-
-/* argument container for ops->cgroup_init() */
-struct scx_cgroup_init_args {
-	/* the weight of the cgroup [1..10000] */
-	u32			weight;
-
-	/* bandwidth control parameters from cpu.max and cpu.max.burst */
-	u64			bw_period_us;
-	u64			bw_quota_us;
-	u64			bw_burst_us;
-};
-
-enum scx_cpu_preempt_reason {
-	/* next task is being scheduled by &sched_class_rt */
-	SCX_CPU_PREEMPT_RT,
-	/* next task is being scheduled by &sched_class_dl */
-	SCX_CPU_PREEMPT_DL,
-	/* next task is being scheduled by &sched_class_stop */
-	SCX_CPU_PREEMPT_STOP,
-	/* unknown reason for SCX being preempted */
-	SCX_CPU_PREEMPT_UNKNOWN,
-};
-
-/*
- * Argument container for ops->cpu_acquire(). Currently empty, but may be
- * expanded in the future.
- */
-struct scx_cpu_acquire_args {};
-
-/* argument container for ops->cpu_release() */
-struct scx_cpu_release_args {
-	/* the reason the CPU was preempted */
-	enum scx_cpu_preempt_reason reason;
-
-	/* the task that's going to be scheduled on the CPU */
-	struct task_struct	*task;
-};
-
-/*
- * Informational context provided to dump operations.
- */
-struct scx_dump_ctx {
-	enum scx_exit_kind	kind;
-	s64			exit_code;
-	const char		*reason;
-	u64			at_ns;
-	u64			at_jiffies;
-};
-
-/**
- * struct sched_ext_ops - Operation table for BPF scheduler implementation
- *
- * A BPF scheduler can implement an arbitrary scheduling policy by
- * implementing and loading operations in this table. Note that a userland
- * scheduling policy can also be implemented using the BPF scheduler
- * as a shim layer.
- */
-struct sched_ext_ops {
-	/**
-	 * @select_cpu: Pick the target CPU for a task which is being woken up
-	 * @p: task being woken up
-	 * @prev_cpu: the cpu @p was on before sleeping
-	 * @wake_flags: SCX_WAKE_*
-	 *
-	 * Decision made here isn't final. @p may be moved to any CPU while it
-	 * is getting dispatched for execution later. However, as @p is not on
-	 * the rq at this point, getting the eventual execution CPU right here
-	 * saves a small bit of overhead down the line.
-	 *
-	 * If an idle CPU is returned, the CPU is kicked and will try to
-	 * dispatch. While an explicit custom mechanism can be added,
-	 * select_cpu() serves as the default way to wake up idle CPUs.
-	 *
-	 * @p may be inserted into a DSQ directly by calling
-	 * scx_bpf_dsq_insert(). If so, the ops.enqueue() will be skipped.
-	 * Directly inserting into %SCX_DSQ_LOCAL will put @p in the local DSQ
-	 * of the CPU returned by this operation.
-	 *
-	 * Note that select_cpu() is never called for tasks that can only run
-	 * on a single CPU or tasks with migration disabled, as they don't have
-	 * the option to select a different CPU. See select_task_rq() for
-	 * details.
-	 */
-	s32 (*select_cpu)(struct task_struct *p, s32 prev_cpu, u64 wake_flags);
-
-	/**
-	 * @enqueue: Enqueue a task on the BPF scheduler
-	 * @p: task being enqueued
-	 * @enq_flags: %SCX_ENQ_*
-	 *
-	 * @p is ready to run. Insert directly into a DSQ by calling
-	 * scx_bpf_dsq_insert() or enqueue on the BPF scheduler. If not directly
-	 * inserted, the bpf scheduler owns @p and if it fails to dispatch @p,
-	 * the task will stall.
-	 *
-	 * If @p was inserted into a DSQ from ops.select_cpu(), this callback is
-	 * skipped.
-	 */
-	void (*enqueue)(struct task_struct *p, u64 enq_flags);
-
-	/**
-	 * @dequeue: Remove a task from the BPF scheduler
-	 * @p: task being dequeued
-	 * @deq_flags: %SCX_DEQ_*
-	 *
-	 * Remove @p from the BPF scheduler. This is usually called to isolate
-	 * the task while updating its scheduling properties (e.g. priority).
-	 *
-	 * The ext core keeps track of whether the BPF side owns a given task or
-	 * not and can gracefully ignore spurious dispatches from BPF side,
-	 * which makes it safe to not implement this method. However, depending
-	 * on the scheduling logic, this can lead to confusing behaviors - e.g.
-	 * scheduling position not being updated across a priority change.
-	 */
-	void (*dequeue)(struct task_struct *p, u64 deq_flags);
-
-	/**
-	 * @dispatch: Dispatch tasks from the BPF scheduler and/or user DSQs
-	 * @cpu: CPU to dispatch tasks for
-	 * @prev: previous task being switched out
-	 *
-	 * Called when a CPU's local dsq is empty. The operation should dispatch
-	 * one or more tasks from the BPF scheduler into the DSQs using
-	 * scx_bpf_dsq_insert() and/or move from user DSQs into the local DSQ
-	 * using scx_bpf_dsq_move_to_local().
-	 *
-	 * The maximum number of times scx_bpf_dsq_insert() can be called
-	 * without an intervening scx_bpf_dsq_move_to_local() is specified by
-	 * ops.dispatch_max_batch. See the comments on top of the two functions
-	 * for more details.
-	 *
-	 * When not %NULL, @prev is an SCX task with its slice depleted. If
-	 * @prev is still runnable as indicated by set %SCX_TASK_QUEUED in
-	 * @prev->scx.flags, it is not enqueued yet and will be enqueued after
-	 * ops.dispatch() returns. To keep executing @prev, return without
-	 * dispatching or moving any tasks. Also see %SCX_OPS_ENQ_LAST.
-	 */
-	void (*dispatch)(s32 cpu, struct task_struct *prev);
-
-	/**
-	 * @tick: Periodic tick
-	 * @p: task running currently
-	 *
-	 * This operation is called every 1/HZ seconds on CPUs which are
-	 * executing an SCX task. Setting @p->scx.slice to 0 will trigger an
-	 * immediate dispatch cycle on the CPU.
-	 */
-	void (*tick)(struct task_struct *p);
-
-	/**
-	 * @runnable: A task is becoming runnable on its associated CPU
-	 * @p: task becoming runnable
-	 * @enq_flags: %SCX_ENQ_*
-	 *
-	 * This and the following three functions can be used to track a task's
-	 * execution state transitions. A task becomes ->runnable() on a CPU,
-	 * and then goes through one or more ->running() and ->stopping() pairs
-	 * as it runs on the CPU, and eventually becomes ->quiescent() when it's
-	 * done running on the CPU.
-	 *
-	 * @p is becoming runnable on the CPU because it's
-	 *
-	 * - waking up (%SCX_ENQ_WAKEUP)
-	 * - being moved from another CPU
-	 * - being restored after temporarily taken off the queue for an
-	 *   attribute change.
-	 *
-	 * This and ->enqueue() are related but not coupled. This operation
-	 * notifies @p's state transition and may not be followed by ->enqueue()
-	 * e.g. when @p is being dispatched to a remote CPU, or when @p is
-	 * being enqueued on a CPU experiencing a hotplug event. Likewise, a
-	 * task may be ->enqueue()'d without being preceded by this operation
-	 * e.g. after exhausting its slice.
-	 */
-	void (*runnable)(struct task_struct *p, u64 enq_flags);
-
-	/**
-	 * @running: A task is starting to run on its associated CPU
-	 * @p: task starting to run
-	 *
-	 * Note that this callback may be called from a CPU other than the
-	 * one the task is going to run on. This can happen when a task
-	 * property is changed (i.e., affinity), since scx_next_task_scx(),
-	 * which triggers this callback, may run on a CPU different from
-	 * the task's assigned CPU.
-	 *
-	 * Therefore, always use scx_bpf_task_cpu(@p) to determine the
-	 * target CPU the task is going to use.
-	 *
-	 * See ->runnable() for explanation on the task state notifiers.
-	 */
-	void (*running)(struct task_struct *p);
-
-	/**
-	 * @stopping: A task is stopping execution
-	 * @p: task stopping to run
-	 * @runnable: is task @p still runnable?
-	 *
-	 * Note that this callback may be called from a CPU other than the
-	 * one the task was running on. This can happen when a task
-	 * property is changed (i.e., affinity), since dequeue_task_scx(),
-	 * which triggers this callback, may run on a CPU different from
-	 * the task's assigned CPU.
-	 *
-	 * Therefore, always use scx_bpf_task_cpu(@p) to retrieve the CPU
-	 * the task was running on.
-	 *
-	 * See ->runnable() for explanation on the task state notifiers. If
-	 * !@runnable, ->quiescent() will be invoked after this operation
-	 * returns.
-	 */
-	void (*stopping)(struct task_struct *p, bool runnable);
-
-	/**
-	 * @quiescent: A task is becoming not runnable on its associated CPU
-	 * @p: task becoming not runnable
-	 * @deq_flags: %SCX_DEQ_*
-	 *
-	 * See ->runnable() for explanation on the task state notifiers.
-	 *
-	 * @p is becoming quiescent on the CPU because it's
-	 *
-	 * - sleeping (%SCX_DEQ_SLEEP)
-	 * - being moved to another CPU
-	 * - being temporarily taken off the queue for an attribute change
-	 *   (%SCX_DEQ_SAVE)
-	 *
-	 * This and ->dequeue() are related but not coupled. This operation
-	 * notifies @p's state transition and may not be preceded by ->dequeue()
-	 * e.g. when @p is being dispatched to a remote CPU.
-	 */
-	void (*quiescent)(struct task_struct *p, u64 deq_flags);
-
-	/**
-	 * @yield: Yield CPU
-	 * @from: yielding task
-	 * @to: optional yield target task
-	 *
-	 * If @to is NULL, @from is yielding the CPU to other runnable tasks.
-	 * The BPF scheduler should ensure that other available tasks are
-	 * dispatched before the yielding task. Return value is ignored in this
-	 * case.
-	 *
-	 * If @to is not-NULL, @from wants to yield the CPU to @to. If the bpf
-	 * scheduler can implement the request, return %true; otherwise, %false.
-	 */
-	bool (*yield)(struct task_struct *from, struct task_struct *to);
-
-	/**
-	 * @core_sched_before: Task ordering for core-sched
-	 * @a: task A
-	 * @b: task B
-	 *
-	 * Used by core-sched to determine the ordering between two tasks. See
-	 * Documentation/admin-guide/hw-vuln/core-scheduling.rst for details on
-	 * core-sched.
-	 *
-	 * Both @a and @b are runnable and may or may not currently be queued on
-	 * the BPF scheduler. Should return %true if @a should run before @b.
-	 * %false if there's no required ordering or @b should run before @a.
-	 *
-	 * If not specified, the default is ordering them according to when they
-	 * became runnable.
-	 */
-	bool (*core_sched_before)(struct task_struct *a, struct task_struct *b);
-
-	/**
-	 * @set_weight: Set task weight
-	 * @p: task to set weight for
-	 * @weight: new weight [1..10000]
-	 *
-	 * Update @p's weight to @weight.
-	 */
-	void (*set_weight)(struct task_struct *p, u32 weight);
-
-	/**
-	 * @set_cpumask: Set CPU affinity
-	 * @p: task to set CPU affinity for
-	 * @cpumask: cpumask of cpus that @p can run on
-	 *
-	 * Update @p's CPU affinity to @cpumask.
-	 */
-	void (*set_cpumask)(struct task_struct *p,
-			    const struct cpumask *cpumask);
-
-	/**
-	 * @update_idle: Update the idle state of a CPU
-	 * @cpu: CPU to update the idle state for
-	 * @idle: whether entering or exiting the idle state
-	 *
-	 * This operation is called when @rq's CPU goes or leaves the idle
-	 * state. By default, implementing this operation disables the built-in
-	 * idle CPU tracking and the following helpers become unavailable:
-	 *
-	 * - scx_bpf_select_cpu_dfl()
-	 * - scx_bpf_select_cpu_and()
-	 * - scx_bpf_test_and_clear_cpu_idle()
-	 * - scx_bpf_pick_idle_cpu()
-	 *
-	 * The user also must implement ops.select_cpu() as the default
-	 * implementation relies on scx_bpf_select_cpu_dfl().
-	 *
-	 * Specify the %SCX_OPS_KEEP_BUILTIN_IDLE flag to keep the built-in idle
-	 * tracking.
-	 */
-	void (*update_idle)(s32 cpu, bool idle);
-
-	/**
-	 * @cpu_acquire: A CPU is becoming available to the BPF scheduler
-	 * @cpu: The CPU being acquired by the BPF scheduler.
-	 * @args: Acquire arguments, see the struct definition.
-	 *
-	 * A CPU that was previously released from the BPF scheduler is now once
-	 * again under its control.
-	 */
-	void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
-
-	/**
-	 * @cpu_release: A CPU is taken away from the BPF scheduler
-	 * @cpu: The CPU being released by the BPF scheduler.
-	 * @args: Release arguments, see the struct definition.
-	 *
-	 * The specified CPU is no longer under the control of the BPF
-	 * scheduler. This could be because it was preempted by a higher
-	 * priority sched_class, though there may be other reasons as well. The
-	 * caller should consult @args->reason to determine the cause.
-	 */
-	void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
-
-	/**
-	 * @init_task: Initialize a task to run in a BPF scheduler
-	 * @p: task to initialize for BPF scheduling
-	 * @args: init arguments, see the struct definition
-	 *
-	 * Either we're loading a BPF scheduler or a new task is being forked.
-	 * Initialize @p for BPF scheduling. This operation may block and can
-	 * be used for allocations, and is called exactly once for a task.
-	 *
-	 * Return 0 for success, -errno for failure. An error return while
-	 * loading will abort loading of the BPF scheduler. During a fork, it
-	 * will abort that specific fork.
-	 */
-	s32 (*init_task)(struct task_struct *p, struct scx_init_task_args *args);
-
-	/**
-	 * @exit_task: Exit a previously-running task from the system
-	 * @p: task to exit
-	 * @args: exit arguments, see the struct definition
-	 *
-	 * @p is exiting or the BPF scheduler is being unloaded. Perform any
-	 * necessary cleanup for @p.
-	 */
-	void (*exit_task)(struct task_struct *p, struct scx_exit_task_args *args);
-
-	/**
-	 * @enable: Enable BPF scheduling for a task
-	 * @p: task to enable BPF scheduling for
-	 *
-	 * Enable @p for BPF scheduling. enable() is called on @p any time it
-	 * enters SCX, and is always paired with a matching disable().
-	 */
-	void (*enable)(struct task_struct *p);
-
-	/**
-	 * @disable: Disable BPF scheduling for a task
-	 * @p: task to disable BPF scheduling for
-	 *
-	 * @p is exiting, leaving SCX or the BPF scheduler is being unloaded.
-	 * Disable BPF scheduling for @p. A disable() call is always matched
-	 * with a prior enable() call.
-	 */
-	void (*disable)(struct task_struct *p);
-
-	/**
-	 * @dump: Dump BPF scheduler state on error
-	 * @ctx: debug dump context
-	 *
-	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump.
-	 */
-	void (*dump)(struct scx_dump_ctx *ctx);
-
-	/**
-	 * @dump_cpu: Dump BPF scheduler state for a CPU on error
-	 * @ctx: debug dump context
-	 * @cpu: CPU to generate debug dump for
-	 * @idle: @cpu is currently idle without any runnable tasks
-	 *
-	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
-	 * @cpu. If @idle is %true and this operation doesn't produce any
-	 * output, @cpu is skipped for dump.
-	 */
-	void (*dump_cpu)(struct scx_dump_ctx *ctx, s32 cpu, bool idle);
-
-	/**
-	 * @dump_task: Dump BPF scheduler state for a runnable task on error
-	 * @ctx: debug dump context
-	 * @p: runnable task to generate debug dump for
-	 *
-	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
-	 * @p.
-	 */
-	void (*dump_task)(struct scx_dump_ctx *ctx, struct task_struct *p);
-
-#ifdef CONFIG_EXT_GROUP_SCHED
-	/**
-	 * @cgroup_init: Initialize a cgroup
-	 * @cgrp: cgroup being initialized
-	 * @args: init arguments, see the struct definition
-	 *
-	 * Either the BPF scheduler is being loaded or @cgrp created, initialize
-	 * @cgrp for sched_ext. This operation may block.
-	 *
-	 * Return 0 for success, -errno for failure. An error return while
-	 * loading will abort loading of the BPF scheduler. During cgroup
-	 * creation, it will abort the specific cgroup creation.
-	 */
-	s32 (*cgroup_init)(struct cgroup *cgrp,
-			   struct scx_cgroup_init_args *args);
-
-	/**
-	 * @cgroup_exit: Exit a cgroup
-	 * @cgrp: cgroup being exited
-	 *
-	 * Either the BPF scheduler is being unloaded or @cgrp destroyed, exit
-	 * @cgrp for sched_ext. This operation my block.
-	 */
-	void (*cgroup_exit)(struct cgroup *cgrp);
-
-	/**
-	 * @cgroup_prep_move: Prepare a task to be moved to a different cgroup
-	 * @p: task being moved
-	 * @from: cgroup @p is being moved from
-	 * @to: cgroup @p is being moved to
-	 *
-	 * Prepare @p for move from cgroup @from to @to. This operation may
-	 * block and can be used for allocations.
-	 *
-	 * Return 0 for success, -errno for failure. An error return aborts the
-	 * migration.
-	 */
-	s32 (*cgroup_prep_move)(struct task_struct *p,
-				struct cgroup *from, struct cgroup *to);
-
-	/**
-	 * @cgroup_move: Commit cgroup move
-	 * @p: task being moved
-	 * @from: cgroup @p is being moved from
-	 * @to: cgroup @p is being moved to
-	 *
-	 * Commit the move. @p is dequeued during this operation.
-	 */
-	void (*cgroup_move)(struct task_struct *p,
-			    struct cgroup *from, struct cgroup *to);
-
-	/**
-	 * @cgroup_cancel_move: Cancel cgroup move
-	 * @p: task whose cgroup move is being canceled
-	 * @from: cgroup @p was being moved from
-	 * @to: cgroup @p was being moved to
-	 *
-	 * @p was cgroup_prep_move()'d but failed before reaching cgroup_move().
-	 * Undo the preparation.
-	 */
-	void (*cgroup_cancel_move)(struct task_struct *p,
-				   struct cgroup *from, struct cgroup *to);
-
-	/**
-	 * @cgroup_set_weight: A cgroup's weight is being changed
-	 * @cgrp: cgroup whose weight is being updated
-	 * @weight: new weight [1..10000]
-	 *
-	 * Update @cgrp's weight to @weight.
-	 */
-	void (*cgroup_set_weight)(struct cgroup *cgrp, u32 weight);
-
-	/**
-	 * @cgroup_set_bandwidth: A cgroup's bandwidth is being changed
-	 * @cgrp: cgroup whose bandwidth is being updated
-	 * @period_us: bandwidth control period
-	 * @quota_us: bandwidth control quota
-	 * @burst_us: bandwidth control burst
-	 *
-	 * Update @cgrp's bandwidth control parameters. This is from the cpu.max
-	 * cgroup interface.
-	 *
-	 * @quota_us / @period_us determines the CPU bandwidth @cgrp is entitled
-	 * to. For example, if @period_us is 1_000_000 and @quota_us is
-	 * 2_500_000. @cgrp is entitled to 2.5 CPUs. @burst_us can be
-	 * interpreted in the same fashion and specifies how much @cgrp can
-	 * burst temporarily. The specific control mechanism and thus the
-	 * interpretation of @period_us and burstiness is upto to the BPF
-	 * scheduler.
-	 */
-	void (*cgroup_set_bandwidth)(struct cgroup *cgrp,
-				     u64 period_us, u64 quota_us, u64 burst_us);
-
-#endif	/* CONFIG_EXT_GROUP_SCHED */
-
-	/*
-	 * All online ops must come before ops.cpu_online().
-	 */
-
-	/**
-	 * @cpu_online: A CPU became online
-	 * @cpu: CPU which just came up
-	 *
-	 * @cpu just came online. @cpu will not call ops.enqueue() or
-	 * ops.dispatch(), nor run tasks associated with other CPUs beforehand.
-	 */
-	void (*cpu_online)(s32 cpu);
-
-	/**
-	 * @cpu_offline: A CPU is going offline
-	 * @cpu: CPU which is going offline
-	 *
-	 * @cpu is going offline. @cpu will not call ops.enqueue() or
-	 * ops.dispatch(), nor run tasks associated with other CPUs afterwards.
-	 */
-	void (*cpu_offline)(s32 cpu);
-
-	/*
-	 * All CPU hotplug ops must come before ops.init().
-	 */
-
-	/**
-	 * @init: Initialize the BPF scheduler
-	 */
-	s32 (*init)(void);
-
-	/**
-	 * @exit: Clean up after the BPF scheduler
-	 * @info: Exit info
-	 *
-	 * ops.exit() is also called on ops.init() failure, which is a bit
-	 * unusual. This is to allow rich reporting through @info on how
-	 * ops.init() failed.
-	 */
-	void (*exit)(struct scx_exit_info *info);
-
-	/**
-	 * @dispatch_max_batch: Max nr of tasks that dispatch() can dispatch
-	 */
-	u32 dispatch_max_batch;
-
-	/**
-	 * @flags: %SCX_OPS_* flags
-	 */
-	u64 flags;
-
-	/**
-	 * @timeout_ms: The maximum amount of time, in milliseconds, that a
-	 * runnable task should be able to wait before being scheduled. The
-	 * maximum timeout may not exceed the default timeout of 30 seconds.
-	 *
-	 * Defaults to the maximum allowed timeout value of 30 seconds.
-	 */
-	u32 timeout_ms;
-
-	/**
-	 * @exit_dump_len: scx_exit_info.dump buffer length. If 0, the default
-	 * value of 32768 is used.
-	 */
-	u32 exit_dump_len;
-
-	/**
-	 * @hotplug_seq: A sequence number that may be set by the scheduler to
-	 * detect when a hotplug event has occurred during the loading process.
-	 * If 0, no detection occurs. Otherwise, the scheduler will fail to
-	 * load if the sequence number does not match @scx_hotplug_seq on the
-	 * enable path.
-	 */
-	u64 hotplug_seq;
-
-	/**
-	 * @name: BPF scheduler's name
-	 *
-	 * Must be a non-zero valid BPF object name including only isalnum(),
-	 * '_' and '.' chars. Shows up in kernel.sched_ext_ops sysctl while the
-	 * BPF scheduler is enabled.
-	 */
-	char name[SCX_OPS_NAME_LEN];
-
-	/* internal use only, must be NULL */
-	void *priv;
-};
-
-enum scx_opi {
-	SCX_OPI_BEGIN			= 0,
-	SCX_OPI_NORMAL_BEGIN		= 0,
-	SCX_OPI_NORMAL_END		= SCX_OP_IDX(cpu_online),
-	SCX_OPI_CPU_HOTPLUG_BEGIN	= SCX_OP_IDX(cpu_online),
-	SCX_OPI_CPU_HOTPLUG_END		= SCX_OP_IDX(init),
-	SCX_OPI_END			= SCX_OP_IDX(init),
-};
-
-/*
- * Collection of event counters. Event types are placed in descending order.
- */
-struct scx_event_stats {
-	/*
-	 * If ops.select_cpu() returns a CPU which can't be used by the task,
-	 * the core scheduler code silently picks a fallback CPU.
-	 */
-	s64		SCX_EV_SELECT_CPU_FALLBACK;
-
-	/*
-	 * When dispatching to a local DSQ, the CPU may have gone offline in
-	 * the meantime. In this case, the task is bounced to the global DSQ.
-	 */
-	s64		SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE;
-
-	/*
-	 * If SCX_OPS_ENQ_LAST is not set, the number of times that a task
-	 * continued to run because there were no other tasks on the CPU.
-	 */
-	s64		SCX_EV_DISPATCH_KEEP_LAST;
-
-	/*
-	 * If SCX_OPS_ENQ_EXITING is not set, the number of times that a task
-	 * is dispatched to a local DSQ when exiting.
-	 */
-	s64		SCX_EV_ENQ_SKIP_EXITING;
-
-	/*
-	 * If SCX_OPS_ENQ_MIGRATION_DISABLED is not set, the number of times a
-	 * migration disabled task skips ops.enqueue() and is dispatched to its
-	 * local DSQ.
-	 */
-	s64		SCX_EV_ENQ_SKIP_MIGRATION_DISABLED;
-
-	/*
-	 * Total number of times a task's time slice was refilled with the
-	 * default value (SCX_SLICE_DFL).
-	 */
-	s64		SCX_EV_REFILL_SLICE_DFL;
-
-	/*
-	 * The total duration of bypass modes in nanoseconds.
-	 */
-	s64		SCX_EV_BYPASS_DURATION;
-
-	/*
-	 * The number of tasks dispatched in the bypassing mode.
-	 */
-	s64		SCX_EV_BYPASS_DISPATCH;
-
-	/*
-	 * The number of times the bypassing mode has been activated.
-	 */
-	s64		SCX_EV_BYPASS_ACTIVATE;
-};
-
-struct scx_sched {
-	struct sched_ext_ops	ops;
-	DECLARE_BITMAP(has_op, SCX_OPI_END);
-
-	/*
-	 * Dispatch queues.
-	 *
-	 * The global DSQ (%SCX_DSQ_GLOBAL) is split per-node for scalability.
-	 * This is to avoid live-locking in bypass mode where all tasks are
-	 * dispatched to %SCX_DSQ_GLOBAL and all CPUs consume from it. If
-	 * per-node split isn't sufficient, it can be further split.
-	 */
-	struct rhashtable	dsq_hash;
-	struct scx_dispatch_q	**global_dsqs;
-
-	/*
-	 * The event counters are in a per-CPU variable to minimize the
-	 * accounting overhead. A system-wide view on the event counter is
-	 * constructed when requested by scx_bpf_events().
-	 */
-	struct scx_event_stats __percpu *event_stats_cpu;
-
-	bool			warned_zero_slice;
-
-	atomic_t		exit_kind;
-	struct scx_exit_info	*exit_info;
-
-	struct kobject		kobj;
-
-	struct kthread_worker	*helper;
-	struct irq_work		error_irq_work;
-	struct kthread_work	disable_work;
-	struct rcu_work		rcu_work;
-};
-
-enum scx_wake_flags {
-	/* expose select WF_* flags as enums */
-	SCX_WAKE_FORK		= WF_FORK,
-	SCX_WAKE_TTWU		= WF_TTWU,
-	SCX_WAKE_SYNC		= WF_SYNC,
-};
-
-enum scx_enq_flags {
-	/* expose select ENQUEUE_* flags as enums */
-	SCX_ENQ_WAKEUP		= ENQUEUE_WAKEUP,
-	SCX_ENQ_HEAD		= ENQUEUE_HEAD,
-	SCX_ENQ_CPU_SELECTED	= ENQUEUE_RQ_SELECTED,
-
-	/* high 32bits are SCX specific */
-
-	/*
-	 * Set the following to trigger preemption when calling
-	 * scx_bpf_dsq_insert() with a local dsq as the target. The slice of the
-	 * current task is cleared to zero and the CPU is kicked into the
-	 * scheduling path. Implies %SCX_ENQ_HEAD.
-	 */
-	SCX_ENQ_PREEMPT		= 1LLU << 32,
-
-	/*
-	 * The task being enqueued was previously enqueued on the current CPU's
-	 * %SCX_DSQ_LOCAL, but was removed from it in a call to the
-	 * scx_bpf_reenqueue_local() kfunc. If scx_bpf_reenqueue_local() was
-	 * invoked in a ->cpu_release() callback, and the task is again
-	 * dispatched back to %SCX_LOCAL_DSQ by this current ->enqueue(), the
-	 * task will not be scheduled on the CPU until at least the next invocation
-	 * of the ->cpu_acquire() callback.
-	 */
-	SCX_ENQ_REENQ		= 1LLU << 40,
-
-	/*
-	 * The task being enqueued is the only task available for the cpu. By
-	 * default, ext core keeps executing such tasks but when
-	 * %SCX_OPS_ENQ_LAST is specified, they're ops.enqueue()'d with the
-	 * %SCX_ENQ_LAST flag set.
-	 *
-	 * The BPF scheduler is responsible for triggering a follow-up
-	 * scheduling event. Otherwise, Execution may stall.
-	 */
-	SCX_ENQ_LAST		= 1LLU << 41,
-
-	/* high 8 bits are internal */
-	__SCX_ENQ_INTERNAL_MASK	= 0xffLLU << 56,
-
-	SCX_ENQ_CLEAR_OPSS	= 1LLU << 56,
-	SCX_ENQ_DSQ_PRIQ	= 1LLU << 57,
-};
-
-enum scx_deq_flags {
-	/* expose select DEQUEUE_* flags as enums */
-	SCX_DEQ_SLEEP		= DEQUEUE_SLEEP,
-
-	/* high 32bits are SCX specific */
-
-	/*
-	 * The generic core-sched layer decided to execute the task even though
-	 * it hasn't been dispatched yet. Dequeue from the BPF side.
-	 */
-	SCX_DEQ_CORE_SCHED_EXEC	= 1LLU << 32,
-};
-
-enum scx_pick_idle_cpu_flags {
-	SCX_PICK_IDLE_CORE	= 1LLU << 0,	/* pick a CPU whose SMT siblings are also idle */
-	SCX_PICK_IDLE_IN_NODE	= 1LLU << 1,	/* pick a CPU in the same target NUMA node */
-};
-
-enum scx_kick_flags {
-	/*
-	 * Kick the target CPU if idle. Guarantees that the target CPU goes
-	 * through at least one full scheduling cycle before going idle. If the
-	 * target CPU can be determined to be currently not idle and going to go
-	 * through a scheduling cycle before going idle, noop.
-	 */
-	SCX_KICK_IDLE		= 1LLU << 0,
-
-	/*
-	 * Preempt the current task and execute the dispatch path. If the
-	 * current task of the target CPU is an SCX task, its ->scx.slice is
-	 * cleared to zero before the scheduling path is invoked so that the
-	 * task expires and the dispatch path is invoked.
-	 */
-	SCX_KICK_PREEMPT	= 1LLU << 1,
-
-	/*
-	 * Wait for the CPU to be rescheduled. The scx_bpf_kick_cpu() call will
-	 * return after the target CPU finishes picking the next task.
-	 */
-	SCX_KICK_WAIT		= 1LLU << 2,
-};
-
-enum scx_tg_flags {
-	SCX_TG_ONLINE		= 1U << 0,
-	SCX_TG_INITED		= 1U << 1,
-};
-
-enum scx_enable_state {
-	SCX_ENABLING,
-	SCX_ENABLED,
-	SCX_DISABLING,
-	SCX_DISABLED,
-};
-
-static const char *scx_enable_state_str[] = {
-	[SCX_ENABLING]		= "enabling",
-	[SCX_ENABLED]		= "enabled",
-	[SCX_DISABLING]		= "disabling",
-	[SCX_DISABLED]		= "disabled",
-};
-
-/*
- * sched_ext_entity->ops_state
- *
- * Used to track the task ownership between the SCX core and the BPF scheduler.
- * State transitions look as follows:
- *
- * NONE -> QUEUEING -> QUEUED -> DISPATCHING
- *   ^              |                 |
- *   |              v                 v
- *   \-------------------------------/
- *
- * QUEUEING and DISPATCHING states can be waited upon. See wait_ops_state() call
- * sites for explanations on the conditions being waited upon and why they are
- * safe. Transitions out of them into NONE or QUEUED must store_release and the
- * waiters should load_acquire.
- *
- * Tracking scx_ops_state enables sched_ext core to reliably determine whether
- * any given task can be dispatched by the BPF scheduler at all times and thus
- * relaxes the requirements on the BPF scheduler. This allows the BPF scheduler
- * to try to dispatch any task anytime regardless of its state as the SCX core
- * can safely reject invalid dispatches.
- */
-enum scx_ops_state {
-	SCX_OPSS_NONE,		/* owned by the SCX core */
-	SCX_OPSS_QUEUEING,	/* in transit to the BPF scheduler */
-	SCX_OPSS_QUEUED,	/* owned by the BPF scheduler */
-	SCX_OPSS_DISPATCHING,	/* in transit back to the SCX core */
-
-	/*
-	 * QSEQ brands each QUEUED instance so that, when dispatch races
-	 * dequeue/requeue, the dispatcher can tell whether it still has a claim
-	 * on the task being dispatched.
-	 *
-	 * As some 32bit archs can't do 64bit store_release/load_acquire,
-	 * p->scx.ops_state is atomic_long_t which leaves 30 bits for QSEQ on
-	 * 32bit machines. The dispatch race window QSEQ protects is very narrow
-	 * and runs with IRQ disabled. 30 bits should be sufficient.
-	 */
-	SCX_OPSS_QSEQ_SHIFT	= 2,
-};
-
-/* Use macros to ensure that the type is unsigned long for the masks */
-#define SCX_OPSS_STATE_MASK	((1LU << SCX_OPSS_QSEQ_SHIFT) - 1)
-#define SCX_OPSS_QSEQ_MASK	(~SCX_OPSS_STATE_MASK)
-
 /*
  * NOTE: sched_ext is in the process of growing multiple scheduler support and
  * scx_root usage is in a transitional state. Naked dereferences are safe if the
diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h
index 292bb41a242e..33858607bc97 100644
--- a/kernel/sched/ext.h
+++ b/kernel/sched/ext.h
@@ -8,29 +8,6 @@
  */
 #ifdef CONFIG_SCHED_CLASS_EXT
 
-static inline bool scx_kf_allowed_if_unlocked(void)
-{
-	return !current->scx.kf_mask;
-}
-
-static inline bool scx_rq_bypassing(struct rq *rq)
-{
-	return unlikely(rq->scx.flags & SCX_RQ_BYPASSING);
-}
-
-DECLARE_STATIC_KEY_FALSE(scx_ops_allow_queued_wakeup);
-
-DECLARE_PER_CPU(struct rq *, scx_locked_rq_state);
-
-/*
- * Return the rq currently locked from an scx callback, or NULL if no rq is
- * locked.
- */
-static inline struct rq *scx_locked_rq(void)
-{
-	return __this_cpu_read(scx_locked_rq_state);
-}
-
 void scx_tick(struct rq *rq);
 void init_scx_entity(struct sched_ext_entity *scx);
 void scx_pre_fork(struct task_struct *p);
diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
new file mode 100644
index 000000000000..76690ede8700
--- /dev/null
+++ b/kernel/sched/ext_internal.h
@@ -0,0 +1,1061 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * BPF extensible scheduler class: Documentation/scheduler/sched-ext.rst
+ *
+ * Copyright (c) 2025 Meta Platforms, Inc. and affiliates.
+ * Copyright (c) 2025 Tejun Heo <tj@kernel.org>
+ */
+#define SCX_OP_IDX(op)		(offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void)))
+
+enum scx_consts {
+	SCX_DSP_DFL_MAX_BATCH		= 32,
+	SCX_DSP_MAX_LOOPS		= 32,
+	SCX_WATCHDOG_MAX_TIMEOUT	= 30 * HZ,
+
+	SCX_EXIT_BT_LEN			= 64,
+	SCX_EXIT_MSG_LEN		= 1024,
+	SCX_EXIT_DUMP_DFL_LEN		= 32768,
+
+	SCX_CPUPERF_ONE			= SCHED_CAPACITY_SCALE,
+
+	/*
+	 * Iterating all tasks may take a while. Periodically drop
+	 * scx_tasks_lock to avoid causing e.g. CSD and RCU stalls.
+	 */
+	SCX_TASK_ITER_BATCH		= 32,
+};
+
+enum scx_exit_kind {
+	SCX_EXIT_NONE,
+	SCX_EXIT_DONE,
+
+	SCX_EXIT_UNREG = 64,	/* user-space initiated unregistration */
+	SCX_EXIT_UNREG_BPF,	/* BPF-initiated unregistration */
+	SCX_EXIT_UNREG_KERN,	/* kernel-initiated unregistration */
+	SCX_EXIT_SYSRQ,		/* requested by 'S' sysrq */
+
+	SCX_EXIT_ERROR = 1024,	/* runtime error, error msg contains details */
+	SCX_EXIT_ERROR_BPF,	/* ERROR but triggered through scx_bpf_error() */
+	SCX_EXIT_ERROR_STALL,	/* watchdog detected stalled runnable tasks */
+};
+
+/*
+ * An exit code can be specified when exiting with scx_bpf_exit() or scx_exit(),
+ * corresponding to exit_kind UNREG_BPF and UNREG_KERN respectively. The codes
+ * are 64bit of the format:
+ *
+ *   Bits: [63  ..  48 47   ..  32 31 .. 0]
+ *         [ SYS ACT ] [ SYS RSN ] [ USR  ]
+ *
+ *   SYS ACT: System-defined exit actions
+ *   SYS RSN: System-defined exit reasons
+ *   USR    : User-defined exit codes and reasons
+ *
+ * Using the above, users may communicate intention and context by ORing system
+ * actions and/or system reasons with a user-defined exit code.
+ */
+enum scx_exit_code {
+	/* Reasons */
+	SCX_ECODE_RSN_HOTPLUG	= 1LLU << 32,
+
+	/* Actions */
+	SCX_ECODE_ACT_RESTART	= 1LLU << 48,
+};
+
+/*
+ * scx_exit_info is passed to ops.exit() to describe why the BPF scheduler is
+ * being disabled.
+ */
+struct scx_exit_info {
+	/* %SCX_EXIT_* - broad category of the exit reason */
+	enum scx_exit_kind	kind;
+
+	/* exit code if gracefully exiting */
+	s64			exit_code;
+
+	/* textual representation of the above */
+	const char		*reason;
+
+	/* backtrace if exiting due to an error */
+	unsigned long		*bt;
+	u32			bt_len;
+
+	/* informational message */
+	char			*msg;
+
+	/* debug dump */
+	char			*dump;
+};
+
+/* sched_ext_ops.flags */
+enum scx_ops_flags {
+	/*
+	 * Keep built-in idle tracking even if ops.update_idle() is implemented.
+	 */
+	SCX_OPS_KEEP_BUILTIN_IDLE	= 1LLU << 0,
+
+	/*
+	 * By default, if there are no other task to run on the CPU, ext core
+	 * keeps running the current task even after its slice expires. If this
+	 * flag is specified, such tasks are passed to ops.enqueue() with
+	 * %SCX_ENQ_LAST. See the comment above %SCX_ENQ_LAST for more info.
+	 */
+	SCX_OPS_ENQ_LAST		= 1LLU << 1,
+
+	/*
+	 * An exiting task may schedule after PF_EXITING is set. In such cases,
+	 * bpf_task_from_pid() may not be able to find the task and if the BPF
+	 * scheduler depends on pid lookup for dispatching, the task will be
+	 * lost leading to various issues including RCU grace period stalls.
+	 *
+	 * To mask this problem, by default, unhashed tasks are automatically
+	 * dispatched to the local DSQ on enqueue. If the BPF scheduler doesn't
+	 * depend on pid lookups and wants to handle these tasks directly, the
+	 * following flag can be used.
+	 */
+	SCX_OPS_ENQ_EXITING		= 1LLU << 2,
+
+	/*
+	 * If set, only tasks with policy set to SCHED_EXT are attached to
+	 * sched_ext. If clear, SCHED_NORMAL tasks are also included.
+	 */
+	SCX_OPS_SWITCH_PARTIAL		= 1LLU << 3,
+
+	/*
+	 * A migration disabled task can only execute on its current CPU. By
+	 * default, such tasks are automatically put on the CPU's local DSQ with
+	 * the default slice on enqueue. If this ops flag is set, they also go
+	 * through ops.enqueue().
+	 *
+	 * A migration disabled task never invokes ops.select_cpu() as it can
+	 * only select the current CPU. Also, p->cpus_ptr will only contain its
+	 * current CPU while p->nr_cpus_allowed keeps tracking p->user_cpus_ptr
+	 * and thus may disagree with cpumask_weight(p->cpus_ptr).
+	 */
+	SCX_OPS_ENQ_MIGRATION_DISABLED	= 1LLU << 4,
+
+	/*
+	 * Queued wakeup (ttwu_queue) is a wakeup optimization that invokes
+	 * ops.enqueue() on the ops.select_cpu() selected or the wakee's
+	 * previous CPU via IPI (inter-processor interrupt) to reduce cacheline
+	 * transfers. When this optimization is enabled, ops.select_cpu() is
+	 * skipped in some cases (when racing against the wakee switching out).
+	 * As the BPF scheduler may depend on ops.select_cpu() being invoked
+	 * during wakeups, queued wakeup is disabled by default.
+	 *
+	 * If this ops flag is set, queued wakeup optimization is enabled and
+	 * the BPF scheduler must be able to handle ops.enqueue() invoked on the
+	 * wakee's CPU without preceding ops.select_cpu() even for tasks which
+	 * may be executed on multiple CPUs.
+	 */
+	SCX_OPS_ALLOW_QUEUED_WAKEUP	= 1LLU << 5,
+
+	/*
+	 * If set, enable per-node idle cpumasks. If clear, use a single global
+	 * flat idle cpumask.
+	 */
+	SCX_OPS_BUILTIN_IDLE_PER_NODE	= 1LLU << 6,
+
+	/*
+	 * CPU cgroup support flags
+	 */
+	SCX_OPS_HAS_CGROUP_WEIGHT	= 1LLU << 16,	/* DEPRECATED, will be removed on 6.18 */
+
+	SCX_OPS_ALL_FLAGS		= SCX_OPS_KEEP_BUILTIN_IDLE |
+					  SCX_OPS_ENQ_LAST |
+					  SCX_OPS_ENQ_EXITING |
+					  SCX_OPS_ENQ_MIGRATION_DISABLED |
+					  SCX_OPS_ALLOW_QUEUED_WAKEUP |
+					  SCX_OPS_SWITCH_PARTIAL |
+					  SCX_OPS_BUILTIN_IDLE_PER_NODE |
+					  SCX_OPS_HAS_CGROUP_WEIGHT,
+
+	/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
+	__SCX_OPS_INTERNAL_MASK		= 0xffLLU << 56,
+
+	SCX_OPS_HAS_CPU_PREEMPT		= 1LLU << 56,
+};
+
+/* argument container for ops.init_task() */
+struct scx_init_task_args {
+	/*
+	 * Set if ops.init_task() is being invoked on the fork path, as opposed
+	 * to the scheduler transition path.
+	 */
+	bool			fork;
+#ifdef CONFIG_EXT_GROUP_SCHED
+	/* the cgroup the task is joining */
+	struct cgroup		*cgroup;
+#endif
+};
+
+/* argument container for ops.exit_task() */
+struct scx_exit_task_args {
+	/* Whether the task exited before running on sched_ext. */
+	bool cancelled;
+};
+
+/* argument container for ops->cgroup_init() */
+struct scx_cgroup_init_args {
+	/* the weight of the cgroup [1..10000] */
+	u32			weight;
+
+	/* bandwidth control parameters from cpu.max and cpu.max.burst */
+	u64			bw_period_us;
+	u64			bw_quota_us;
+	u64			bw_burst_us;
+};
+
+enum scx_cpu_preempt_reason {
+	/* next task is being scheduled by &sched_class_rt */
+	SCX_CPU_PREEMPT_RT,
+	/* next task is being scheduled by &sched_class_dl */
+	SCX_CPU_PREEMPT_DL,
+	/* next task is being scheduled by &sched_class_stop */
+	SCX_CPU_PREEMPT_STOP,
+	/* unknown reason for SCX being preempted */
+	SCX_CPU_PREEMPT_UNKNOWN,
+};
+
+/*
+ * Argument container for ops->cpu_acquire(). Currently empty, but may be
+ * expanded in the future.
+ */
+struct scx_cpu_acquire_args {};
+
+/* argument container for ops->cpu_release() */
+struct scx_cpu_release_args {
+	/* the reason the CPU was preempted */
+	enum scx_cpu_preempt_reason reason;
+
+	/* the task that's going to be scheduled on the CPU */
+	struct task_struct	*task;
+};
+
+/*
+ * Informational context provided to dump operations.
+ */
+struct scx_dump_ctx {
+	enum scx_exit_kind	kind;
+	s64			exit_code;
+	const char		*reason;
+	u64			at_ns;
+	u64			at_jiffies;
+};
+
+/**
+ * struct sched_ext_ops - Operation table for BPF scheduler implementation
+ *
+ * A BPF scheduler can implement an arbitrary scheduling policy by
+ * implementing and loading operations in this table. Note that a userland
+ * scheduling policy can also be implemented using the BPF scheduler
+ * as a shim layer.
+ */
+struct sched_ext_ops {
+	/**
+	 * @select_cpu: Pick the target CPU for a task which is being woken up
+	 * @p: task being woken up
+	 * @prev_cpu: the cpu @p was on before sleeping
+	 * @wake_flags: SCX_WAKE_*
+	 *
+	 * Decision made here isn't final. @p may be moved to any CPU while it
+	 * is getting dispatched for execution later. However, as @p is not on
+	 * the rq at this point, getting the eventual execution CPU right here
+	 * saves a small bit of overhead down the line.
+	 *
+	 * If an idle CPU is returned, the CPU is kicked and will try to
+	 * dispatch. While an explicit custom mechanism can be added,
+	 * select_cpu() serves as the default way to wake up idle CPUs.
+	 *
+	 * @p may be inserted into a DSQ directly by calling
+	 * scx_bpf_dsq_insert(). If so, the ops.enqueue() will be skipped.
+	 * Directly inserting into %SCX_DSQ_LOCAL will put @p in the local DSQ
+	 * of the CPU returned by this operation.
+	 *
+	 * Note that select_cpu() is never called for tasks that can only run
+	 * on a single CPU or tasks with migration disabled, as they don't have
+	 * the option to select a different CPU. See select_task_rq() for
+	 * details.
+	 */
+	s32 (*select_cpu)(struct task_struct *p, s32 prev_cpu, u64 wake_flags);
+
+	/**
+	 * @enqueue: Enqueue a task on the BPF scheduler
+	 * @p: task being enqueued
+	 * @enq_flags: %SCX_ENQ_*
+	 *
+	 * @p is ready to run. Insert directly into a DSQ by calling
+	 * scx_bpf_dsq_insert() or enqueue on the BPF scheduler. If not directly
+	 * inserted, the bpf scheduler owns @p and if it fails to dispatch @p,
+	 * the task will stall.
+	 *
+	 * If @p was inserted into a DSQ from ops.select_cpu(), this callback is
+	 * skipped.
+	 */
+	void (*enqueue)(struct task_struct *p, u64 enq_flags);
+
+	/**
+	 * @dequeue: Remove a task from the BPF scheduler
+	 * @p: task being dequeued
+	 * @deq_flags: %SCX_DEQ_*
+	 *
+	 * Remove @p from the BPF scheduler. This is usually called to isolate
+	 * the task while updating its scheduling properties (e.g. priority).
+	 *
+	 * The ext core keeps track of whether the BPF side owns a given task or
+	 * not and can gracefully ignore spurious dispatches from BPF side,
+	 * which makes it safe to not implement this method. However, depending
+	 * on the scheduling logic, this can lead to confusing behaviors - e.g.
+	 * scheduling position not being updated across a priority change.
+	 */
+	void (*dequeue)(struct task_struct *p, u64 deq_flags);
+
+	/**
+	 * @dispatch: Dispatch tasks from the BPF scheduler and/or user DSQs
+	 * @cpu: CPU to dispatch tasks for
+	 * @prev: previous task being switched out
+	 *
+	 * Called when a CPU's local dsq is empty. The operation should dispatch
+	 * one or more tasks from the BPF scheduler into the DSQs using
+	 * scx_bpf_dsq_insert() and/or move from user DSQs into the local DSQ
+	 * using scx_bpf_dsq_move_to_local().
+	 *
+	 * The maximum number of times scx_bpf_dsq_insert() can be called
+	 * without an intervening scx_bpf_dsq_move_to_local() is specified by
+	 * ops.dispatch_max_batch. See the comments on top of the two functions
+	 * for more details.
+	 *
+	 * When not %NULL, @prev is an SCX task with its slice depleted. If
+	 * @prev is still runnable as indicated by set %SCX_TASK_QUEUED in
+	 * @prev->scx.flags, it is not enqueued yet and will be enqueued after
+	 * ops.dispatch() returns. To keep executing @prev, return without
+	 * dispatching or moving any tasks. Also see %SCX_OPS_ENQ_LAST.
+	 */
+	void (*dispatch)(s32 cpu, struct task_struct *prev);
+
+	/**
+	 * @tick: Periodic tick
+	 * @p: task running currently
+	 *
+	 * This operation is called every 1/HZ seconds on CPUs which are
+	 * executing an SCX task. Setting @p->scx.slice to 0 will trigger an
+	 * immediate dispatch cycle on the CPU.
+	 */
+	void (*tick)(struct task_struct *p);
+
+	/**
+	 * @runnable: A task is becoming runnable on its associated CPU
+	 * @p: task becoming runnable
+	 * @enq_flags: %SCX_ENQ_*
+	 *
+	 * This and the following three functions can be used to track a task's
+	 * execution state transitions. A task becomes ->runnable() on a CPU,
+	 * and then goes through one or more ->running() and ->stopping() pairs
+	 * as it runs on the CPU, and eventually becomes ->quiescent() when it's
+	 * done running on the CPU.
+	 *
+	 * @p is becoming runnable on the CPU because it's
+	 *
+	 * - waking up (%SCX_ENQ_WAKEUP)
+	 * - being moved from another CPU
+	 * - being restored after temporarily taken off the queue for an
+	 *   attribute change.
+	 *
+	 * This and ->enqueue() are related but not coupled. This operation
+	 * notifies @p's state transition and may not be followed by ->enqueue()
+	 * e.g. when @p is being dispatched to a remote CPU, or when @p is
+	 * being enqueued on a CPU experiencing a hotplug event. Likewise, a
+	 * task may be ->enqueue()'d without being preceded by this operation
+	 * e.g. after exhausting its slice.
+	 */
+	void (*runnable)(struct task_struct *p, u64 enq_flags);
+
+	/**
+	 * @running: A task is starting to run on its associated CPU
+	 * @p: task starting to run
+	 *
+	 * Note that this callback may be called from a CPU other than the
+	 * one the task is going to run on. This can happen when a task
+	 * property is changed (i.e., affinity), since scx_next_task_scx(),
+	 * which triggers this callback, may run on a CPU different from
+	 * the task's assigned CPU.
+	 *
+	 * Therefore, always use scx_bpf_task_cpu(@p) to determine the
+	 * target CPU the task is going to use.
+	 *
+	 * See ->runnable() for explanation on the task state notifiers.
+	 */
+	void (*running)(struct task_struct *p);
+
+	/**
+	 * @stopping: A task is stopping execution
+	 * @p: task stopping to run
+	 * @runnable: is task @p still runnable?
+	 *
+	 * Note that this callback may be called from a CPU other than the
+	 * one the task was running on. This can happen when a task
+	 * property is changed (i.e., affinity), since dequeue_task_scx(),
+	 * which triggers this callback, may run on a CPU different from
+	 * the task's assigned CPU.
+	 *
+	 * Therefore, always use scx_bpf_task_cpu(@p) to retrieve the CPU
+	 * the task was running on.
+	 *
+	 * See ->runnable() for explanation on the task state notifiers. If
+	 * !@runnable, ->quiescent() will be invoked after this operation
+	 * returns.
+	 */
+	void (*stopping)(struct task_struct *p, bool runnable);
+
+	/**
+	 * @quiescent: A task is becoming not runnable on its associated CPU
+	 * @p: task becoming not runnable
+	 * @deq_flags: %SCX_DEQ_*
+	 *
+	 * See ->runnable() for explanation on the task state notifiers.
+	 *
+	 * @p is becoming quiescent on the CPU because it's
+	 *
+	 * - sleeping (%SCX_DEQ_SLEEP)
+	 * - being moved to another CPU
+	 * - being temporarily taken off the queue for an attribute change
+	 *   (%SCX_DEQ_SAVE)
+	 *
+	 * This and ->dequeue() are related but not coupled. This operation
+	 * notifies @p's state transition and may not be preceded by ->dequeue()
+	 * e.g. when @p is being dispatched to a remote CPU.
+	 */
+	void (*quiescent)(struct task_struct *p, u64 deq_flags);
+
+	/**
+	 * @yield: Yield CPU
+	 * @from: yielding task
+	 * @to: optional yield target task
+	 *
+	 * If @to is NULL, @from is yielding the CPU to other runnable tasks.
+	 * The BPF scheduler should ensure that other available tasks are
+	 * dispatched before the yielding task. Return value is ignored in this
+	 * case.
+	 *
+	 * If @to is not-NULL, @from wants to yield the CPU to @to. If the bpf
+	 * scheduler can implement the request, return %true; otherwise, %false.
+	 */
+	bool (*yield)(struct task_struct *from, struct task_struct *to);
+
+	/**
+	 * @core_sched_before: Task ordering for core-sched
+	 * @a: task A
+	 * @b: task B
+	 *
+	 * Used by core-sched to determine the ordering between two tasks. See
+	 * Documentation/admin-guide/hw-vuln/core-scheduling.rst for details on
+	 * core-sched.
+	 *
+	 * Both @a and @b are runnable and may or may not currently be queued on
+	 * the BPF scheduler. Should return %true if @a should run before @b.
+	 * %false if there's no required ordering or @b should run before @a.
+	 *
+	 * If not specified, the default is ordering them according to when they
+	 * became runnable.
+	 */
+	bool (*core_sched_before)(struct task_struct *a, struct task_struct *b);
+
+	/**
+	 * @set_weight: Set task weight
+	 * @p: task to set weight for
+	 * @weight: new weight [1..10000]
+	 *
+	 * Update @p's weight to @weight.
+	 */
+	void (*set_weight)(struct task_struct *p, u32 weight);
+
+	/**
+	 * @set_cpumask: Set CPU affinity
+	 * @p: task to set CPU affinity for
+	 * @cpumask: cpumask of cpus that @p can run on
+	 *
+	 * Update @p's CPU affinity to @cpumask.
+	 */
+	void (*set_cpumask)(struct task_struct *p,
+			    const struct cpumask *cpumask);
+
+	/**
+	 * @update_idle: Update the idle state of a CPU
+	 * @cpu: CPU to update the idle state for
+	 * @idle: whether entering or exiting the idle state
+	 *
+	 * This operation is called when @rq's CPU goes or leaves the idle
+	 * state. By default, implementing this operation disables the built-in
+	 * idle CPU tracking and the following helpers become unavailable:
+	 *
+	 * - scx_bpf_select_cpu_dfl()
+	 * - scx_bpf_select_cpu_and()
+	 * - scx_bpf_test_and_clear_cpu_idle()
+	 * - scx_bpf_pick_idle_cpu()
+	 *
+	 * The user also must implement ops.select_cpu() as the default
+	 * implementation relies on scx_bpf_select_cpu_dfl().
+	 *
+	 * Specify the %SCX_OPS_KEEP_BUILTIN_IDLE flag to keep the built-in idle
+	 * tracking.
+	 */
+	void (*update_idle)(s32 cpu, bool idle);
+
+	/**
+	 * @cpu_acquire: A CPU is becoming available to the BPF scheduler
+	 * @cpu: The CPU being acquired by the BPF scheduler.
+	 * @args: Acquire arguments, see the struct definition.
+	 *
+	 * A CPU that was previously released from the BPF scheduler is now once
+	 * again under its control.
+	 */
+	void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
+
+	/**
+	 * @cpu_release: A CPU is taken away from the BPF scheduler
+	 * @cpu: The CPU being released by the BPF scheduler.
+	 * @args: Release arguments, see the struct definition.
+	 *
+	 * The specified CPU is no longer under the control of the BPF
+	 * scheduler. This could be because it was preempted by a higher
+	 * priority sched_class, though there may be other reasons as well. The
+	 * caller should consult @args->reason to determine the cause.
+	 */
+	void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
+
+	/**
+	 * @init_task: Initialize a task to run in a BPF scheduler
+	 * @p: task to initialize for BPF scheduling
+	 * @args: init arguments, see the struct definition
+	 *
+	 * Either we're loading a BPF scheduler or a new task is being forked.
+	 * Initialize @p for BPF scheduling. This operation may block and can
+	 * be used for allocations, and is called exactly once for a task.
+	 *
+	 * Return 0 for success, -errno for failure. An error return while
+	 * loading will abort loading of the BPF scheduler. During a fork, it
+	 * will abort that specific fork.
+	 */
+	s32 (*init_task)(struct task_struct *p, struct scx_init_task_args *args);
+
+	/**
+	 * @exit_task: Exit a previously-running task from the system
+	 * @p: task to exit
+	 * @args: exit arguments, see the struct definition
+	 *
+	 * @p is exiting or the BPF scheduler is being unloaded. Perform any
+	 * necessary cleanup for @p.
+	 */
+	void (*exit_task)(struct task_struct *p, struct scx_exit_task_args *args);
+
+	/**
+	 * @enable: Enable BPF scheduling for a task
+	 * @p: task to enable BPF scheduling for
+	 *
+	 * Enable @p for BPF scheduling. enable() is called on @p any time it
+	 * enters SCX, and is always paired with a matching disable().
+	 */
+	void (*enable)(struct task_struct *p);
+
+	/**
+	 * @disable: Disable BPF scheduling for a task
+	 * @p: task to disable BPF scheduling for
+	 *
+	 * @p is exiting, leaving SCX or the BPF scheduler is being unloaded.
+	 * Disable BPF scheduling for @p. A disable() call is always matched
+	 * with a prior enable() call.
+	 */
+	void (*disable)(struct task_struct *p);
+
+	/**
+	 * @dump: Dump BPF scheduler state on error
+	 * @ctx: debug dump context
+	 *
+	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump.
+	 */
+	void (*dump)(struct scx_dump_ctx *ctx);
+
+	/**
+	 * @dump_cpu: Dump BPF scheduler state for a CPU on error
+	 * @ctx: debug dump context
+	 * @cpu: CPU to generate debug dump for
+	 * @idle: @cpu is currently idle without any runnable tasks
+	 *
+	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
+	 * @cpu. If @idle is %true and this operation doesn't produce any
+	 * output, @cpu is skipped for dump.
+	 */
+	void (*dump_cpu)(struct scx_dump_ctx *ctx, s32 cpu, bool idle);
+
+	/**
+	 * @dump_task: Dump BPF scheduler state for a runnable task on error
+	 * @ctx: debug dump context
+	 * @p: runnable task to generate debug dump for
+	 *
+	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
+	 * @p.
+	 */
+	void (*dump_task)(struct scx_dump_ctx *ctx, struct task_struct *p);
+
+#ifdef CONFIG_EXT_GROUP_SCHED
+	/**
+	 * @cgroup_init: Initialize a cgroup
+	 * @cgrp: cgroup being initialized
+	 * @args: init arguments, see the struct definition
+	 *
+	 * Either the BPF scheduler is being loaded or @cgrp created, initialize
+	 * @cgrp for sched_ext. This operation may block.
+	 *
+	 * Return 0 for success, -errno for failure. An error return while
+	 * loading will abort loading of the BPF scheduler. During cgroup
+	 * creation, it will abort the specific cgroup creation.
+	 */
+	s32 (*cgroup_init)(struct cgroup *cgrp,
+			   struct scx_cgroup_init_args *args);
+
+	/**
+	 * @cgroup_exit: Exit a cgroup
+	 * @cgrp: cgroup being exited
+	 *
+	 * Either the BPF scheduler is being unloaded or @cgrp destroyed, exit
+	 * @cgrp for sched_ext. This operation my block.
+	 */
+	void (*cgroup_exit)(struct cgroup *cgrp);
+
+	/**
+	 * @cgroup_prep_move: Prepare a task to be moved to a different cgroup
+	 * @p: task being moved
+	 * @from: cgroup @p is being moved from
+	 * @to: cgroup @p is being moved to
+	 *
+	 * Prepare @p for move from cgroup @from to @to. This operation may
+	 * block and can be used for allocations.
+	 *
+	 * Return 0 for success, -errno for failure. An error return aborts the
+	 * migration.
+	 */
+	s32 (*cgroup_prep_move)(struct task_struct *p,
+				struct cgroup *from, struct cgroup *to);
+
+	/**
+	 * @cgroup_move: Commit cgroup move
+	 * @p: task being moved
+	 * @from: cgroup @p is being moved from
+	 * @to: cgroup @p is being moved to
+	 *
+	 * Commit the move. @p is dequeued during this operation.
+	 */
+	void (*cgroup_move)(struct task_struct *p,
+			    struct cgroup *from, struct cgroup *to);
+
+	/**
+	 * @cgroup_cancel_move: Cancel cgroup move
+	 * @p: task whose cgroup move is being canceled
+	 * @from: cgroup @p was being moved from
+	 * @to: cgroup @p was being moved to
+	 *
+	 * @p was cgroup_prep_move()'d but failed before reaching cgroup_move().
+	 * Undo the preparation.
+	 */
+	void (*cgroup_cancel_move)(struct task_struct *p,
+				   struct cgroup *from, struct cgroup *to);
+
+	/**
+	 * @cgroup_set_weight: A cgroup's weight is being changed
+	 * @cgrp: cgroup whose weight is being updated
+	 * @weight: new weight [1..10000]
+	 *
+	 * Update @cgrp's weight to @weight.
+	 */
+	void (*cgroup_set_weight)(struct cgroup *cgrp, u32 weight);
+
+	/**
+	 * @cgroup_set_bandwidth: A cgroup's bandwidth is being changed
+	 * @cgrp: cgroup whose bandwidth is being updated
+	 * @period_us: bandwidth control period
+	 * @quota_us: bandwidth control quota
+	 * @burst_us: bandwidth control burst
+	 *
+	 * Update @cgrp's bandwidth control parameters. This is from the cpu.max
+	 * cgroup interface.
+	 *
+	 * @quota_us / @period_us determines the CPU bandwidth @cgrp is entitled
+	 * to. For example, if @period_us is 1_000_000 and @quota_us is
+	 * 2_500_000. @cgrp is entitled to 2.5 CPUs. @burst_us can be
+	 * interpreted in the same fashion and specifies how much @cgrp can
+	 * burst temporarily. The specific control mechanism and thus the
+	 * interpretation of @period_us and burstiness is upto to the BPF
+	 * scheduler.
+	 */
+	void (*cgroup_set_bandwidth)(struct cgroup *cgrp,
+				     u64 period_us, u64 quota_us, u64 burst_us);
+
+#endif	/* CONFIG_EXT_GROUP_SCHED */
+
+	/*
+	 * All online ops must come before ops.cpu_online().
+	 */
+
+	/**
+	 * @cpu_online: A CPU became online
+	 * @cpu: CPU which just came up
+	 *
+	 * @cpu just came online. @cpu will not call ops.enqueue() or
+	 * ops.dispatch(), nor run tasks associated with other CPUs beforehand.
+	 */
+	void (*cpu_online)(s32 cpu);
+
+	/**
+	 * @cpu_offline: A CPU is going offline
+	 * @cpu: CPU which is going offline
+	 *
+	 * @cpu is going offline. @cpu will not call ops.enqueue() or
+	 * ops.dispatch(), nor run tasks associated with other CPUs afterwards.
+	 */
+	void (*cpu_offline)(s32 cpu);
+
+	/*
+	 * All CPU hotplug ops must come before ops.init().
+	 */
+
+	/**
+	 * @init: Initialize the BPF scheduler
+	 */
+	s32 (*init)(void);
+
+	/**
+	 * @exit: Clean up after the BPF scheduler
+	 * @info: Exit info
+	 *
+	 * ops.exit() is also called on ops.init() failure, which is a bit
+	 * unusual. This is to allow rich reporting through @info on how
+	 * ops.init() failed.
+	 */
+	void (*exit)(struct scx_exit_info *info);
+
+	/**
+	 * @dispatch_max_batch: Max nr of tasks that dispatch() can dispatch
+	 */
+	u32 dispatch_max_batch;
+
+	/**
+	 * @flags: %SCX_OPS_* flags
+	 */
+	u64 flags;
+
+	/**
+	 * @timeout_ms: The maximum amount of time, in milliseconds, that a
+	 * runnable task should be able to wait before being scheduled. The
+	 * maximum timeout may not exceed the default timeout of 30 seconds.
+	 *
+	 * Defaults to the maximum allowed timeout value of 30 seconds.
+	 */
+	u32 timeout_ms;
+
+	/**
+	 * @exit_dump_len: scx_exit_info.dump buffer length. If 0, the default
+	 * value of 32768 is used.
+	 */
+	u32 exit_dump_len;
+
+	/**
+	 * @hotplug_seq: A sequence number that may be set by the scheduler to
+	 * detect when a hotplug event has occurred during the loading process.
+	 * If 0, no detection occurs. Otherwise, the scheduler will fail to
+	 * load if the sequence number does not match @scx_hotplug_seq on the
+	 * enable path.
+	 */
+	u64 hotplug_seq;
+
+	/**
+	 * @name: BPF scheduler's name
+	 *
+	 * Must be a non-zero valid BPF object name including only isalnum(),
+	 * '_' and '.' chars. Shows up in kernel.sched_ext_ops sysctl while the
+	 * BPF scheduler is enabled.
+	 */
+	char name[SCX_OPS_NAME_LEN];
+
+	/* internal use only, must be NULL */
+	void *priv;
+};
+
+enum scx_opi {
+	SCX_OPI_BEGIN			= 0,
+	SCX_OPI_NORMAL_BEGIN		= 0,
+	SCX_OPI_NORMAL_END		= SCX_OP_IDX(cpu_online),
+	SCX_OPI_CPU_HOTPLUG_BEGIN	= SCX_OP_IDX(cpu_online),
+	SCX_OPI_CPU_HOTPLUG_END		= SCX_OP_IDX(init),
+	SCX_OPI_END			= SCX_OP_IDX(init),
+};
+
+/*
+ * Collection of event counters. Event types are placed in descending order.
+ */
+struct scx_event_stats {
+	/*
+	 * If ops.select_cpu() returns a CPU which can't be used by the task,
+	 * the core scheduler code silently picks a fallback CPU.
+	 */
+	s64		SCX_EV_SELECT_CPU_FALLBACK;
+
+	/*
+	 * When dispatching to a local DSQ, the CPU may have gone offline in
+	 * the meantime. In this case, the task is bounced to the global DSQ.
+	 */
+	s64		SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE;
+
+	/*
+	 * If SCX_OPS_ENQ_LAST is not set, the number of times that a task
+	 * continued to run because there were no other tasks on the CPU.
+	 */
+	s64		SCX_EV_DISPATCH_KEEP_LAST;
+
+	/*
+	 * If SCX_OPS_ENQ_EXITING is not set, the number of times that a task
+	 * is dispatched to a local DSQ when exiting.
+	 */
+	s64		SCX_EV_ENQ_SKIP_EXITING;
+
+	/*
+	 * If SCX_OPS_ENQ_MIGRATION_DISABLED is not set, the number of times a
+	 * migration disabled task skips ops.enqueue() and is dispatched to its
+	 * local DSQ.
+	 */
+	s64		SCX_EV_ENQ_SKIP_MIGRATION_DISABLED;
+
+	/*
+	 * Total number of times a task's time slice was refilled with the
+	 * default value (SCX_SLICE_DFL).
+	 */
+	s64		SCX_EV_REFILL_SLICE_DFL;
+
+	/*
+	 * The total duration of bypass modes in nanoseconds.
+	 */
+	s64		SCX_EV_BYPASS_DURATION;
+
+	/*
+	 * The number of tasks dispatched in the bypassing mode.
+	 */
+	s64		SCX_EV_BYPASS_DISPATCH;
+
+	/*
+	 * The number of times the bypassing mode has been activated.
+	 */
+	s64		SCX_EV_BYPASS_ACTIVATE;
+};
+
+struct scx_sched {
+	struct sched_ext_ops	ops;
+	DECLARE_BITMAP(has_op, SCX_OPI_END);
+
+	/*
+	 * Dispatch queues.
+	 *
+	 * The global DSQ (%SCX_DSQ_GLOBAL) is split per-node for scalability.
+	 * This is to avoid live-locking in bypass mode where all tasks are
+	 * dispatched to %SCX_DSQ_GLOBAL and all CPUs consume from it. If
+	 * per-node split isn't sufficient, it can be further split.
+	 */
+	struct rhashtable	dsq_hash;
+	struct scx_dispatch_q	**global_dsqs;
+
+	/*
+	 * The event counters are in a per-CPU variable to minimize the
+	 * accounting overhead. A system-wide view on the event counter is
+	 * constructed when requested by scx_bpf_events().
+	 */
+	struct scx_event_stats __percpu *event_stats_cpu;
+
+	bool			warned_zero_slice;
+
+	atomic_t		exit_kind;
+	struct scx_exit_info	*exit_info;
+
+	struct kobject		kobj;
+
+	struct kthread_worker	*helper;
+	struct irq_work		error_irq_work;
+	struct kthread_work	disable_work;
+	struct rcu_work		rcu_work;
+};
+
+enum scx_wake_flags {
+	/* expose select WF_* flags as enums */
+	SCX_WAKE_FORK		= WF_FORK,
+	SCX_WAKE_TTWU		= WF_TTWU,
+	SCX_WAKE_SYNC		= WF_SYNC,
+};
+
+enum scx_enq_flags {
+	/* expose select ENQUEUE_* flags as enums */
+	SCX_ENQ_WAKEUP		= ENQUEUE_WAKEUP,
+	SCX_ENQ_HEAD		= ENQUEUE_HEAD,
+	SCX_ENQ_CPU_SELECTED	= ENQUEUE_RQ_SELECTED,
+
+	/* high 32bits are SCX specific */
+
+	/*
+	 * Set the following to trigger preemption when calling
+	 * scx_bpf_dsq_insert() with a local dsq as the target. The slice of the
+	 * current task is cleared to zero and the CPU is kicked into the
+	 * scheduling path. Implies %SCX_ENQ_HEAD.
+	 */
+	SCX_ENQ_PREEMPT		= 1LLU << 32,
+
+	/*
+	 * The task being enqueued was previously enqueued on the current CPU's
+	 * %SCX_DSQ_LOCAL, but was removed from it in a call to the
+	 * scx_bpf_reenqueue_local() kfunc. If scx_bpf_reenqueue_local() was
+	 * invoked in a ->cpu_release() callback, and the task is again
+	 * dispatched back to %SCX_LOCAL_DSQ by this current ->enqueue(), the
+	 * task will not be scheduled on the CPU until at least the next invocation
+	 * of the ->cpu_acquire() callback.
+	 */
+	SCX_ENQ_REENQ		= 1LLU << 40,
+
+	/*
+	 * The task being enqueued is the only task available for the cpu. By
+	 * default, ext core keeps executing such tasks but when
+	 * %SCX_OPS_ENQ_LAST is specified, they're ops.enqueue()'d with the
+	 * %SCX_ENQ_LAST flag set.
+	 *
+	 * The BPF scheduler is responsible for triggering a follow-up
+	 * scheduling event. Otherwise, Execution may stall.
+	 */
+	SCX_ENQ_LAST		= 1LLU << 41,
+
+	/* high 8 bits are internal */
+	__SCX_ENQ_INTERNAL_MASK	= 0xffLLU << 56,
+
+	SCX_ENQ_CLEAR_OPSS	= 1LLU << 56,
+	SCX_ENQ_DSQ_PRIQ	= 1LLU << 57,
+};
+
+enum scx_deq_flags {
+	/* expose select DEQUEUE_* flags as enums */
+	SCX_DEQ_SLEEP		= DEQUEUE_SLEEP,
+
+	/* high 32bits are SCX specific */
+
+	/*
+	 * The generic core-sched layer decided to execute the task even though
+	 * it hasn't been dispatched yet. Dequeue from the BPF side.
+	 */
+	SCX_DEQ_CORE_SCHED_EXEC	= 1LLU << 32,
+};
+
+enum scx_pick_idle_cpu_flags {
+	SCX_PICK_IDLE_CORE	= 1LLU << 0,	/* pick a CPU whose SMT siblings are also idle */
+	SCX_PICK_IDLE_IN_NODE	= 1LLU << 1,	/* pick a CPU in the same target NUMA node */
+};
+
+enum scx_kick_flags {
+	/*
+	 * Kick the target CPU if idle. Guarantees that the target CPU goes
+	 * through at least one full scheduling cycle before going idle. If the
+	 * target CPU can be determined to be currently not idle and going to go
+	 * through a scheduling cycle before going idle, noop.
+	 */
+	SCX_KICK_IDLE		= 1LLU << 0,
+
+	/*
+	 * Preempt the current task and execute the dispatch path. If the
+	 * current task of the target CPU is an SCX task, its ->scx.slice is
+	 * cleared to zero before the scheduling path is invoked so that the
+	 * task expires and the dispatch path is invoked.
+	 */
+	SCX_KICK_PREEMPT	= 1LLU << 1,
+
+	/*
+	 * Wait for the CPU to be rescheduled. The scx_bpf_kick_cpu() call will
+	 * return after the target CPU finishes picking the next task.
+	 */
+	SCX_KICK_WAIT		= 1LLU << 2,
+};
+
+enum scx_tg_flags {
+	SCX_TG_ONLINE		= 1U << 0,
+	SCX_TG_INITED		= 1U << 1,
+};
+
+enum scx_enable_state {
+	SCX_ENABLING,
+	SCX_ENABLED,
+	SCX_DISABLING,
+	SCX_DISABLED,
+};
+
+static const char *scx_enable_state_str[] = {
+	[SCX_ENABLING]		= "enabling",
+	[SCX_ENABLED]		= "enabled",
+	[SCX_DISABLING]		= "disabling",
+	[SCX_DISABLED]		= "disabled",
+};
+
+/*
+ * sched_ext_entity->ops_state
+ *
+ * Used to track the task ownership between the SCX core and the BPF scheduler.
+ * State transitions look as follows:
+ *
+ * NONE -> QUEUEING -> QUEUED -> DISPATCHING
+ *   ^              |                 |
+ *   |              v                 v
+ *   \-------------------------------/
+ *
+ * QUEUEING and DISPATCHING states can be waited upon. See wait_ops_state() call
+ * sites for explanations on the conditions being waited upon and why they are
+ * safe. Transitions out of them into NONE or QUEUED must store_release and the
+ * waiters should load_acquire.
+ *
+ * Tracking scx_ops_state enables sched_ext core to reliably determine whether
+ * any given task can be dispatched by the BPF scheduler at all times and thus
+ * relaxes the requirements on the BPF scheduler. This allows the BPF scheduler
+ * to try to dispatch any task anytime regardless of its state as the SCX core
+ * can safely reject invalid dispatches.
+ */
+enum scx_ops_state {
+	SCX_OPSS_NONE,		/* owned by the SCX core */
+	SCX_OPSS_QUEUEING,	/* in transit to the BPF scheduler */
+	SCX_OPSS_QUEUED,	/* owned by the BPF scheduler */
+	SCX_OPSS_DISPATCHING,	/* in transit back to the SCX core */
+
+	/*
+	 * QSEQ brands each QUEUED instance so that, when dispatch races
+	 * dequeue/requeue, the dispatcher can tell whether it still has a claim
+	 * on the task being dispatched.
+	 *
+	 * As some 32bit archs can't do 64bit store_release/load_acquire,
+	 * p->scx.ops_state is atomic_long_t which leaves 30 bits for QSEQ on
+	 * 32bit machines. The dispatch race window QSEQ protects is very narrow
+	 * and runs with IRQ disabled. 30 bits should be sufficient.
+	 */
+	SCX_OPSS_QSEQ_SHIFT	= 2,
+};
+
+/* Use macros to ensure that the type is unsigned long for the masks */
+#define SCX_OPSS_STATE_MASK	((1LU << SCX_OPSS_QSEQ_SHIFT) - 1)
+#define SCX_OPSS_QSEQ_MASK	(~SCX_OPSS_STATE_MASK)
+
+DECLARE_PER_CPU(struct rq *, scx_locked_rq_state);
+
+/*
+ * Return the rq currently locked from an scx callback, or NULL if no rq is
+ * locked.
+ */
+static inline struct rq *scx_locked_rq(void)
+{
+	return __this_cpu_read(scx_locked_rq_state);
+}
+
+static inline bool scx_kf_allowed_if_unlocked(void)
+{
+	return !current->scx.kf_mask;
+}
+
+static inline bool scx_rq_bypassing(struct rq *rq)
+{
+	return unlikely(rq->scx.flags & SCX_RQ_BYPASSING);
+}
-- 
2.51.0

Re: [PATCH 3/4] sched_ext: Move internal type and accessor definitions to ext_internal.h

[Andrea Righi]

On Tue, Sep 02, 2025 at 01:48:05PM -1000, Tejun Heo wrote:
> There currently isn't a place to place SCX-internal types and accessors to
> be shared between ext.c and ext_idle.c. Create kernel/sched/ext_internal.h
> and move internal type and accessor definitions there. This trims ext.c a
> bit and makes future additions easier. Pure code reorganization. No
> functional changes.

Having sched_ext_ops and scx_*_flags defined in ext_internal.h feels a
bit counterintuitive, sched_ext_ops also includes the documentation for all
the scx callbacks. How about moving these to ext.h and everything else in
ext_internal.h?

Thanks,
-Andrea

> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> ---
>  kernel/sched/build_policy.c |    1 +
>  kernel/sched/ext.c          | 1034 ----------------------------------
>  kernel/sched/ext.h          |   23 -
>  kernel/sched/ext_internal.h | 1061 +++++++++++++++++++++++++++++++++++
>  4 files changed, 1062 insertions(+), 1057 deletions(-)
>  create mode 100644 kernel/sched/ext_internal.h
> 
> diff --git a/kernel/sched/build_policy.c b/kernel/sched/build_policy.c
> index c4a488e67aa7..755883faf751 100644
> --- a/kernel/sched/build_policy.c
> +++ b/kernel/sched/build_policy.c
> @@ -58,6 +58,7 @@
>  #include "deadline.c"
>  
>  #ifdef CONFIG_SCHED_CLASS_EXT
> +# include "ext_internal.h"
>  # include "ext.c"
>  # include "ext_idle.c"
>  #endif
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index fda2b4e85ee3..7e15e852370c 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -9,1040 +9,6 @@
>  #include <linux/btf_ids.h>
>  #include "ext_idle.h"
>  
> -#define SCX_OP_IDX(op)		(offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void)))
> -
> -enum scx_consts {
> -	SCX_DSP_DFL_MAX_BATCH		= 32,
> -	SCX_DSP_MAX_LOOPS		= 32,
> -	SCX_WATCHDOG_MAX_TIMEOUT	= 30 * HZ,
> -
> -	SCX_EXIT_BT_LEN			= 64,
> -	SCX_EXIT_MSG_LEN		= 1024,
> -	SCX_EXIT_DUMP_DFL_LEN		= 32768,
> -
> -	SCX_CPUPERF_ONE			= SCHED_CAPACITY_SCALE,
> -
> -	/*
> -	 * Iterating all tasks may take a while. Periodically drop
> -	 * scx_tasks_lock to avoid causing e.g. CSD and RCU stalls.
> -	 */
> -	SCX_TASK_ITER_BATCH		= 32,
> -};
> -
> -enum scx_exit_kind {
> -	SCX_EXIT_NONE,
> -	SCX_EXIT_DONE,
> -
> -	SCX_EXIT_UNREG = 64,	/* user-space initiated unregistration */
> -	SCX_EXIT_UNREG_BPF,	/* BPF-initiated unregistration */
> -	SCX_EXIT_UNREG_KERN,	/* kernel-initiated unregistration */
> -	SCX_EXIT_SYSRQ,		/* requested by 'S' sysrq */
> -
> -	SCX_EXIT_ERROR = 1024,	/* runtime error, error msg contains details */
> -	SCX_EXIT_ERROR_BPF,	/* ERROR but triggered through scx_bpf_error() */
> -	SCX_EXIT_ERROR_STALL,	/* watchdog detected stalled runnable tasks */
> -};
> -
> -/*
> - * An exit code can be specified when exiting with scx_bpf_exit() or scx_exit(),
> - * corresponding to exit_kind UNREG_BPF and UNREG_KERN respectively. The codes
> - * are 64bit of the format:
> - *
> - *   Bits: [63  ..  48 47   ..  32 31 .. 0]
> - *         [ SYS ACT ] [ SYS RSN ] [ USR  ]
> - *
> - *   SYS ACT: System-defined exit actions
> - *   SYS RSN: System-defined exit reasons
> - *   USR    : User-defined exit codes and reasons
> - *
> - * Using the above, users may communicate intention and context by ORing system
> - * actions and/or system reasons with a user-defined exit code.
> - */
> -enum scx_exit_code {
> -	/* Reasons */
> -	SCX_ECODE_RSN_HOTPLUG	= 1LLU << 32,
> -
> -	/* Actions */
> -	SCX_ECODE_ACT_RESTART	= 1LLU << 48,
> -};
> -
> -/*
> - * scx_exit_info is passed to ops.exit() to describe why the BPF scheduler is
> - * being disabled.
> - */
> -struct scx_exit_info {
> -	/* %SCX_EXIT_* - broad category of the exit reason */
> -	enum scx_exit_kind	kind;
> -
> -	/* exit code if gracefully exiting */
> -	s64			exit_code;
> -
> -	/* textual representation of the above */
> -	const char		*reason;
> -
> -	/* backtrace if exiting due to an error */
> -	unsigned long		*bt;
> -	u32			bt_len;
> -
> -	/* informational message */
> -	char			*msg;
> -
> -	/* debug dump */
> -	char			*dump;
> -};
> -
> -/* sched_ext_ops.flags */
> -enum scx_ops_flags {
> -	/*
> -	 * Keep built-in idle tracking even if ops.update_idle() is implemented.
> -	 */
> -	SCX_OPS_KEEP_BUILTIN_IDLE	= 1LLU << 0,
> -
> -	/*
> -	 * By default, if there are no other task to run on the CPU, ext core
> -	 * keeps running the current task even after its slice expires. If this
> -	 * flag is specified, such tasks are passed to ops.enqueue() with
> -	 * %SCX_ENQ_LAST. See the comment above %SCX_ENQ_LAST for more info.
> -	 */
> -	SCX_OPS_ENQ_LAST		= 1LLU << 1,
> -
> -	/*
> -	 * An exiting task may schedule after PF_EXITING is set. In such cases,
> -	 * bpf_task_from_pid() may not be able to find the task and if the BPF
> -	 * scheduler depends on pid lookup for dispatching, the task will be
> -	 * lost leading to various issues including RCU grace period stalls.
> -	 *
> -	 * To mask this problem, by default, unhashed tasks are automatically
> -	 * dispatched to the local DSQ on enqueue. If the BPF scheduler doesn't
> -	 * depend on pid lookups and wants to handle these tasks directly, the
> -	 * following flag can be used.
> -	 */
> -	SCX_OPS_ENQ_EXITING		= 1LLU << 2,
> -
> -	/*
> -	 * If set, only tasks with policy set to SCHED_EXT are attached to
> -	 * sched_ext. If clear, SCHED_NORMAL tasks are also included.
> -	 */
> -	SCX_OPS_SWITCH_PARTIAL		= 1LLU << 3,
> -
> -	/*
> -	 * A migration disabled task can only execute on its current CPU. By
> -	 * default, such tasks are automatically put on the CPU's local DSQ with
> -	 * the default slice on enqueue. If this ops flag is set, they also go
> -	 * through ops.enqueue().
> -	 *
> -	 * A migration disabled task never invokes ops.select_cpu() as it can
> -	 * only select the current CPU. Also, p->cpus_ptr will only contain its
> -	 * current CPU while p->nr_cpus_allowed keeps tracking p->user_cpus_ptr
> -	 * and thus may disagree with cpumask_weight(p->cpus_ptr).
> -	 */
> -	SCX_OPS_ENQ_MIGRATION_DISABLED	= 1LLU << 4,
> -
> -	/*
> -	 * Queued wakeup (ttwu_queue) is a wakeup optimization that invokes
> -	 * ops.enqueue() on the ops.select_cpu() selected or the wakee's
> -	 * previous CPU via IPI (inter-processor interrupt) to reduce cacheline
> -	 * transfers. When this optimization is enabled, ops.select_cpu() is
> -	 * skipped in some cases (when racing against the wakee switching out).
> -	 * As the BPF scheduler may depend on ops.select_cpu() being invoked
> -	 * during wakeups, queued wakeup is disabled by default.
> -	 *
> -	 * If this ops flag is set, queued wakeup optimization is enabled and
> -	 * the BPF scheduler must be able to handle ops.enqueue() invoked on the
> -	 * wakee's CPU without preceding ops.select_cpu() even for tasks which
> -	 * may be executed on multiple CPUs.
> -	 */
> -	SCX_OPS_ALLOW_QUEUED_WAKEUP	= 1LLU << 5,
> -
> -	/*
> -	 * If set, enable per-node idle cpumasks. If clear, use a single global
> -	 * flat idle cpumask.
> -	 */
> -	SCX_OPS_BUILTIN_IDLE_PER_NODE	= 1LLU << 6,
> -
> -	/*
> -	 * CPU cgroup support flags
> -	 */
> -	SCX_OPS_HAS_CGROUP_WEIGHT	= 1LLU << 16,	/* DEPRECATED, will be removed on 6.18 */
> -
> -	SCX_OPS_ALL_FLAGS		= SCX_OPS_KEEP_BUILTIN_IDLE |
> -					  SCX_OPS_ENQ_LAST |
> -					  SCX_OPS_ENQ_EXITING |
> -					  SCX_OPS_ENQ_MIGRATION_DISABLED |
> -					  SCX_OPS_ALLOW_QUEUED_WAKEUP |
> -					  SCX_OPS_SWITCH_PARTIAL |
> -					  SCX_OPS_BUILTIN_IDLE_PER_NODE |
> -					  SCX_OPS_HAS_CGROUP_WEIGHT,
> -
> -	/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
> -	__SCX_OPS_INTERNAL_MASK		= 0xffLLU << 56,
> -
> -	SCX_OPS_HAS_CPU_PREEMPT		= 1LLU << 56,
> -};
> -
> -/* argument container for ops.init_task() */
> -struct scx_init_task_args {
> -	/*
> -	 * Set if ops.init_task() is being invoked on the fork path, as opposed
> -	 * to the scheduler transition path.
> -	 */
> -	bool			fork;
> -#ifdef CONFIG_EXT_GROUP_SCHED
> -	/* the cgroup the task is joining */
> -	struct cgroup		*cgroup;
> -#endif
> -};
> -
> -/* argument container for ops.exit_task() */
> -struct scx_exit_task_args {
> -	/* Whether the task exited before running on sched_ext. */
> -	bool cancelled;
> -};
> -
> -/* argument container for ops->cgroup_init() */
> -struct scx_cgroup_init_args {
> -	/* the weight of the cgroup [1..10000] */
> -	u32			weight;
> -
> -	/* bandwidth control parameters from cpu.max and cpu.max.burst */
> -	u64			bw_period_us;
> -	u64			bw_quota_us;
> -	u64			bw_burst_us;
> -};
> -
> -enum scx_cpu_preempt_reason {
> -	/* next task is being scheduled by &sched_class_rt */
> -	SCX_CPU_PREEMPT_RT,
> -	/* next task is being scheduled by &sched_class_dl */
> -	SCX_CPU_PREEMPT_DL,
> -	/* next task is being scheduled by &sched_class_stop */
> -	SCX_CPU_PREEMPT_STOP,
> -	/* unknown reason for SCX being preempted */
> -	SCX_CPU_PREEMPT_UNKNOWN,
> -};
> -
> -/*
> - * Argument container for ops->cpu_acquire(). Currently empty, but may be
> - * expanded in the future.
> - */
> -struct scx_cpu_acquire_args {};
> -
> -/* argument container for ops->cpu_release() */
> -struct scx_cpu_release_args {
> -	/* the reason the CPU was preempted */
> -	enum scx_cpu_preempt_reason reason;
> -
> -	/* the task that's going to be scheduled on the CPU */
> -	struct task_struct	*task;
> -};
> -
> -/*
> - * Informational context provided to dump operations.
> - */
> -struct scx_dump_ctx {
> -	enum scx_exit_kind	kind;
> -	s64			exit_code;
> -	const char		*reason;
> -	u64			at_ns;
> -	u64			at_jiffies;
> -};
> -
> -/**
> - * struct sched_ext_ops - Operation table for BPF scheduler implementation
> - *
> - * A BPF scheduler can implement an arbitrary scheduling policy by
> - * implementing and loading operations in this table. Note that a userland
> - * scheduling policy can also be implemented using the BPF scheduler
> - * as a shim layer.
> - */
> -struct sched_ext_ops {
> -	/**
> -	 * @select_cpu: Pick the target CPU for a task which is being woken up
> -	 * @p: task being woken up
> -	 * @prev_cpu: the cpu @p was on before sleeping
> -	 * @wake_flags: SCX_WAKE_*
> -	 *
> -	 * Decision made here isn't final. @p may be moved to any CPU while it
> -	 * is getting dispatched for execution later. However, as @p is not on
> -	 * the rq at this point, getting the eventual execution CPU right here
> -	 * saves a small bit of overhead down the line.
> -	 *
> -	 * If an idle CPU is returned, the CPU is kicked and will try to
> -	 * dispatch. While an explicit custom mechanism can be added,
> -	 * select_cpu() serves as the default way to wake up idle CPUs.
> -	 *
> -	 * @p may be inserted into a DSQ directly by calling
> -	 * scx_bpf_dsq_insert(). If so, the ops.enqueue() will be skipped.
> -	 * Directly inserting into %SCX_DSQ_LOCAL will put @p in the local DSQ
> -	 * of the CPU returned by this operation.
> -	 *
> -	 * Note that select_cpu() is never called for tasks that can only run
> -	 * on a single CPU or tasks with migration disabled, as they don't have
> -	 * the option to select a different CPU. See select_task_rq() for
> -	 * details.
> -	 */
> -	s32 (*select_cpu)(struct task_struct *p, s32 prev_cpu, u64 wake_flags);
> -
> -	/**
> -	 * @enqueue: Enqueue a task on the BPF scheduler
> -	 * @p: task being enqueued
> -	 * @enq_flags: %SCX_ENQ_*
> -	 *
> -	 * @p is ready to run. Insert directly into a DSQ by calling
> -	 * scx_bpf_dsq_insert() or enqueue on the BPF scheduler. If not directly
> -	 * inserted, the bpf scheduler owns @p and if it fails to dispatch @p,
> -	 * the task will stall.
> -	 *
> -	 * If @p was inserted into a DSQ from ops.select_cpu(), this callback is
> -	 * skipped.
> -	 */
> -	void (*enqueue)(struct task_struct *p, u64 enq_flags);
> -
> -	/**
> -	 * @dequeue: Remove a task from the BPF scheduler
> -	 * @p: task being dequeued
> -	 * @deq_flags: %SCX_DEQ_*
> -	 *
> -	 * Remove @p from the BPF scheduler. This is usually called to isolate
> -	 * the task while updating its scheduling properties (e.g. priority).
> -	 *
> -	 * The ext core keeps track of whether the BPF side owns a given task or
> -	 * not and can gracefully ignore spurious dispatches from BPF side,
> -	 * which makes it safe to not implement this method. However, depending
> -	 * on the scheduling logic, this can lead to confusing behaviors - e.g.
> -	 * scheduling position not being updated across a priority change.
> -	 */
> -	void (*dequeue)(struct task_struct *p, u64 deq_flags);
> -
> -	/**
> -	 * @dispatch: Dispatch tasks from the BPF scheduler and/or user DSQs
> -	 * @cpu: CPU to dispatch tasks for
> -	 * @prev: previous task being switched out
> -	 *
> -	 * Called when a CPU's local dsq is empty. The operation should dispatch
> -	 * one or more tasks from the BPF scheduler into the DSQs using
> -	 * scx_bpf_dsq_insert() and/or move from user DSQs into the local DSQ
> -	 * using scx_bpf_dsq_move_to_local().
> -	 *
> -	 * The maximum number of times scx_bpf_dsq_insert() can be called
> -	 * without an intervening scx_bpf_dsq_move_to_local() is specified by
> -	 * ops.dispatch_max_batch. See the comments on top of the two functions
> -	 * for more details.
> -	 *
> -	 * When not %NULL, @prev is an SCX task with its slice depleted. If
> -	 * @prev is still runnable as indicated by set %SCX_TASK_QUEUED in
> -	 * @prev->scx.flags, it is not enqueued yet and will be enqueued after
> -	 * ops.dispatch() returns. To keep executing @prev, return without
> -	 * dispatching or moving any tasks. Also see %SCX_OPS_ENQ_LAST.
> -	 */
> -	void (*dispatch)(s32 cpu, struct task_struct *prev);
> -
> -	/**
> -	 * @tick: Periodic tick
> -	 * @p: task running currently
> -	 *
> -	 * This operation is called every 1/HZ seconds on CPUs which are
> -	 * executing an SCX task. Setting @p->scx.slice to 0 will trigger an
> -	 * immediate dispatch cycle on the CPU.
> -	 */
> -	void (*tick)(struct task_struct *p);
> -
> -	/**
> -	 * @runnable: A task is becoming runnable on its associated CPU
> -	 * @p: task becoming runnable
> -	 * @enq_flags: %SCX_ENQ_*
> -	 *
> -	 * This and the following three functions can be used to track a task's
> -	 * execution state transitions. A task becomes ->runnable() on a CPU,
> -	 * and then goes through one or more ->running() and ->stopping() pairs
> -	 * as it runs on the CPU, and eventually becomes ->quiescent() when it's
> -	 * done running on the CPU.
> -	 *
> -	 * @p is becoming runnable on the CPU because it's
> -	 *
> -	 * - waking up (%SCX_ENQ_WAKEUP)
> -	 * - being moved from another CPU
> -	 * - being restored after temporarily taken off the queue for an
> -	 *   attribute change.
> -	 *
> -	 * This and ->enqueue() are related but not coupled. This operation
> -	 * notifies @p's state transition and may not be followed by ->enqueue()
> -	 * e.g. when @p is being dispatched to a remote CPU, or when @p is
> -	 * being enqueued on a CPU experiencing a hotplug event. Likewise, a
> -	 * task may be ->enqueue()'d without being preceded by this operation
> -	 * e.g. after exhausting its slice.
> -	 */
> -	void (*runnable)(struct task_struct *p, u64 enq_flags);
> -
> -	/**
> -	 * @running: A task is starting to run on its associated CPU
> -	 * @p: task starting to run
> -	 *
> -	 * Note that this callback may be called from a CPU other than the
> -	 * one the task is going to run on. This can happen when a task
> -	 * property is changed (i.e., affinity), since scx_next_task_scx(),
> -	 * which triggers this callback, may run on a CPU different from
> -	 * the task's assigned CPU.
> -	 *
> -	 * Therefore, always use scx_bpf_task_cpu(@p) to determine the
> -	 * target CPU the task is going to use.
> -	 *
> -	 * See ->runnable() for explanation on the task state notifiers.
> -	 */
> -	void (*running)(struct task_struct *p);
> -
> -	/**
> -	 * @stopping: A task is stopping execution
> -	 * @p: task stopping to run
> -	 * @runnable: is task @p still runnable?
> -	 *
> -	 * Note that this callback may be called from a CPU other than the
> -	 * one the task was running on. This can happen when a task
> -	 * property is changed (i.e., affinity), since dequeue_task_scx(),
> -	 * which triggers this callback, may run on a CPU different from
> -	 * the task's assigned CPU.
> -	 *
> -	 * Therefore, always use scx_bpf_task_cpu(@p) to retrieve the CPU
> -	 * the task was running on.
> -	 *
> -	 * See ->runnable() for explanation on the task state notifiers. If
> -	 * !@runnable, ->quiescent() will be invoked after this operation
> -	 * returns.
> -	 */
> -	void (*stopping)(struct task_struct *p, bool runnable);
> -
> -	/**
> -	 * @quiescent: A task is becoming not runnable on its associated CPU
> -	 * @p: task becoming not runnable
> -	 * @deq_flags: %SCX_DEQ_*
> -	 *
> -	 * See ->runnable() for explanation on the task state notifiers.
> -	 *
> -	 * @p is becoming quiescent on the CPU because it's
> -	 *
> -	 * - sleeping (%SCX_DEQ_SLEEP)
> -	 * - being moved to another CPU
> -	 * - being temporarily taken off the queue for an attribute change
> -	 *   (%SCX_DEQ_SAVE)
> -	 *
> -	 * This and ->dequeue() are related but not coupled. This operation
> -	 * notifies @p's state transition and may not be preceded by ->dequeue()
> -	 * e.g. when @p is being dispatched to a remote CPU.
> -	 */
> -	void (*quiescent)(struct task_struct *p, u64 deq_flags);
> -
> -	/**
> -	 * @yield: Yield CPU
> -	 * @from: yielding task
> -	 * @to: optional yield target task
> -	 *
> -	 * If @to is NULL, @from is yielding the CPU to other runnable tasks.
> -	 * The BPF scheduler should ensure that other available tasks are
> -	 * dispatched before the yielding task. Return value is ignored in this
> -	 * case.
> -	 *
> -	 * If @to is not-NULL, @from wants to yield the CPU to @to. If the bpf
> -	 * scheduler can implement the request, return %true; otherwise, %false.
> -	 */
> -	bool (*yield)(struct task_struct *from, struct task_struct *to);
> -
> -	/**
> -	 * @core_sched_before: Task ordering for core-sched
> -	 * @a: task A
> -	 * @b: task B
> -	 *
> -	 * Used by core-sched to determine the ordering between two tasks. See
> -	 * Documentation/admin-guide/hw-vuln/core-scheduling.rst for details on
> -	 * core-sched.
> -	 *
> -	 * Both @a and @b are runnable and may or may not currently be queued on
> -	 * the BPF scheduler. Should return %true if @a should run before @b.
> -	 * %false if there's no required ordering or @b should run before @a.
> -	 *
> -	 * If not specified, the default is ordering them according to when they
> -	 * became runnable.
> -	 */
> -	bool (*core_sched_before)(struct task_struct *a, struct task_struct *b);
> -
> -	/**
> -	 * @set_weight: Set task weight
> -	 * @p: task to set weight for
> -	 * @weight: new weight [1..10000]
> -	 *
> -	 * Update @p's weight to @weight.
> -	 */
> -	void (*set_weight)(struct task_struct *p, u32 weight);
> -
> -	/**
> -	 * @set_cpumask: Set CPU affinity
> -	 * @p: task to set CPU affinity for
> -	 * @cpumask: cpumask of cpus that @p can run on
> -	 *
> -	 * Update @p's CPU affinity to @cpumask.
> -	 */
> -	void (*set_cpumask)(struct task_struct *p,
> -			    const struct cpumask *cpumask);
> -
> -	/**
> -	 * @update_idle: Update the idle state of a CPU
> -	 * @cpu: CPU to update the idle state for
> -	 * @idle: whether entering or exiting the idle state
> -	 *
> -	 * This operation is called when @rq's CPU goes or leaves the idle
> -	 * state. By default, implementing this operation disables the built-in
> -	 * idle CPU tracking and the following helpers become unavailable:
> -	 *
> -	 * - scx_bpf_select_cpu_dfl()
> -	 * - scx_bpf_select_cpu_and()
> -	 * - scx_bpf_test_and_clear_cpu_idle()
> -	 * - scx_bpf_pick_idle_cpu()
> -	 *
> -	 * The user also must implement ops.select_cpu() as the default
> -	 * implementation relies on scx_bpf_select_cpu_dfl().
> -	 *
> -	 * Specify the %SCX_OPS_KEEP_BUILTIN_IDLE flag to keep the built-in idle
> -	 * tracking.
> -	 */
> -	void (*update_idle)(s32 cpu, bool idle);
> -
> -	/**
> -	 * @cpu_acquire: A CPU is becoming available to the BPF scheduler
> -	 * @cpu: The CPU being acquired by the BPF scheduler.
> -	 * @args: Acquire arguments, see the struct definition.
> -	 *
> -	 * A CPU that was previously released from the BPF scheduler is now once
> -	 * again under its control.
> -	 */
> -	void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
> -
> -	/**
> -	 * @cpu_release: A CPU is taken away from the BPF scheduler
> -	 * @cpu: The CPU being released by the BPF scheduler.
> -	 * @args: Release arguments, see the struct definition.
> -	 *
> -	 * The specified CPU is no longer under the control of the BPF
> -	 * scheduler. This could be because it was preempted by a higher
> -	 * priority sched_class, though there may be other reasons as well. The
> -	 * caller should consult @args->reason to determine the cause.
> -	 */
> -	void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
> -
> -	/**
> -	 * @init_task: Initialize a task to run in a BPF scheduler
> -	 * @p: task to initialize for BPF scheduling
> -	 * @args: init arguments, see the struct definition
> -	 *
> -	 * Either we're loading a BPF scheduler or a new task is being forked.
> -	 * Initialize @p for BPF scheduling. This operation may block and can
> -	 * be used for allocations, and is called exactly once for a task.
> -	 *
> -	 * Return 0 for success, -errno for failure. An error return while
> -	 * loading will abort loading of the BPF scheduler. During a fork, it
> -	 * will abort that specific fork.
> -	 */
> -	s32 (*init_task)(struct task_struct *p, struct scx_init_task_args *args);
> -
> -	/**
> -	 * @exit_task: Exit a previously-running task from the system
> -	 * @p: task to exit
> -	 * @args: exit arguments, see the struct definition
> -	 *
> -	 * @p is exiting or the BPF scheduler is being unloaded. Perform any
> -	 * necessary cleanup for @p.
> -	 */
> -	void (*exit_task)(struct task_struct *p, struct scx_exit_task_args *args);
> -
> -	/**
> -	 * @enable: Enable BPF scheduling for a task
> -	 * @p: task to enable BPF scheduling for
> -	 *
> -	 * Enable @p for BPF scheduling. enable() is called on @p any time it
> -	 * enters SCX, and is always paired with a matching disable().
> -	 */
> -	void (*enable)(struct task_struct *p);
> -
> -	/**
> -	 * @disable: Disable BPF scheduling for a task
> -	 * @p: task to disable BPF scheduling for
> -	 *
> -	 * @p is exiting, leaving SCX or the BPF scheduler is being unloaded.
> -	 * Disable BPF scheduling for @p. A disable() call is always matched
> -	 * with a prior enable() call.
> -	 */
> -	void (*disable)(struct task_struct *p);
> -
> -	/**
> -	 * @dump: Dump BPF scheduler state on error
> -	 * @ctx: debug dump context
> -	 *
> -	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump.
> -	 */
> -	void (*dump)(struct scx_dump_ctx *ctx);
> -
> -	/**
> -	 * @dump_cpu: Dump BPF scheduler state for a CPU on error
> -	 * @ctx: debug dump context
> -	 * @cpu: CPU to generate debug dump for
> -	 * @idle: @cpu is currently idle without any runnable tasks
> -	 *
> -	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
> -	 * @cpu. If @idle is %true and this operation doesn't produce any
> -	 * output, @cpu is skipped for dump.
> -	 */
> -	void (*dump_cpu)(struct scx_dump_ctx *ctx, s32 cpu, bool idle);
> -
> -	/**
> -	 * @dump_task: Dump BPF scheduler state for a runnable task on error
> -	 * @ctx: debug dump context
> -	 * @p: runnable task to generate debug dump for
> -	 *
> -	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
> -	 * @p.
> -	 */
> -	void (*dump_task)(struct scx_dump_ctx *ctx, struct task_struct *p);
> -
> -#ifdef CONFIG_EXT_GROUP_SCHED
> -	/**
> -	 * @cgroup_init: Initialize a cgroup
> -	 * @cgrp: cgroup being initialized
> -	 * @args: init arguments, see the struct definition
> -	 *
> -	 * Either the BPF scheduler is being loaded or @cgrp created, initialize
> -	 * @cgrp for sched_ext. This operation may block.
> -	 *
> -	 * Return 0 for success, -errno for failure. An error return while
> -	 * loading will abort loading of the BPF scheduler. During cgroup
> -	 * creation, it will abort the specific cgroup creation.
> -	 */
> -	s32 (*cgroup_init)(struct cgroup *cgrp,
> -			   struct scx_cgroup_init_args *args);
> -
> -	/**
> -	 * @cgroup_exit: Exit a cgroup
> -	 * @cgrp: cgroup being exited
> -	 *
> -	 * Either the BPF scheduler is being unloaded or @cgrp destroyed, exit
> -	 * @cgrp for sched_ext. This operation my block.
> -	 */
> -	void (*cgroup_exit)(struct cgroup *cgrp);
> -
> -	/**
> -	 * @cgroup_prep_move: Prepare a task to be moved to a different cgroup
> -	 * @p: task being moved
> -	 * @from: cgroup @p is being moved from
> -	 * @to: cgroup @p is being moved to
> -	 *
> -	 * Prepare @p for move from cgroup @from to @to. This operation may
> -	 * block and can be used for allocations.
> -	 *
> -	 * Return 0 for success, -errno for failure. An error return aborts the
> -	 * migration.
> -	 */
> -	s32 (*cgroup_prep_move)(struct task_struct *p,
> -				struct cgroup *from, struct cgroup *to);
> -
> -	/**
> -	 * @cgroup_move: Commit cgroup move
> -	 * @p: task being moved
> -	 * @from: cgroup @p is being moved from
> -	 * @to: cgroup @p is being moved to
> -	 *
> -	 * Commit the move. @p is dequeued during this operation.
> -	 */
> -	void (*cgroup_move)(struct task_struct *p,
> -			    struct cgroup *from, struct cgroup *to);
> -
> -	/**
> -	 * @cgroup_cancel_move: Cancel cgroup move
> -	 * @p: task whose cgroup move is being canceled
> -	 * @from: cgroup @p was being moved from
> -	 * @to: cgroup @p was being moved to
> -	 *
> -	 * @p was cgroup_prep_move()'d but failed before reaching cgroup_move().
> -	 * Undo the preparation.
> -	 */
> -	void (*cgroup_cancel_move)(struct task_struct *p,
> -				   struct cgroup *from, struct cgroup *to);
> -
> -	/**
> -	 * @cgroup_set_weight: A cgroup's weight is being changed
> -	 * @cgrp: cgroup whose weight is being updated
> -	 * @weight: new weight [1..10000]
> -	 *
> -	 * Update @cgrp's weight to @weight.
> -	 */
> -	void (*cgroup_set_weight)(struct cgroup *cgrp, u32 weight);
> -
> -	/**
> -	 * @cgroup_set_bandwidth: A cgroup's bandwidth is being changed
> -	 * @cgrp: cgroup whose bandwidth is being updated
> -	 * @period_us: bandwidth control period
> -	 * @quota_us: bandwidth control quota
> -	 * @burst_us: bandwidth control burst
> -	 *
> -	 * Update @cgrp's bandwidth control parameters. This is from the cpu.max
> -	 * cgroup interface.
> -	 *
> -	 * @quota_us / @period_us determines the CPU bandwidth @cgrp is entitled
> -	 * to. For example, if @period_us is 1_000_000 and @quota_us is
> -	 * 2_500_000. @cgrp is entitled to 2.5 CPUs. @burst_us can be
> -	 * interpreted in the same fashion and specifies how much @cgrp can
> -	 * burst temporarily. The specific control mechanism and thus the
> -	 * interpretation of @period_us and burstiness is upto to the BPF
> -	 * scheduler.
> -	 */
> -	void (*cgroup_set_bandwidth)(struct cgroup *cgrp,
> -				     u64 period_us, u64 quota_us, u64 burst_us);
> -
> -#endif	/* CONFIG_EXT_GROUP_SCHED */
> -
> -	/*
> -	 * All online ops must come before ops.cpu_online().
> -	 */
> -
> -	/**
> -	 * @cpu_online: A CPU became online
> -	 * @cpu: CPU which just came up
> -	 *
> -	 * @cpu just came online. @cpu will not call ops.enqueue() or
> -	 * ops.dispatch(), nor run tasks associated with other CPUs beforehand.
> -	 */
> -	void (*cpu_online)(s32 cpu);
> -
> -	/**
> -	 * @cpu_offline: A CPU is going offline
> -	 * @cpu: CPU which is going offline
> -	 *
> -	 * @cpu is going offline. @cpu will not call ops.enqueue() or
> -	 * ops.dispatch(), nor run tasks associated with other CPUs afterwards.
> -	 */
> -	void (*cpu_offline)(s32 cpu);
> -
> -	/*
> -	 * All CPU hotplug ops must come before ops.init().
> -	 */
> -
> -	/**
> -	 * @init: Initialize the BPF scheduler
> -	 */
> -	s32 (*init)(void);
> -
> -	/**
> -	 * @exit: Clean up after the BPF scheduler
> -	 * @info: Exit info
> -	 *
> -	 * ops.exit() is also called on ops.init() failure, which is a bit
> -	 * unusual. This is to allow rich reporting through @info on how
> -	 * ops.init() failed.
> -	 */
> -	void (*exit)(struct scx_exit_info *info);
> -
> -	/**
> -	 * @dispatch_max_batch: Max nr of tasks that dispatch() can dispatch
> -	 */
> -	u32 dispatch_max_batch;
> -
> -	/**
> -	 * @flags: %SCX_OPS_* flags
> -	 */
> -	u64 flags;
> -
> -	/**
> -	 * @timeout_ms: The maximum amount of time, in milliseconds, that a
> -	 * runnable task should be able to wait before being scheduled. The
> -	 * maximum timeout may not exceed the default timeout of 30 seconds.
> -	 *
> -	 * Defaults to the maximum allowed timeout value of 30 seconds.
> -	 */
> -	u32 timeout_ms;
> -
> -	/**
> -	 * @exit_dump_len: scx_exit_info.dump buffer length. If 0, the default
> -	 * value of 32768 is used.
> -	 */
> -	u32 exit_dump_len;
> -
> -	/**
> -	 * @hotplug_seq: A sequence number that may be set by the scheduler to
> -	 * detect when a hotplug event has occurred during the loading process.
> -	 * If 0, no detection occurs. Otherwise, the scheduler will fail to
> -	 * load if the sequence number does not match @scx_hotplug_seq on the
> -	 * enable path.
> -	 */
> -	u64 hotplug_seq;
> -
> -	/**
> -	 * @name: BPF scheduler's name
> -	 *
> -	 * Must be a non-zero valid BPF object name including only isalnum(),
> -	 * '_' and '.' chars. Shows up in kernel.sched_ext_ops sysctl while the
> -	 * BPF scheduler is enabled.
> -	 */
> -	char name[SCX_OPS_NAME_LEN];
> -
> -	/* internal use only, must be NULL */
> -	void *priv;
> -};
> -
> -enum scx_opi {
> -	SCX_OPI_BEGIN			= 0,
> -	SCX_OPI_NORMAL_BEGIN		= 0,
> -	SCX_OPI_NORMAL_END		= SCX_OP_IDX(cpu_online),
> -	SCX_OPI_CPU_HOTPLUG_BEGIN	= SCX_OP_IDX(cpu_online),
> -	SCX_OPI_CPU_HOTPLUG_END		= SCX_OP_IDX(init),
> -	SCX_OPI_END			= SCX_OP_IDX(init),
> -};
> -
> -/*
> - * Collection of event counters. Event types are placed in descending order.
> - */
> -struct scx_event_stats {
> -	/*
> -	 * If ops.select_cpu() returns a CPU which can't be used by the task,
> -	 * the core scheduler code silently picks a fallback CPU.
> -	 */
> -	s64		SCX_EV_SELECT_CPU_FALLBACK;
> -
> -	/*
> -	 * When dispatching to a local DSQ, the CPU may have gone offline in
> -	 * the meantime. In this case, the task is bounced to the global DSQ.
> -	 */
> -	s64		SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE;
> -
> -	/*
> -	 * If SCX_OPS_ENQ_LAST is not set, the number of times that a task
> -	 * continued to run because there were no other tasks on the CPU.
> -	 */
> -	s64		SCX_EV_DISPATCH_KEEP_LAST;
> -
> -	/*
> -	 * If SCX_OPS_ENQ_EXITING is not set, the number of times that a task
> -	 * is dispatched to a local DSQ when exiting.
> -	 */
> -	s64		SCX_EV_ENQ_SKIP_EXITING;
> -
> -	/*
> -	 * If SCX_OPS_ENQ_MIGRATION_DISABLED is not set, the number of times a
> -	 * migration disabled task skips ops.enqueue() and is dispatched to its
> -	 * local DSQ.
> -	 */
> -	s64		SCX_EV_ENQ_SKIP_MIGRATION_DISABLED;
> -
> -	/*
> -	 * Total number of times a task's time slice was refilled with the
> -	 * default value (SCX_SLICE_DFL).
> -	 */
> -	s64		SCX_EV_REFILL_SLICE_DFL;
> -
> -	/*
> -	 * The total duration of bypass modes in nanoseconds.
> -	 */
> -	s64		SCX_EV_BYPASS_DURATION;
> -
> -	/*
> -	 * The number of tasks dispatched in the bypassing mode.
> -	 */
> -	s64		SCX_EV_BYPASS_DISPATCH;
> -
> -	/*
> -	 * The number of times the bypassing mode has been activated.
> -	 */
> -	s64		SCX_EV_BYPASS_ACTIVATE;
> -};
> -
> -struct scx_sched {
> -	struct sched_ext_ops	ops;
> -	DECLARE_BITMAP(has_op, SCX_OPI_END);
> -
> -	/*
> -	 * Dispatch queues.
> -	 *
> -	 * The global DSQ (%SCX_DSQ_GLOBAL) is split per-node for scalability.
> -	 * This is to avoid live-locking in bypass mode where all tasks are
> -	 * dispatched to %SCX_DSQ_GLOBAL and all CPUs consume from it. If
> -	 * per-node split isn't sufficient, it can be further split.
> -	 */
> -	struct rhashtable	dsq_hash;
> -	struct scx_dispatch_q	**global_dsqs;
> -
> -	/*
> -	 * The event counters are in a per-CPU variable to minimize the
> -	 * accounting overhead. A system-wide view on the event counter is
> -	 * constructed when requested by scx_bpf_events().
> -	 */
> -	struct scx_event_stats __percpu *event_stats_cpu;
> -
> -	bool			warned_zero_slice;
> -
> -	atomic_t		exit_kind;
> -	struct scx_exit_info	*exit_info;
> -
> -	struct kobject		kobj;
> -
> -	struct kthread_worker	*helper;
> -	struct irq_work		error_irq_work;
> -	struct kthread_work	disable_work;
> -	struct rcu_work		rcu_work;
> -};
> -
> -enum scx_wake_flags {
> -	/* expose select WF_* flags as enums */
> -	SCX_WAKE_FORK		= WF_FORK,
> -	SCX_WAKE_TTWU		= WF_TTWU,
> -	SCX_WAKE_SYNC		= WF_SYNC,
> -};
> -
> -enum scx_enq_flags {
> -	/* expose select ENQUEUE_* flags as enums */
> -	SCX_ENQ_WAKEUP		= ENQUEUE_WAKEUP,
> -	SCX_ENQ_HEAD		= ENQUEUE_HEAD,
> -	SCX_ENQ_CPU_SELECTED	= ENQUEUE_RQ_SELECTED,
> -
> -	/* high 32bits are SCX specific */
> -
> -	/*
> -	 * Set the following to trigger preemption when calling
> -	 * scx_bpf_dsq_insert() with a local dsq as the target. The slice of the
> -	 * current task is cleared to zero and the CPU is kicked into the
> -	 * scheduling path. Implies %SCX_ENQ_HEAD.
> -	 */
> -	SCX_ENQ_PREEMPT		= 1LLU << 32,
> -
> -	/*
> -	 * The task being enqueued was previously enqueued on the current CPU's
> -	 * %SCX_DSQ_LOCAL, but was removed from it in a call to the
> -	 * scx_bpf_reenqueue_local() kfunc. If scx_bpf_reenqueue_local() was
> -	 * invoked in a ->cpu_release() callback, and the task is again
> -	 * dispatched back to %SCX_LOCAL_DSQ by this current ->enqueue(), the
> -	 * task will not be scheduled on the CPU until at least the next invocation
> -	 * of the ->cpu_acquire() callback.
> -	 */
> -	SCX_ENQ_REENQ		= 1LLU << 40,
> -
> -	/*
> -	 * The task being enqueued is the only task available for the cpu. By
> -	 * default, ext core keeps executing such tasks but when
> -	 * %SCX_OPS_ENQ_LAST is specified, they're ops.enqueue()'d with the
> -	 * %SCX_ENQ_LAST flag set.
> -	 *
> -	 * The BPF scheduler is responsible for triggering a follow-up
> -	 * scheduling event. Otherwise, Execution may stall.
> -	 */
> -	SCX_ENQ_LAST		= 1LLU << 41,
> -
> -	/* high 8 bits are internal */
> -	__SCX_ENQ_INTERNAL_MASK	= 0xffLLU << 56,
> -
> -	SCX_ENQ_CLEAR_OPSS	= 1LLU << 56,
> -	SCX_ENQ_DSQ_PRIQ	= 1LLU << 57,
> -};
> -
> -enum scx_deq_flags {
> -	/* expose select DEQUEUE_* flags as enums */
> -	SCX_DEQ_SLEEP		= DEQUEUE_SLEEP,
> -
> -	/* high 32bits are SCX specific */
> -
> -	/*
> -	 * The generic core-sched layer decided to execute the task even though
> -	 * it hasn't been dispatched yet. Dequeue from the BPF side.
> -	 */
> -	SCX_DEQ_CORE_SCHED_EXEC	= 1LLU << 32,
> -};
> -
> -enum scx_pick_idle_cpu_flags {
> -	SCX_PICK_IDLE_CORE	= 1LLU << 0,	/* pick a CPU whose SMT siblings are also idle */
> -	SCX_PICK_IDLE_IN_NODE	= 1LLU << 1,	/* pick a CPU in the same target NUMA node */
> -};
> -
> -enum scx_kick_flags {
> -	/*
> -	 * Kick the target CPU if idle. Guarantees that the target CPU goes
> -	 * through at least one full scheduling cycle before going idle. If the
> -	 * target CPU can be determined to be currently not idle and going to go
> -	 * through a scheduling cycle before going idle, noop.
> -	 */
> -	SCX_KICK_IDLE		= 1LLU << 0,
> -
> -	/*
> -	 * Preempt the current task and execute the dispatch path. If the
> -	 * current task of the target CPU is an SCX task, its ->scx.slice is
> -	 * cleared to zero before the scheduling path is invoked so that the
> -	 * task expires and the dispatch path is invoked.
> -	 */
> -	SCX_KICK_PREEMPT	= 1LLU << 1,
> -
> -	/*
> -	 * Wait for the CPU to be rescheduled. The scx_bpf_kick_cpu() call will
> -	 * return after the target CPU finishes picking the next task.
> -	 */
> -	SCX_KICK_WAIT		= 1LLU << 2,
> -};
> -
> -enum scx_tg_flags {
> -	SCX_TG_ONLINE		= 1U << 0,
> -	SCX_TG_INITED		= 1U << 1,
> -};
> -
> -enum scx_enable_state {
> -	SCX_ENABLING,
> -	SCX_ENABLED,
> -	SCX_DISABLING,
> -	SCX_DISABLED,
> -};
> -
> -static const char *scx_enable_state_str[] = {
> -	[SCX_ENABLING]		= "enabling",
> -	[SCX_ENABLED]		= "enabled",
> -	[SCX_DISABLING]		= "disabling",
> -	[SCX_DISABLED]		= "disabled",
> -};
> -
> -/*
> - * sched_ext_entity->ops_state
> - *
> - * Used to track the task ownership between the SCX core and the BPF scheduler.
> - * State transitions look as follows:
> - *
> - * NONE -> QUEUEING -> QUEUED -> DISPATCHING
> - *   ^              |                 |
> - *   |              v                 v
> - *   \-------------------------------/
> - *
> - * QUEUEING and DISPATCHING states can be waited upon. See wait_ops_state() call
> - * sites for explanations on the conditions being waited upon and why they are
> - * safe. Transitions out of them into NONE or QUEUED must store_release and the
> - * waiters should load_acquire.
> - *
> - * Tracking scx_ops_state enables sched_ext core to reliably determine whether
> - * any given task can be dispatched by the BPF scheduler at all times and thus
> - * relaxes the requirements on the BPF scheduler. This allows the BPF scheduler
> - * to try to dispatch any task anytime regardless of its state as the SCX core
> - * can safely reject invalid dispatches.
> - */
> -enum scx_ops_state {
> -	SCX_OPSS_NONE,		/* owned by the SCX core */
> -	SCX_OPSS_QUEUEING,	/* in transit to the BPF scheduler */
> -	SCX_OPSS_QUEUED,	/* owned by the BPF scheduler */
> -	SCX_OPSS_DISPATCHING,	/* in transit back to the SCX core */
> -
> -	/*
> -	 * QSEQ brands each QUEUED instance so that, when dispatch races
> -	 * dequeue/requeue, the dispatcher can tell whether it still has a claim
> -	 * on the task being dispatched.
> -	 *
> -	 * As some 32bit archs can't do 64bit store_release/load_acquire,
> -	 * p->scx.ops_state is atomic_long_t which leaves 30 bits for QSEQ on
> -	 * 32bit machines. The dispatch race window QSEQ protects is very narrow
> -	 * and runs with IRQ disabled. 30 bits should be sufficient.
> -	 */
> -	SCX_OPSS_QSEQ_SHIFT	= 2,
> -};
> -
> -/* Use macros to ensure that the type is unsigned long for the masks */
> -#define SCX_OPSS_STATE_MASK	((1LU << SCX_OPSS_QSEQ_SHIFT) - 1)
> -#define SCX_OPSS_QSEQ_MASK	(~SCX_OPSS_STATE_MASK)
> -
>  /*
>   * NOTE: sched_ext is in the process of growing multiple scheduler support and
>   * scx_root usage is in a transitional state. Naked dereferences are safe if the
> diff --git a/kernel/sched/ext.h b/kernel/sched/ext.h
> index 292bb41a242e..33858607bc97 100644
> --- a/kernel/sched/ext.h
> +++ b/kernel/sched/ext.h
> @@ -8,29 +8,6 @@
>   */
>  #ifdef CONFIG_SCHED_CLASS_EXT
>  
> -static inline bool scx_kf_allowed_if_unlocked(void)
> -{
> -	return !current->scx.kf_mask;
> -}
> -
> -static inline bool scx_rq_bypassing(struct rq *rq)
> -{
> -	return unlikely(rq->scx.flags & SCX_RQ_BYPASSING);
> -}
> -
> -DECLARE_STATIC_KEY_FALSE(scx_ops_allow_queued_wakeup);
> -
> -DECLARE_PER_CPU(struct rq *, scx_locked_rq_state);
> -
> -/*
> - * Return the rq currently locked from an scx callback, or NULL if no rq is
> - * locked.
> - */
> -static inline struct rq *scx_locked_rq(void)
> -{
> -	return __this_cpu_read(scx_locked_rq_state);
> -}
> -
>  void scx_tick(struct rq *rq);
>  void init_scx_entity(struct sched_ext_entity *scx);
>  void scx_pre_fork(struct task_struct *p);
> diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
> new file mode 100644
> index 000000000000..76690ede8700
> --- /dev/null
> +++ b/kernel/sched/ext_internal.h
> @@ -0,0 +1,1061 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * BPF extensible scheduler class: Documentation/scheduler/sched-ext.rst
> + *
> + * Copyright (c) 2025 Meta Platforms, Inc. and affiliates.
> + * Copyright (c) 2025 Tejun Heo <tj@kernel.org>
> + */
> +#define SCX_OP_IDX(op)		(offsetof(struct sched_ext_ops, op) / sizeof(void (*)(void)))
> +
> +enum scx_consts {
> +	SCX_DSP_DFL_MAX_BATCH		= 32,
> +	SCX_DSP_MAX_LOOPS		= 32,
> +	SCX_WATCHDOG_MAX_TIMEOUT	= 30 * HZ,
> +
> +	SCX_EXIT_BT_LEN			= 64,
> +	SCX_EXIT_MSG_LEN		= 1024,
> +	SCX_EXIT_DUMP_DFL_LEN		= 32768,
> +
> +	SCX_CPUPERF_ONE			= SCHED_CAPACITY_SCALE,
> +
> +	/*
> +	 * Iterating all tasks may take a while. Periodically drop
> +	 * scx_tasks_lock to avoid causing e.g. CSD and RCU stalls.
> +	 */
> +	SCX_TASK_ITER_BATCH		= 32,
> +};
> +
> +enum scx_exit_kind {
> +	SCX_EXIT_NONE,
> +	SCX_EXIT_DONE,
> +
> +	SCX_EXIT_UNREG = 64,	/* user-space initiated unregistration */
> +	SCX_EXIT_UNREG_BPF,	/* BPF-initiated unregistration */
> +	SCX_EXIT_UNREG_KERN,	/* kernel-initiated unregistration */
> +	SCX_EXIT_SYSRQ,		/* requested by 'S' sysrq */
> +
> +	SCX_EXIT_ERROR = 1024,	/* runtime error, error msg contains details */
> +	SCX_EXIT_ERROR_BPF,	/* ERROR but triggered through scx_bpf_error() */
> +	SCX_EXIT_ERROR_STALL,	/* watchdog detected stalled runnable tasks */
> +};
> +
> +/*
> + * An exit code can be specified when exiting with scx_bpf_exit() or scx_exit(),
> + * corresponding to exit_kind UNREG_BPF and UNREG_KERN respectively. The codes
> + * are 64bit of the format:
> + *
> + *   Bits: [63  ..  48 47   ..  32 31 .. 0]
> + *         [ SYS ACT ] [ SYS RSN ] [ USR  ]
> + *
> + *   SYS ACT: System-defined exit actions
> + *   SYS RSN: System-defined exit reasons
> + *   USR    : User-defined exit codes and reasons
> + *
> + * Using the above, users may communicate intention and context by ORing system
> + * actions and/or system reasons with a user-defined exit code.
> + */
> +enum scx_exit_code {
> +	/* Reasons */
> +	SCX_ECODE_RSN_HOTPLUG	= 1LLU << 32,
> +
> +	/* Actions */
> +	SCX_ECODE_ACT_RESTART	= 1LLU << 48,
> +};
> +
> +/*
> + * scx_exit_info is passed to ops.exit() to describe why the BPF scheduler is
> + * being disabled.
> + */
> +struct scx_exit_info {
> +	/* %SCX_EXIT_* - broad category of the exit reason */
> +	enum scx_exit_kind	kind;
> +
> +	/* exit code if gracefully exiting */
> +	s64			exit_code;
> +
> +	/* textual representation of the above */
> +	const char		*reason;
> +
> +	/* backtrace if exiting due to an error */
> +	unsigned long		*bt;
> +	u32			bt_len;
> +
> +	/* informational message */
> +	char			*msg;
> +
> +	/* debug dump */
> +	char			*dump;
> +};
> +
> +/* sched_ext_ops.flags */
> +enum scx_ops_flags {
> +	/*
> +	 * Keep built-in idle tracking even if ops.update_idle() is implemented.
> +	 */
> +	SCX_OPS_KEEP_BUILTIN_IDLE	= 1LLU << 0,
> +
> +	/*
> +	 * By default, if there are no other task to run on the CPU, ext core
> +	 * keeps running the current task even after its slice expires. If this
> +	 * flag is specified, such tasks are passed to ops.enqueue() with
> +	 * %SCX_ENQ_LAST. See the comment above %SCX_ENQ_LAST for more info.
> +	 */
> +	SCX_OPS_ENQ_LAST		= 1LLU << 1,
> +
> +	/*
> +	 * An exiting task may schedule after PF_EXITING is set. In such cases,
> +	 * bpf_task_from_pid() may not be able to find the task and if the BPF
> +	 * scheduler depends on pid lookup for dispatching, the task will be
> +	 * lost leading to various issues including RCU grace period stalls.
> +	 *
> +	 * To mask this problem, by default, unhashed tasks are automatically
> +	 * dispatched to the local DSQ on enqueue. If the BPF scheduler doesn't
> +	 * depend on pid lookups and wants to handle these tasks directly, the
> +	 * following flag can be used.
> +	 */
> +	SCX_OPS_ENQ_EXITING		= 1LLU << 2,
> +
> +	/*
> +	 * If set, only tasks with policy set to SCHED_EXT are attached to
> +	 * sched_ext. If clear, SCHED_NORMAL tasks are also included.
> +	 */
> +	SCX_OPS_SWITCH_PARTIAL		= 1LLU << 3,
> +
> +	/*
> +	 * A migration disabled task can only execute on its current CPU. By
> +	 * default, such tasks are automatically put on the CPU's local DSQ with
> +	 * the default slice on enqueue. If this ops flag is set, they also go
> +	 * through ops.enqueue().
> +	 *
> +	 * A migration disabled task never invokes ops.select_cpu() as it can
> +	 * only select the current CPU. Also, p->cpus_ptr will only contain its
> +	 * current CPU while p->nr_cpus_allowed keeps tracking p->user_cpus_ptr
> +	 * and thus may disagree with cpumask_weight(p->cpus_ptr).
> +	 */
> +	SCX_OPS_ENQ_MIGRATION_DISABLED	= 1LLU << 4,
> +
> +	/*
> +	 * Queued wakeup (ttwu_queue) is a wakeup optimization that invokes
> +	 * ops.enqueue() on the ops.select_cpu() selected or the wakee's
> +	 * previous CPU via IPI (inter-processor interrupt) to reduce cacheline
> +	 * transfers. When this optimization is enabled, ops.select_cpu() is
> +	 * skipped in some cases (when racing against the wakee switching out).
> +	 * As the BPF scheduler may depend on ops.select_cpu() being invoked
> +	 * during wakeups, queued wakeup is disabled by default.
> +	 *
> +	 * If this ops flag is set, queued wakeup optimization is enabled and
> +	 * the BPF scheduler must be able to handle ops.enqueue() invoked on the
> +	 * wakee's CPU without preceding ops.select_cpu() even for tasks which
> +	 * may be executed on multiple CPUs.
> +	 */
> +	SCX_OPS_ALLOW_QUEUED_WAKEUP	= 1LLU << 5,
> +
> +	/*
> +	 * If set, enable per-node idle cpumasks. If clear, use a single global
> +	 * flat idle cpumask.
> +	 */
> +	SCX_OPS_BUILTIN_IDLE_PER_NODE	= 1LLU << 6,
> +
> +	/*
> +	 * CPU cgroup support flags
> +	 */
> +	SCX_OPS_HAS_CGROUP_WEIGHT	= 1LLU << 16,	/* DEPRECATED, will be removed on 6.18 */
> +
> +	SCX_OPS_ALL_FLAGS		= SCX_OPS_KEEP_BUILTIN_IDLE |
> +					  SCX_OPS_ENQ_LAST |
> +					  SCX_OPS_ENQ_EXITING |
> +					  SCX_OPS_ENQ_MIGRATION_DISABLED |
> +					  SCX_OPS_ALLOW_QUEUED_WAKEUP |
> +					  SCX_OPS_SWITCH_PARTIAL |
> +					  SCX_OPS_BUILTIN_IDLE_PER_NODE |
> +					  SCX_OPS_HAS_CGROUP_WEIGHT,
> +
> +	/* high 8 bits are internal, don't include in SCX_OPS_ALL_FLAGS */
> +	__SCX_OPS_INTERNAL_MASK		= 0xffLLU << 56,
> +
> +	SCX_OPS_HAS_CPU_PREEMPT		= 1LLU << 56,
> +};
> +
> +/* argument container for ops.init_task() */
> +struct scx_init_task_args {
> +	/*
> +	 * Set if ops.init_task() is being invoked on the fork path, as opposed
> +	 * to the scheduler transition path.
> +	 */
> +	bool			fork;
> +#ifdef CONFIG_EXT_GROUP_SCHED
> +	/* the cgroup the task is joining */
> +	struct cgroup		*cgroup;
> +#endif
> +};
> +
> +/* argument container for ops.exit_task() */
> +struct scx_exit_task_args {
> +	/* Whether the task exited before running on sched_ext. */
> +	bool cancelled;
> +};
> +
> +/* argument container for ops->cgroup_init() */
> +struct scx_cgroup_init_args {
> +	/* the weight of the cgroup [1..10000] */
> +	u32			weight;
> +
> +	/* bandwidth control parameters from cpu.max and cpu.max.burst */
> +	u64			bw_period_us;
> +	u64			bw_quota_us;
> +	u64			bw_burst_us;
> +};
> +
> +enum scx_cpu_preempt_reason {
> +	/* next task is being scheduled by &sched_class_rt */
> +	SCX_CPU_PREEMPT_RT,
> +	/* next task is being scheduled by &sched_class_dl */
> +	SCX_CPU_PREEMPT_DL,
> +	/* next task is being scheduled by &sched_class_stop */
> +	SCX_CPU_PREEMPT_STOP,
> +	/* unknown reason for SCX being preempted */
> +	SCX_CPU_PREEMPT_UNKNOWN,
> +};
> +
> +/*
> + * Argument container for ops->cpu_acquire(). Currently empty, but may be
> + * expanded in the future.
> + */
> +struct scx_cpu_acquire_args {};
> +
> +/* argument container for ops->cpu_release() */
> +struct scx_cpu_release_args {
> +	/* the reason the CPU was preempted */
> +	enum scx_cpu_preempt_reason reason;
> +
> +	/* the task that's going to be scheduled on the CPU */
> +	struct task_struct	*task;
> +};
> +
> +/*
> + * Informational context provided to dump operations.
> + */
> +struct scx_dump_ctx {
> +	enum scx_exit_kind	kind;
> +	s64			exit_code;
> +	const char		*reason;
> +	u64			at_ns;
> +	u64			at_jiffies;
> +};
> +
> +/**
> + * struct sched_ext_ops - Operation table for BPF scheduler implementation
> + *
> + * A BPF scheduler can implement an arbitrary scheduling policy by
> + * implementing and loading operations in this table. Note that a userland
> + * scheduling policy can also be implemented using the BPF scheduler
> + * as a shim layer.
> + */
> +struct sched_ext_ops {
> +	/**
> +	 * @select_cpu: Pick the target CPU for a task which is being woken up
> +	 * @p: task being woken up
> +	 * @prev_cpu: the cpu @p was on before sleeping
> +	 * @wake_flags: SCX_WAKE_*
> +	 *
> +	 * Decision made here isn't final. @p may be moved to any CPU while it
> +	 * is getting dispatched for execution later. However, as @p is not on
> +	 * the rq at this point, getting the eventual execution CPU right here
> +	 * saves a small bit of overhead down the line.
> +	 *
> +	 * If an idle CPU is returned, the CPU is kicked and will try to
> +	 * dispatch. While an explicit custom mechanism can be added,
> +	 * select_cpu() serves as the default way to wake up idle CPUs.
> +	 *
> +	 * @p may be inserted into a DSQ directly by calling
> +	 * scx_bpf_dsq_insert(). If so, the ops.enqueue() will be skipped.
> +	 * Directly inserting into %SCX_DSQ_LOCAL will put @p in the local DSQ
> +	 * of the CPU returned by this operation.
> +	 *
> +	 * Note that select_cpu() is never called for tasks that can only run
> +	 * on a single CPU or tasks with migration disabled, as they don't have
> +	 * the option to select a different CPU. See select_task_rq() for
> +	 * details.
> +	 */
> +	s32 (*select_cpu)(struct task_struct *p, s32 prev_cpu, u64 wake_flags);
> +
> +	/**
> +	 * @enqueue: Enqueue a task on the BPF scheduler
> +	 * @p: task being enqueued
> +	 * @enq_flags: %SCX_ENQ_*
> +	 *
> +	 * @p is ready to run. Insert directly into a DSQ by calling
> +	 * scx_bpf_dsq_insert() or enqueue on the BPF scheduler. If not directly
> +	 * inserted, the bpf scheduler owns @p and if it fails to dispatch @p,
> +	 * the task will stall.
> +	 *
> +	 * If @p was inserted into a DSQ from ops.select_cpu(), this callback is
> +	 * skipped.
> +	 */
> +	void (*enqueue)(struct task_struct *p, u64 enq_flags);
> +
> +	/**
> +	 * @dequeue: Remove a task from the BPF scheduler
> +	 * @p: task being dequeued
> +	 * @deq_flags: %SCX_DEQ_*
> +	 *
> +	 * Remove @p from the BPF scheduler. This is usually called to isolate
> +	 * the task while updating its scheduling properties (e.g. priority).
> +	 *
> +	 * The ext core keeps track of whether the BPF side owns a given task or
> +	 * not and can gracefully ignore spurious dispatches from BPF side,
> +	 * which makes it safe to not implement this method. However, depending
> +	 * on the scheduling logic, this can lead to confusing behaviors - e.g.
> +	 * scheduling position not being updated across a priority change.
> +	 */
> +	void (*dequeue)(struct task_struct *p, u64 deq_flags);
> +
> +	/**
> +	 * @dispatch: Dispatch tasks from the BPF scheduler and/or user DSQs
> +	 * @cpu: CPU to dispatch tasks for
> +	 * @prev: previous task being switched out
> +	 *
> +	 * Called when a CPU's local dsq is empty. The operation should dispatch
> +	 * one or more tasks from the BPF scheduler into the DSQs using
> +	 * scx_bpf_dsq_insert() and/or move from user DSQs into the local DSQ
> +	 * using scx_bpf_dsq_move_to_local().
> +	 *
> +	 * The maximum number of times scx_bpf_dsq_insert() can be called
> +	 * without an intervening scx_bpf_dsq_move_to_local() is specified by
> +	 * ops.dispatch_max_batch. See the comments on top of the two functions
> +	 * for more details.
> +	 *
> +	 * When not %NULL, @prev is an SCX task with its slice depleted. If
> +	 * @prev is still runnable as indicated by set %SCX_TASK_QUEUED in
> +	 * @prev->scx.flags, it is not enqueued yet and will be enqueued after
> +	 * ops.dispatch() returns. To keep executing @prev, return without
> +	 * dispatching or moving any tasks. Also see %SCX_OPS_ENQ_LAST.
> +	 */
> +	void (*dispatch)(s32 cpu, struct task_struct *prev);
> +
> +	/**
> +	 * @tick: Periodic tick
> +	 * @p: task running currently
> +	 *
> +	 * This operation is called every 1/HZ seconds on CPUs which are
> +	 * executing an SCX task. Setting @p->scx.slice to 0 will trigger an
> +	 * immediate dispatch cycle on the CPU.
> +	 */
> +	void (*tick)(struct task_struct *p);
> +
> +	/**
> +	 * @runnable: A task is becoming runnable on its associated CPU
> +	 * @p: task becoming runnable
> +	 * @enq_flags: %SCX_ENQ_*
> +	 *
> +	 * This and the following three functions can be used to track a task's
> +	 * execution state transitions. A task becomes ->runnable() on a CPU,
> +	 * and then goes through one or more ->running() and ->stopping() pairs
> +	 * as it runs on the CPU, and eventually becomes ->quiescent() when it's
> +	 * done running on the CPU.
> +	 *
> +	 * @p is becoming runnable on the CPU because it's
> +	 *
> +	 * - waking up (%SCX_ENQ_WAKEUP)
> +	 * - being moved from another CPU
> +	 * - being restored after temporarily taken off the queue for an
> +	 *   attribute change.
> +	 *
> +	 * This and ->enqueue() are related but not coupled. This operation
> +	 * notifies @p's state transition and may not be followed by ->enqueue()
> +	 * e.g. when @p is being dispatched to a remote CPU, or when @p is
> +	 * being enqueued on a CPU experiencing a hotplug event. Likewise, a
> +	 * task may be ->enqueue()'d without being preceded by this operation
> +	 * e.g. after exhausting its slice.
> +	 */
> +	void (*runnable)(struct task_struct *p, u64 enq_flags);
> +
> +	/**
> +	 * @running: A task is starting to run on its associated CPU
> +	 * @p: task starting to run
> +	 *
> +	 * Note that this callback may be called from a CPU other than the
> +	 * one the task is going to run on. This can happen when a task
> +	 * property is changed (i.e., affinity), since scx_next_task_scx(),
> +	 * which triggers this callback, may run on a CPU different from
> +	 * the task's assigned CPU.
> +	 *
> +	 * Therefore, always use scx_bpf_task_cpu(@p) to determine the
> +	 * target CPU the task is going to use.
> +	 *
> +	 * See ->runnable() for explanation on the task state notifiers.
> +	 */
> +	void (*running)(struct task_struct *p);
> +
> +	/**
> +	 * @stopping: A task is stopping execution
> +	 * @p: task stopping to run
> +	 * @runnable: is task @p still runnable?
> +	 *
> +	 * Note that this callback may be called from a CPU other than the
> +	 * one the task was running on. This can happen when a task
> +	 * property is changed (i.e., affinity), since dequeue_task_scx(),
> +	 * which triggers this callback, may run on a CPU different from
> +	 * the task's assigned CPU.
> +	 *
> +	 * Therefore, always use scx_bpf_task_cpu(@p) to retrieve the CPU
> +	 * the task was running on.
> +	 *
> +	 * See ->runnable() for explanation on the task state notifiers. If
> +	 * !@runnable, ->quiescent() will be invoked after this operation
> +	 * returns.
> +	 */
> +	void (*stopping)(struct task_struct *p, bool runnable);
> +
> +	/**
> +	 * @quiescent: A task is becoming not runnable on its associated CPU
> +	 * @p: task becoming not runnable
> +	 * @deq_flags: %SCX_DEQ_*
> +	 *
> +	 * See ->runnable() for explanation on the task state notifiers.
> +	 *
> +	 * @p is becoming quiescent on the CPU because it's
> +	 *
> +	 * - sleeping (%SCX_DEQ_SLEEP)
> +	 * - being moved to another CPU
> +	 * - being temporarily taken off the queue for an attribute change
> +	 *   (%SCX_DEQ_SAVE)
> +	 *
> +	 * This and ->dequeue() are related but not coupled. This operation
> +	 * notifies @p's state transition and may not be preceded by ->dequeue()
> +	 * e.g. when @p is being dispatched to a remote CPU.
> +	 */
> +	void (*quiescent)(struct task_struct *p, u64 deq_flags);
> +
> +	/**
> +	 * @yield: Yield CPU
> +	 * @from: yielding task
> +	 * @to: optional yield target task
> +	 *
> +	 * If @to is NULL, @from is yielding the CPU to other runnable tasks.
> +	 * The BPF scheduler should ensure that other available tasks are
> +	 * dispatched before the yielding task. Return value is ignored in this
> +	 * case.
> +	 *
> +	 * If @to is not-NULL, @from wants to yield the CPU to @to. If the bpf
> +	 * scheduler can implement the request, return %true; otherwise, %false.
> +	 */
> +	bool (*yield)(struct task_struct *from, struct task_struct *to);
> +
> +	/**
> +	 * @core_sched_before: Task ordering for core-sched
> +	 * @a: task A
> +	 * @b: task B
> +	 *
> +	 * Used by core-sched to determine the ordering between two tasks. See
> +	 * Documentation/admin-guide/hw-vuln/core-scheduling.rst for details on
> +	 * core-sched.
> +	 *
> +	 * Both @a and @b are runnable and may or may not currently be queued on
> +	 * the BPF scheduler. Should return %true if @a should run before @b.
> +	 * %false if there's no required ordering or @b should run before @a.
> +	 *
> +	 * If not specified, the default is ordering them according to when they
> +	 * became runnable.
> +	 */
> +	bool (*core_sched_before)(struct task_struct *a, struct task_struct *b);
> +
> +	/**
> +	 * @set_weight: Set task weight
> +	 * @p: task to set weight for
> +	 * @weight: new weight [1..10000]
> +	 *
> +	 * Update @p's weight to @weight.
> +	 */
> +	void (*set_weight)(struct task_struct *p, u32 weight);
> +
> +	/**
> +	 * @set_cpumask: Set CPU affinity
> +	 * @p: task to set CPU affinity for
> +	 * @cpumask: cpumask of cpus that @p can run on
> +	 *
> +	 * Update @p's CPU affinity to @cpumask.
> +	 */
> +	void (*set_cpumask)(struct task_struct *p,
> +			    const struct cpumask *cpumask);
> +
> +	/**
> +	 * @update_idle: Update the idle state of a CPU
> +	 * @cpu: CPU to update the idle state for
> +	 * @idle: whether entering or exiting the idle state
> +	 *
> +	 * This operation is called when @rq's CPU goes or leaves the idle
> +	 * state. By default, implementing this operation disables the built-in
> +	 * idle CPU tracking and the following helpers become unavailable:
> +	 *
> +	 * - scx_bpf_select_cpu_dfl()
> +	 * - scx_bpf_select_cpu_and()
> +	 * - scx_bpf_test_and_clear_cpu_idle()
> +	 * - scx_bpf_pick_idle_cpu()
> +	 *
> +	 * The user also must implement ops.select_cpu() as the default
> +	 * implementation relies on scx_bpf_select_cpu_dfl().
> +	 *
> +	 * Specify the %SCX_OPS_KEEP_BUILTIN_IDLE flag to keep the built-in idle
> +	 * tracking.
> +	 */
> +	void (*update_idle)(s32 cpu, bool idle);
> +
> +	/**
> +	 * @cpu_acquire: A CPU is becoming available to the BPF scheduler
> +	 * @cpu: The CPU being acquired by the BPF scheduler.
> +	 * @args: Acquire arguments, see the struct definition.
> +	 *
> +	 * A CPU that was previously released from the BPF scheduler is now once
> +	 * again under its control.
> +	 */
> +	void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
> +
> +	/**
> +	 * @cpu_release: A CPU is taken away from the BPF scheduler
> +	 * @cpu: The CPU being released by the BPF scheduler.
> +	 * @args: Release arguments, see the struct definition.
> +	 *
> +	 * The specified CPU is no longer under the control of the BPF
> +	 * scheduler. This could be because it was preempted by a higher
> +	 * priority sched_class, though there may be other reasons as well. The
> +	 * caller should consult @args->reason to determine the cause.
> +	 */
> +	void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
> +
> +	/**
> +	 * @init_task: Initialize a task to run in a BPF scheduler
> +	 * @p: task to initialize for BPF scheduling
> +	 * @args: init arguments, see the struct definition
> +	 *
> +	 * Either we're loading a BPF scheduler or a new task is being forked.
> +	 * Initialize @p for BPF scheduling. This operation may block and can
> +	 * be used for allocations, and is called exactly once for a task.
> +	 *
> +	 * Return 0 for success, -errno for failure. An error return while
> +	 * loading will abort loading of the BPF scheduler. During a fork, it
> +	 * will abort that specific fork.
> +	 */
> +	s32 (*init_task)(struct task_struct *p, struct scx_init_task_args *args);
> +
> +	/**
> +	 * @exit_task: Exit a previously-running task from the system
> +	 * @p: task to exit
> +	 * @args: exit arguments, see the struct definition
> +	 *
> +	 * @p is exiting or the BPF scheduler is being unloaded. Perform any
> +	 * necessary cleanup for @p.
> +	 */
> +	void (*exit_task)(struct task_struct *p, struct scx_exit_task_args *args);
> +
> +	/**
> +	 * @enable: Enable BPF scheduling for a task
> +	 * @p: task to enable BPF scheduling for
> +	 *
> +	 * Enable @p for BPF scheduling. enable() is called on @p any time it
> +	 * enters SCX, and is always paired with a matching disable().
> +	 */
> +	void (*enable)(struct task_struct *p);
> +
> +	/**
> +	 * @disable: Disable BPF scheduling for a task
> +	 * @p: task to disable BPF scheduling for
> +	 *
> +	 * @p is exiting, leaving SCX or the BPF scheduler is being unloaded.
> +	 * Disable BPF scheduling for @p. A disable() call is always matched
> +	 * with a prior enable() call.
> +	 */
> +	void (*disable)(struct task_struct *p);
> +
> +	/**
> +	 * @dump: Dump BPF scheduler state on error
> +	 * @ctx: debug dump context
> +	 *
> +	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump.
> +	 */
> +	void (*dump)(struct scx_dump_ctx *ctx);
> +
> +	/**
> +	 * @dump_cpu: Dump BPF scheduler state for a CPU on error
> +	 * @ctx: debug dump context
> +	 * @cpu: CPU to generate debug dump for
> +	 * @idle: @cpu is currently idle without any runnable tasks
> +	 *
> +	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
> +	 * @cpu. If @idle is %true and this operation doesn't produce any
> +	 * output, @cpu is skipped for dump.
> +	 */
> +	void (*dump_cpu)(struct scx_dump_ctx *ctx, s32 cpu, bool idle);
> +
> +	/**
> +	 * @dump_task: Dump BPF scheduler state for a runnable task on error
> +	 * @ctx: debug dump context
> +	 * @p: runnable task to generate debug dump for
> +	 *
> +	 * Use scx_bpf_dump() to generate BPF scheduler specific debug dump for
> +	 * @p.
> +	 */
> +	void (*dump_task)(struct scx_dump_ctx *ctx, struct task_struct *p);
> +
> +#ifdef CONFIG_EXT_GROUP_SCHED
> +	/**
> +	 * @cgroup_init: Initialize a cgroup
> +	 * @cgrp: cgroup being initialized
> +	 * @args: init arguments, see the struct definition
> +	 *
> +	 * Either the BPF scheduler is being loaded or @cgrp created, initialize
> +	 * @cgrp for sched_ext. This operation may block.
> +	 *
> +	 * Return 0 for success, -errno for failure. An error return while
> +	 * loading will abort loading of the BPF scheduler. During cgroup
> +	 * creation, it will abort the specific cgroup creation.
> +	 */
> +	s32 (*cgroup_init)(struct cgroup *cgrp,
> +			   struct scx_cgroup_init_args *args);
> +
> +	/**
> +	 * @cgroup_exit: Exit a cgroup
> +	 * @cgrp: cgroup being exited
> +	 *
> +	 * Either the BPF scheduler is being unloaded or @cgrp destroyed, exit
> +	 * @cgrp for sched_ext. This operation my block.
> +	 */
> +	void (*cgroup_exit)(struct cgroup *cgrp);
> +
> +	/**
> +	 * @cgroup_prep_move: Prepare a task to be moved to a different cgroup
> +	 * @p: task being moved
> +	 * @from: cgroup @p is being moved from
> +	 * @to: cgroup @p is being moved to
> +	 *
> +	 * Prepare @p for move from cgroup @from to @to. This operation may
> +	 * block and can be used for allocations.
> +	 *
> +	 * Return 0 for success, -errno for failure. An error return aborts the
> +	 * migration.
> +	 */
> +	s32 (*cgroup_prep_move)(struct task_struct *p,
> +				struct cgroup *from, struct cgroup *to);
> +
> +	/**
> +	 * @cgroup_move: Commit cgroup move
> +	 * @p: task being moved
> +	 * @from: cgroup @p is being moved from
> +	 * @to: cgroup @p is being moved to
> +	 *
> +	 * Commit the move. @p is dequeued during this operation.
> +	 */
> +	void (*cgroup_move)(struct task_struct *p,
> +			    struct cgroup *from, struct cgroup *to);
> +
> +	/**
> +	 * @cgroup_cancel_move: Cancel cgroup move
> +	 * @p: task whose cgroup move is being canceled
> +	 * @from: cgroup @p was being moved from
> +	 * @to: cgroup @p was being moved to
> +	 *
> +	 * @p was cgroup_prep_move()'d but failed before reaching cgroup_move().
> +	 * Undo the preparation.
> +	 */
> +	void (*cgroup_cancel_move)(struct task_struct *p,
> +				   struct cgroup *from, struct cgroup *to);
> +
> +	/**
> +	 * @cgroup_set_weight: A cgroup's weight is being changed
> +	 * @cgrp: cgroup whose weight is being updated
> +	 * @weight: new weight [1..10000]
> +	 *
> +	 * Update @cgrp's weight to @weight.
> +	 */
> +	void (*cgroup_set_weight)(struct cgroup *cgrp, u32 weight);
> +
> +	/**
> +	 * @cgroup_set_bandwidth: A cgroup's bandwidth is being changed
> +	 * @cgrp: cgroup whose bandwidth is being updated
> +	 * @period_us: bandwidth control period
> +	 * @quota_us: bandwidth control quota
> +	 * @burst_us: bandwidth control burst
> +	 *
> +	 * Update @cgrp's bandwidth control parameters. This is from the cpu.max
> +	 * cgroup interface.
> +	 *
> +	 * @quota_us / @period_us determines the CPU bandwidth @cgrp is entitled
> +	 * to. For example, if @period_us is 1_000_000 and @quota_us is
> +	 * 2_500_000. @cgrp is entitled to 2.5 CPUs. @burst_us can be
> +	 * interpreted in the same fashion and specifies how much @cgrp can
> +	 * burst temporarily. The specific control mechanism and thus the
> +	 * interpretation of @period_us and burstiness is upto to the BPF
> +	 * scheduler.
> +	 */
> +	void (*cgroup_set_bandwidth)(struct cgroup *cgrp,
> +				     u64 period_us, u64 quota_us, u64 burst_us);
> +
> +#endif	/* CONFIG_EXT_GROUP_SCHED */
> +
> +	/*
> +	 * All online ops must come before ops.cpu_online().
> +	 */
> +
> +	/**
> +	 * @cpu_online: A CPU became online
> +	 * @cpu: CPU which just came up
> +	 *
> +	 * @cpu just came online. @cpu will not call ops.enqueue() or
> +	 * ops.dispatch(), nor run tasks associated with other CPUs beforehand.
> +	 */
> +	void (*cpu_online)(s32 cpu);
> +
> +	/**
> +	 * @cpu_offline: A CPU is going offline
> +	 * @cpu: CPU which is going offline
> +	 *
> +	 * @cpu is going offline. @cpu will not call ops.enqueue() or
> +	 * ops.dispatch(), nor run tasks associated with other CPUs afterwards.
> +	 */
> +	void (*cpu_offline)(s32 cpu);
> +
> +	/*
> +	 * All CPU hotplug ops must come before ops.init().
> +	 */
> +
> +	/**
> +	 * @init: Initialize the BPF scheduler
> +	 */
> +	s32 (*init)(void);
> +
> +	/**
> +	 * @exit: Clean up after the BPF scheduler
> +	 * @info: Exit info
> +	 *
> +	 * ops.exit() is also called on ops.init() failure, which is a bit
> +	 * unusual. This is to allow rich reporting through @info on how
> +	 * ops.init() failed.
> +	 */
> +	void (*exit)(struct scx_exit_info *info);
> +
> +	/**
> +	 * @dispatch_max_batch: Max nr of tasks that dispatch() can dispatch
> +	 */
> +	u32 dispatch_max_batch;
> +
> +	/**
> +	 * @flags: %SCX_OPS_* flags
> +	 */
> +	u64 flags;
> +
> +	/**
> +	 * @timeout_ms: The maximum amount of time, in milliseconds, that a
> +	 * runnable task should be able to wait before being scheduled. The
> +	 * maximum timeout may not exceed the default timeout of 30 seconds.
> +	 *
> +	 * Defaults to the maximum allowed timeout value of 30 seconds.
> +	 */
> +	u32 timeout_ms;
> +
> +	/**
> +	 * @exit_dump_len: scx_exit_info.dump buffer length. If 0, the default
> +	 * value of 32768 is used.
> +	 */
> +	u32 exit_dump_len;
> +
> +	/**
> +	 * @hotplug_seq: A sequence number that may be set by the scheduler to
> +	 * detect when a hotplug event has occurred during the loading process.
> +	 * If 0, no detection occurs. Otherwise, the scheduler will fail to
> +	 * load if the sequence number does not match @scx_hotplug_seq on the
> +	 * enable path.
> +	 */
> +	u64 hotplug_seq;
> +
> +	/**
> +	 * @name: BPF scheduler's name
> +	 *
> +	 * Must be a non-zero valid BPF object name including only isalnum(),
> +	 * '_' and '.' chars. Shows up in kernel.sched_ext_ops sysctl while the
> +	 * BPF scheduler is enabled.
> +	 */
> +	char name[SCX_OPS_NAME_LEN];
> +
> +	/* internal use only, must be NULL */
> +	void *priv;
> +};
> +
> +enum scx_opi {
> +	SCX_OPI_BEGIN			= 0,
> +	SCX_OPI_NORMAL_BEGIN		= 0,
> +	SCX_OPI_NORMAL_END		= SCX_OP_IDX(cpu_online),
> +	SCX_OPI_CPU_HOTPLUG_BEGIN	= SCX_OP_IDX(cpu_online),
> +	SCX_OPI_CPU_HOTPLUG_END		= SCX_OP_IDX(init),
> +	SCX_OPI_END			= SCX_OP_IDX(init),
> +};
> +
> +/*
> + * Collection of event counters. Event types are placed in descending order.
> + */
> +struct scx_event_stats {
> +	/*
> +	 * If ops.select_cpu() returns a CPU which can't be used by the task,
> +	 * the core scheduler code silently picks a fallback CPU.
> +	 */
> +	s64		SCX_EV_SELECT_CPU_FALLBACK;
> +
> +	/*
> +	 * When dispatching to a local DSQ, the CPU may have gone offline in
> +	 * the meantime. In this case, the task is bounced to the global DSQ.
> +	 */
> +	s64		SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE;
> +
> +	/*
> +	 * If SCX_OPS_ENQ_LAST is not set, the number of times that a task
> +	 * continued to run because there were no other tasks on the CPU.
> +	 */
> +	s64		SCX_EV_DISPATCH_KEEP_LAST;
> +
> +	/*
> +	 * If SCX_OPS_ENQ_EXITING is not set, the number of times that a task
> +	 * is dispatched to a local DSQ when exiting.
> +	 */
> +	s64		SCX_EV_ENQ_SKIP_EXITING;
> +
> +	/*
> +	 * If SCX_OPS_ENQ_MIGRATION_DISABLED is not set, the number of times a
> +	 * migration disabled task skips ops.enqueue() and is dispatched to its
> +	 * local DSQ.
> +	 */
> +	s64		SCX_EV_ENQ_SKIP_MIGRATION_DISABLED;
> +
> +	/*
> +	 * Total number of times a task's time slice was refilled with the
> +	 * default value (SCX_SLICE_DFL).
> +	 */
> +	s64		SCX_EV_REFILL_SLICE_DFL;
> +
> +	/*
> +	 * The total duration of bypass modes in nanoseconds.
> +	 */
> +	s64		SCX_EV_BYPASS_DURATION;
> +
> +	/*
> +	 * The number of tasks dispatched in the bypassing mode.
> +	 */
> +	s64		SCX_EV_BYPASS_DISPATCH;
> +
> +	/*
> +	 * The number of times the bypassing mode has been activated.
> +	 */
> +	s64		SCX_EV_BYPASS_ACTIVATE;
> +};
> +
> +struct scx_sched {
> +	struct sched_ext_ops	ops;
> +	DECLARE_BITMAP(has_op, SCX_OPI_END);
> +
> +	/*
> +	 * Dispatch queues.
> +	 *
> +	 * The global DSQ (%SCX_DSQ_GLOBAL) is split per-node for scalability.
> +	 * This is to avoid live-locking in bypass mode where all tasks are
> +	 * dispatched to %SCX_DSQ_GLOBAL and all CPUs consume from it. If
> +	 * per-node split isn't sufficient, it can be further split.
> +	 */
> +	struct rhashtable	dsq_hash;
> +	struct scx_dispatch_q	**global_dsqs;
> +
> +	/*
> +	 * The event counters are in a per-CPU variable to minimize the
> +	 * accounting overhead. A system-wide view on the event counter is
> +	 * constructed when requested by scx_bpf_events().
> +	 */
> +	struct scx_event_stats __percpu *event_stats_cpu;
> +
> +	bool			warned_zero_slice;
> +
> +	atomic_t		exit_kind;
> +	struct scx_exit_info	*exit_info;
> +
> +	struct kobject		kobj;
> +
> +	struct kthread_worker	*helper;
> +	struct irq_work		error_irq_work;
> +	struct kthread_work	disable_work;
> +	struct rcu_work		rcu_work;
> +};
> +
> +enum scx_wake_flags {
> +	/* expose select WF_* flags as enums */
> +	SCX_WAKE_FORK		= WF_FORK,
> +	SCX_WAKE_TTWU		= WF_TTWU,
> +	SCX_WAKE_SYNC		= WF_SYNC,
> +};
> +
> +enum scx_enq_flags {
> +	/* expose select ENQUEUE_* flags as enums */
> +	SCX_ENQ_WAKEUP		= ENQUEUE_WAKEUP,
> +	SCX_ENQ_HEAD		= ENQUEUE_HEAD,
> +	SCX_ENQ_CPU_SELECTED	= ENQUEUE_RQ_SELECTED,
> +
> +	/* high 32bits are SCX specific */
> +
> +	/*
> +	 * Set the following to trigger preemption when calling
> +	 * scx_bpf_dsq_insert() with a local dsq as the target. The slice of the
> +	 * current task is cleared to zero and the CPU is kicked into the
> +	 * scheduling path. Implies %SCX_ENQ_HEAD.
> +	 */
> +	SCX_ENQ_PREEMPT		= 1LLU << 32,
> +
> +	/*
> +	 * The task being enqueued was previously enqueued on the current CPU's
> +	 * %SCX_DSQ_LOCAL, but was removed from it in a call to the
> +	 * scx_bpf_reenqueue_local() kfunc. If scx_bpf_reenqueue_local() was
> +	 * invoked in a ->cpu_release() callback, and the task is again
> +	 * dispatched back to %SCX_LOCAL_DSQ by this current ->enqueue(), the
> +	 * task will not be scheduled on the CPU until at least the next invocation
> +	 * of the ->cpu_acquire() callback.
> +	 */
> +	SCX_ENQ_REENQ		= 1LLU << 40,
> +
> +	/*
> +	 * The task being enqueued is the only task available for the cpu. By
> +	 * default, ext core keeps executing such tasks but when
> +	 * %SCX_OPS_ENQ_LAST is specified, they're ops.enqueue()'d with the
> +	 * %SCX_ENQ_LAST flag set.
> +	 *
> +	 * The BPF scheduler is responsible for triggering a follow-up
> +	 * scheduling event. Otherwise, Execution may stall.
> +	 */
> +	SCX_ENQ_LAST		= 1LLU << 41,
> +
> +	/* high 8 bits are internal */
> +	__SCX_ENQ_INTERNAL_MASK	= 0xffLLU << 56,
> +
> +	SCX_ENQ_CLEAR_OPSS	= 1LLU << 56,
> +	SCX_ENQ_DSQ_PRIQ	= 1LLU << 57,
> +};
> +
> +enum scx_deq_flags {
> +	/* expose select DEQUEUE_* flags as enums */
> +	SCX_DEQ_SLEEP		= DEQUEUE_SLEEP,
> +
> +	/* high 32bits are SCX specific */
> +
> +	/*
> +	 * The generic core-sched layer decided to execute the task even though
> +	 * it hasn't been dispatched yet. Dequeue from the BPF side.
> +	 */
> +	SCX_DEQ_CORE_SCHED_EXEC	= 1LLU << 32,
> +};
> +
> +enum scx_pick_idle_cpu_flags {
> +	SCX_PICK_IDLE_CORE	= 1LLU << 0,	/* pick a CPU whose SMT siblings are also idle */
> +	SCX_PICK_IDLE_IN_NODE	= 1LLU << 1,	/* pick a CPU in the same target NUMA node */
> +};
> +
> +enum scx_kick_flags {
> +	/*
> +	 * Kick the target CPU if idle. Guarantees that the target CPU goes
> +	 * through at least one full scheduling cycle before going idle. If the
> +	 * target CPU can be determined to be currently not idle and going to go
> +	 * through a scheduling cycle before going idle, noop.
> +	 */
> +	SCX_KICK_IDLE		= 1LLU << 0,
> +
> +	/*
> +	 * Preempt the current task and execute the dispatch path. If the
> +	 * current task of the target CPU is an SCX task, its ->scx.slice is
> +	 * cleared to zero before the scheduling path is invoked so that the
> +	 * task expires and the dispatch path is invoked.
> +	 */
> +	SCX_KICK_PREEMPT	= 1LLU << 1,
> +
> +	/*
> +	 * Wait for the CPU to be rescheduled. The scx_bpf_kick_cpu() call will
> +	 * return after the target CPU finishes picking the next task.
> +	 */
> +	SCX_KICK_WAIT		= 1LLU << 2,
> +};
> +
> +enum scx_tg_flags {
> +	SCX_TG_ONLINE		= 1U << 0,
> +	SCX_TG_INITED		= 1U << 1,
> +};
> +
> +enum scx_enable_state {
> +	SCX_ENABLING,
> +	SCX_ENABLED,
> +	SCX_DISABLING,
> +	SCX_DISABLED,
> +};
> +
> +static const char *scx_enable_state_str[] = {
> +	[SCX_ENABLING]		= "enabling",
> +	[SCX_ENABLED]		= "enabled",
> +	[SCX_DISABLING]		= "disabling",
> +	[SCX_DISABLED]		= "disabled",
> +};
> +
> +/*
> + * sched_ext_entity->ops_state
> + *
> + * Used to track the task ownership between the SCX core and the BPF scheduler.
> + * State transitions look as follows:
> + *
> + * NONE -> QUEUEING -> QUEUED -> DISPATCHING
> + *   ^              |                 |
> + *   |              v                 v
> + *   \-------------------------------/
> + *
> + * QUEUEING and DISPATCHING states can be waited upon. See wait_ops_state() call
> + * sites for explanations on the conditions being waited upon and why they are
> + * safe. Transitions out of them into NONE or QUEUED must store_release and the
> + * waiters should load_acquire.
> + *
> + * Tracking scx_ops_state enables sched_ext core to reliably determine whether
> + * any given task can be dispatched by the BPF scheduler at all times and thus
> + * relaxes the requirements on the BPF scheduler. This allows the BPF scheduler
> + * to try to dispatch any task anytime regardless of its state as the SCX core
> + * can safely reject invalid dispatches.
> + */
> +enum scx_ops_state {
> +	SCX_OPSS_NONE,		/* owned by the SCX core */
> +	SCX_OPSS_QUEUEING,	/* in transit to the BPF scheduler */
> +	SCX_OPSS_QUEUED,	/* owned by the BPF scheduler */
> +	SCX_OPSS_DISPATCHING,	/* in transit back to the SCX core */
> +
> +	/*
> +	 * QSEQ brands each QUEUED instance so that, when dispatch races
> +	 * dequeue/requeue, the dispatcher can tell whether it still has a claim
> +	 * on the task being dispatched.
> +	 *
> +	 * As some 32bit archs can't do 64bit store_release/load_acquire,
> +	 * p->scx.ops_state is atomic_long_t which leaves 30 bits for QSEQ on
> +	 * 32bit machines. The dispatch race window QSEQ protects is very narrow
> +	 * and runs with IRQ disabled. 30 bits should be sufficient.
> +	 */
> +	SCX_OPSS_QSEQ_SHIFT	= 2,
> +};
> +
> +/* Use macros to ensure that the type is unsigned long for the masks */
> +#define SCX_OPSS_STATE_MASK	((1LU << SCX_OPSS_QSEQ_SHIFT) - 1)
> +#define SCX_OPSS_QSEQ_MASK	(~SCX_OPSS_STATE_MASK)
> +
> +DECLARE_PER_CPU(struct rq *, scx_locked_rq_state);
> +
> +/*
> + * Return the rq currently locked from an scx callback, or NULL if no rq is
> + * locked.
> + */
> +static inline struct rq *scx_locked_rq(void)
> +{
> +	return __this_cpu_read(scx_locked_rq_state);
> +}
> +
> +static inline bool scx_kf_allowed_if_unlocked(void)
> +{
> +	return !current->scx.kf_mask;
> +}
> +
> +static inline bool scx_rq_bypassing(struct rq *rq)
> +{
> +	return unlikely(rq->scx.flags & SCX_RQ_BYPASSING);
> +}
> -- 
> 2.51.0
> 

Re: [PATCH 3/4] sched_ext: Move internal type and accessor definitions to ext_internal.h

[Tejun Heo]

Hello,

On Wed, Sep 03, 2025 at 12:32:29PM +0200, Andrea Righi wrote:
> On Tue, Sep 02, 2025 at 01:48:05PM -1000, Tejun Heo wrote:
> > There currently isn't a place to place SCX-internal types and accessors to
> > be shared between ext.c and ext_idle.c. Create kernel/sched/ext_internal.h
> > and move internal type and accessor definitions there. This trims ext.c a
> > bit and makes future additions easier. Pure code reorganization. No
> > functional changes.
> 
> Having sched_ext_ops and scx_*_flags defined in ext_internal.h feels a
> bit counterintuitive, sched_ext_ops also includes the documentation for all
> the scx callbacks. How about moving these to ext.h and everything else in
> ext_internal.h?

Hmm... so, _internal headers are for things which aren't interesting to
other subsystems in the kernel. ie. internal to this particular subsystem,
which is the case here. I understand that _internal may be counter-intuitive
if the reader isn't working in the kernel tree, but am not sure that's a
primary concern in naming source files.

Thanks.

-- 
tejun

Re: [PATCH 3/4] sched_ext: Move internal type and accessor definitions to ext_internal.h

[Andrea Righi]

On Wed, Sep 03, 2025 at 07:00:56AM -1000, Tejun Heo wrote:
> Hello,
> 
> On Wed, Sep 03, 2025 at 12:32:29PM +0200, Andrea Righi wrote:
> > On Tue, Sep 02, 2025 at 01:48:05PM -1000, Tejun Heo wrote:
> > > There currently isn't a place to place SCX-internal types and accessors to
> > > be shared between ext.c and ext_idle.c. Create kernel/sched/ext_internal.h
> > > and move internal type and accessor definitions there. This trims ext.c a
> > > bit and makes future additions easier. Pure code reorganization. No
> > > functional changes.
> > 
> > Having sched_ext_ops and scx_*_flags defined in ext_internal.h feels a
> > bit counterintuitive, sched_ext_ops also includes the documentation for all
> > the scx callbacks. How about moving these to ext.h and everything else in
> > ext_internal.h?
> 
> Hmm... so, _internal headers are for things which aren't interesting to
> other subsystems in the kernel. ie. internal to this particular subsystem,
> which is the case here. I understand that _internal may be counter-intuitive
> if the reader isn't working in the kernel tree, but am not sure that's a
> primary concern in naming source files.

Yeah, that's probably fine. As for the documentation, it's easy to find it
anyway, so I think it's not an issue.

Everything else looks good to me, so for the whole patchset:

Acked-by: Andrea Righi <arighi@nvidia.com>

Thanks,
-Andrea

[PATCH 4/4] sched_ext: Put event_stats_cpu in struct scx_sched_pcpu

[Tejun Heo]

scx_sched.event_stats_cpu is the percpu counters that are used to track
stats. Introduce struct scx_sched_pcpu and move the counters inside. This
will ease adding more per-cpu fields. No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 kernel/sched/ext.c          | 18 +++++++++---------
 kernel/sched/ext_internal.h | 17 ++++++++++-------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 7e15e852370c..701ca239ad00 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -635,7 +635,7 @@ static struct task_struct *scx_task_iter_next_locked(struct scx_task_iter *iter)
  * This can be used when preemption is not disabled.
  */
 #define scx_add_event(sch, name, cnt) do {					\
-	this_cpu_add((sch)->event_stats_cpu->name, (cnt));			\
+	this_cpu_add((sch)->pcpu->event_stats.name, (cnt));			\
 	trace_sched_ext_event(#name, (cnt));					\
 } while(0)
 
@@ -648,7 +648,7 @@ static struct task_struct *scx_task_iter_next_locked(struct scx_task_iter *iter)
  * This should be used only when preemption is disabled.
  */
 #define __scx_add_event(sch, name, cnt) do {					\
-	__this_cpu_add((sch)->event_stats_cpu->name, (cnt));			\
+	__this_cpu_add((sch)->pcpu->event_stats.name, (cnt));			\
 	trace_sched_ext_event(#name, cnt);					\
 } while(0)
 
@@ -3543,7 +3543,7 @@ static void scx_sched_free_rcu_work(struct work_struct *work)
 	int node;
 
 	kthread_stop(sch->helper->task);
-	free_percpu(sch->event_stats_cpu);
+	free_percpu(sch->pcpu);
 
 	for_each_node_state(node, N_POSSIBLE)
 		kfree(sch->global_dsqs[node]);
@@ -4444,13 +4444,13 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops)
 		sch->global_dsqs[node] = dsq;
 	}
 
-	sch->event_stats_cpu = alloc_percpu(struct scx_event_stats);
-	if (!sch->event_stats_cpu)
+	sch->pcpu = alloc_percpu(struct scx_sched_pcpu);
+	if (!sch->pcpu)
 		goto err_free_gdsqs;
 
 	sch->helper = kthread_run_worker(0, "sched_ext_helper");
 	if (!sch->helper)
-		goto err_free_event_stats;
+		goto err_free_pcpu;
 	sched_set_fifo(sch->helper->task);
 
 	atomic_set(&sch->exit_kind, SCX_EXIT_NONE);
@@ -4468,8 +4468,8 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops)
 
 err_stop_helper:
 	kthread_stop(sch->helper->task);
-err_free_event_stats:
-	free_percpu(sch->event_stats_cpu);
+err_free_pcpu:
+	free_percpu(sch->pcpu);
 err_free_gdsqs:
 	for_each_node_state(node, N_POSSIBLE)
 		kfree(sch->global_dsqs[node]);
@@ -6493,7 +6493,7 @@ static void scx_read_events(struct scx_sched *sch, struct scx_event_stats *event
 	/* Aggregate per-CPU event counters into @events. */
 	memset(events, 0, sizeof(*events));
 	for_each_possible_cpu(cpu) {
-		e_cpu = per_cpu_ptr(sch->event_stats_cpu, cpu);
+		e_cpu = &per_cpu_ptr(sch->pcpu, cpu)->event_stats;
 		scx_agg_event(events, e_cpu, SCX_EV_SELECT_CPU_FALLBACK);
 		scx_agg_event(events, e_cpu, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE);
 		scx_agg_event(events, e_cpu, SCX_EV_DISPATCH_KEEP_LAST);
diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
index 76690ede8700..af4c054fb6f8 100644
--- a/kernel/sched/ext_internal.h
+++ b/kernel/sched/ext_internal.h
@@ -846,6 +846,15 @@ struct scx_event_stats {
 	s64		SCX_EV_BYPASS_ACTIVATE;
 };
 
+struct scx_sched_pcpu {
+	/*
+	 * The event counters are in a per-CPU variable to minimize the
+	 * accounting overhead. A system-wide view on the event counter is
+	 * constructed when requested by scx_bpf_events().
+	 */
+	struct scx_event_stats	event_stats;
+};
+
 struct scx_sched {
 	struct sched_ext_ops	ops;
 	DECLARE_BITMAP(has_op, SCX_OPI_END);
@@ -860,13 +869,7 @@ struct scx_sched {
 	 */
 	struct rhashtable	dsq_hash;
 	struct scx_dispatch_q	**global_dsqs;
-
-	/*
-	 * The event counters are in a per-CPU variable to minimize the
-	 * accounting overhead. A system-wide view on the event counter is
-	 * constructed when requested by scx_bpf_events().
-	 */
-	struct scx_event_stats __percpu *event_stats_cpu;
+	struct scx_sched_pcpu __percpu *pcpu;
 
 	bool			warned_zero_slice;
 
-- 
2.51.0

Re: [PATCHSET sched_ext/for-6.18] sched_ext: Misc changes

[Tejun Heo]

On Tue, Sep 02, 2025 at 01:48:02PM -1000, Tejun Heo wrote:
> A collection of four misc patches.
> 
> - Make scx_task_iter a bit easier to use.
> 
> - Keep bypass on between enable failure and disable.
> 
> - Move types and accessors into ext_internal.h.
> 
> - Wrap event percpu allocation in a struct to ease adding more percpu
>   fields.
> 
>  0001-sched_ext-Make-explicit-scx_task_iter_relock-calls-u.patch
>  0002-sched_ext-Keep-bypass-on-between-enable-failure-and-.patch
>  0003-sched_ext-Move-internal-type-and-accessor-definition.patch
>  0004-sched_ext-Put-event_stats_cpu-in-struct-scx_sched_pc.patch

Applied to sched_ext/for-6.18.

Thanks.

-- 
tejun