sched, sched_ext: Move some declarations from kernel/sched/ext.h to sched.h

While sched_ext was out of tree, everything sched_ext specific which can be
put in kernel/sched/ext.h was put there to ease forward porting. However,
kernel/sched/sched.h is the better location for some of them. Relocate.

- struct sched_enq_and_set_ctx, sched_deq_and_put_task() and
  sched_enq_and_set_task().

- scx_enabled() and scx_switched_all().

- for_active_class_range() and for_each_active_class(). sched_class
  declarations are moved above the class iterators for this.

No functional changes intended.
Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Vernet <void@manifault.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

kernel/sched/ext.h

@@ -8,24 +8,6 @@
  */
 #ifdef CONFIG_SCHED_CLASS_EXT
 
-struct sched_enq_and_set_ctx {
-	struct task_struct	*p;
-	int			queue_flags;
-	bool			queued;
-	bool			running;
-};
-
-void sched_deq_and_put_task(struct task_struct *p, int queue_flags,
-			    struct sched_enq_and_set_ctx *ctx);
-void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx);
-
-extern const struct sched_class ext_sched_class;
-
-DECLARE_STATIC_KEY_FALSE(__scx_ops_enabled);
-DECLARE_STATIC_KEY_FALSE(__scx_switched_all);
-#define scx_enabled()		static_branch_unlikely(&__scx_ops_enabled)
-#define scx_switched_all()	static_branch_unlikely(&__scx_switched_all)
-
 void scx_tick(struct rq *rq);
 void init_scx_entity(struct sched_ext_entity *scx);
 void scx_pre_fork(struct task_struct *p);
@@ -52,22 +34,6 @@ static inline bool task_on_scx(const struct task_struct *p)
 	return scx_enabled() && p->sched_class == &ext_sched_class;
 }
 
-static inline const struct sched_class *next_active_class(const struct sched_class *class)
-{
-	class++;
-	if (scx_switched_all() && class == &fair_sched_class)
-		class++;
-	if (!scx_enabled() && class == &ext_sched_class)
-		class++;
-	return class;
-}
-
-#define for_active_class_range(class, _from, _to)				\
-	for (class = (_from); class != (_to); class = next_active_class(class))
-
-#define for_each_active_class(class)						\
-	for_active_class_range(class, __sched_class_highest, __sched_class_lowest)
-
 #ifdef CONFIG_SCHED_CORE
 bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 		   bool in_fi);
@@ -75,9 +41,6 @@ bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
 
 #else	/* CONFIG_SCHED_CLASS_EXT */
 
-#define scx_enabled()		false
-#define scx_switched_all()	false
-
 static inline void scx_tick(struct rq *rq) {}
 static inline void scx_pre_fork(struct task_struct *p) {}
 static inline int scx_fork(struct task_struct *p) { return 0; }
@@ -91,8 +54,6 @@ static inline int scx_check_setscheduler(struct task_struct *p, int policy) { re
 static inline bool task_on_scx(const struct task_struct *p) { return false; }
 static inline void init_sched_ext_class(void) {}
 
-#define for_each_active_class		for_each_class
-
 #endif	/* CONFIG_SCHED_CLASS_EXT */
 
 #if defined(CONFIG_SCHED_CLASS_EXT) && defined(CONFIG_SMP)

kernel/sched/sched.h

@@ -2438,19 +2438,54 @@ const struct sched_class name##_sched_class \
 extern struct sched_class __sched_class_highest[];
 extern struct sched_class __sched_class_lowest[];
 
+extern const struct sched_class stop_sched_class;
+extern const struct sched_class dl_sched_class;
+extern const struct sched_class rt_sched_class;
+extern const struct sched_class fair_sched_class;
+extern const struct sched_class idle_sched_class;
+
+#ifdef CONFIG_SCHED_CLASS_EXT
+extern const struct sched_class ext_sched_class;
+
+DECLARE_STATIC_KEY_FALSE(__scx_ops_enabled);	/* SCX BPF scheduler loaded */
+DECLARE_STATIC_KEY_FALSE(__scx_switched_all);	/* all fair class tasks on SCX */
+
+#define scx_enabled()		static_branch_unlikely(&__scx_ops_enabled)
+#define scx_switched_all()	static_branch_unlikely(&__scx_switched_all)
+#else /* !CONFIG_SCHED_CLASS_EXT */
+#define scx_enabled()		false
+#define scx_switched_all()	false
+#endif /* !CONFIG_SCHED_CLASS_EXT */
+
+/*
+ * Iterate only active classes. SCX can take over all fair tasks or be
+ * completely disabled. If the former, skip fair. If the latter, skip SCX.
+ */
+static inline const struct sched_class *next_active_class(const struct sched_class *class)
+{
+	class++;
+#ifdef CONFIG_SCHED_CLASS_EXT
+	if (scx_switched_all() && class == &fair_sched_class)
+		class++;
+	if (!scx_enabled() && class == &ext_sched_class)
+		class++;
+#endif
+	return class;
+}
+
 #define for_class_range(class, _from, _to) \
 	for (class = (_from); class < (_to); class++)
 
 #define for_each_class(class) \
 	for_class_range(class, __sched_class_highest, __sched_class_lowest)
 
-#define sched_class_above(_a, _b)	((_a) < (_b))
+#define for_active_class_range(class, _from, _to)				\
+	for (class = (_from); class != (_to); class = next_active_class(class))
 
-extern const struct sched_class stop_sched_class;
-extern const struct sched_class dl_sched_class;
-extern const struct sched_class rt_sched_class;
-extern const struct sched_class fair_sched_class;
-extern const struct sched_class idle_sched_class;
+#define for_each_active_class(class)						\
+	for_active_class_range(class, __sched_class_highest, __sched_class_lowest)
+
+#define sched_class_above(_a, _b)	((_a) < (_b))
 
 static inline bool sched_stop_runnable(struct rq *rq)
 {
@@ -3698,6 +3733,24 @@ static inline void balance_callbacks(struct rq *rq, struct balance_callback *hea
 
 #endif
 
+#ifdef CONFIG_SCHED_CLASS_EXT
+/*
+ * Used by SCX in the enable/disable paths to move tasks between sched_classes
+ * and establish invariants.
+ */
+struct sched_enq_and_set_ctx {
+	struct task_struct	*p;
+	int			queue_flags;
+	bool			queued;
+	bool			running;
+};
+
+void sched_deq_and_put_task(struct task_struct *p, int queue_flags,
+			    struct sched_enq_and_set_ctx *ctx);
+void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx);
+
+#endif /* CONFIG_SCHED_CLASS_EXT */
+
 #include "ext.h"
 
 #endif /* _KERNEL_SCHED_SCHED_H */