sched_ext: Rename balance-era identifiers to dispatch terms

sched_class->balance() is gone from sched_ext and what balance_one() does is
run dispatch to produce something pickable. Update the balance-era names to
dispatch terms:

- balance_one() -> dispatch_one()
- SCX_RQ_IN_BALANCE -> SCX_RQ_IN_DISPATCH

No BPF scheduler reads the flag. The enum autogen headers gain the new name
with the old entry retained like other removed enumerators, zero-filling at
load time. No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/sched/ext/ext.c

@@ -377,9 +377,9 @@ static bool rq_is_open(struct rq *rq, u64 enq_flags)
 	 * If we're in the dispatch path holding rq lock, $curr may or may not
 	 * be ready depending on whether the on-going dispatch decides to extend
 	 * $curr's slice. We say yes here and resolve it at the end of dispatch.
-	 * See balance_one().
+	 * See dispatch_one().
 	 */
-	if (rq->scx.flags & SCX_RQ_IN_BALANCE)
+	if (rq->scx.flags & SCX_RQ_IN_DISPATCH)
 		return true;
 
 	/*
@@ -1019,7 +1019,7 @@ static void schedule_deferred(struct rq *rq)
 	/*
 	 * This is the fallback when schedule_deferred_locked() can't use
 	 * the cheaper balance callback or wakeup hook paths (the target
-	 * CPU is not in balance or wakeup). Currently, this is primarily
+	 * CPU is not in dispatch or wakeup). Currently, this is primarily
 	 * hit by reenqueue operations targeting a remote CPU.
 	 *
 	 * Queue on the target CPU. The deferred work can run from any CPU
@@ -1055,25 +1055,25 @@ static void schedule_deferred_locked(struct rq *rq)
 		return;
 
 	/*
-	 * If in balance, the balance callbacks will be called before rq lock is
-	 * released. Schedule one.
+	 * If in dispatch, the balance callbacks will be called before rq lock
+	 * is released. Schedule one.
 	 *
 	 *
 	 * We can't directly insert the callback into the
 	 * rq's list: The call can drop its lock and make the pending balance
 	 * callback visible to unrelated code paths that call rq_pin_lock().
 	 *
-	 * Just let balance_one() know that it must do it itself.
+	 * Just let dispatch_one() know that it must do it itself.
 	 */
-	if (rq->scx.flags & SCX_RQ_IN_BALANCE) {
+	if (rq->scx.flags & SCX_RQ_IN_DISPATCH) {
 		rq->scx.flags |= SCX_RQ_BAL_CB_PENDING;
 		return;
 	}
 
 	/*
 	 * No scheduler hooks available. Use the generic irq_work path. The
-	 * above WAKEUP and BALANCE paths should cover most of the cases and the
-	 * time to IRQ re-enable shouldn't be long.
+	 * above WAKEUP and DISPATCH paths should cover most of the cases and
+	 * the time to IRQ re-enable shouldn't be long.
 	 */
 	schedule_deferred(rq);
 }
@@ -1616,14 +1616,14 @@ static void rq_owned_post_enq(struct scx_sched *sch, struct rq *rq,
 		wakeup_preempt(rq, p, 0);
 
 	/*
-	 * If @rq is in balance, the CPU is already vacant and looking for the
+	 * If @rq is in dispatch, the CPU is already vacant and looking for the
 	 * next task to run. No need to preempt or trigger resched after moving
 	 * @p into its local DSQ.
 	 * Note that the wakeup_preempt() above may have already triggered
 	 * a resched if @rq->next_class was idle. It's harmless, since
 	 * need_resched is cleared immediately after task pick.
 	 */
-	if (rq->scx.flags & SCX_RQ_IN_BALANCE)
+	if (rq->scx.flags & SCX_RQ_IN_DISPATCH)
 		return;
 
 	if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr &&
@@ -2348,7 +2348,7 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int core_deq_
 	 *
 	 * @p may go through multiple stopping <-> running transitions between
 	 * here and put_prev_task_scx() if task attribute changes occur while
-	 * balance_one() leaves @rq unlocked. However, they don't contain any
+	 * dispatch_one() leaves @rq unlocked. However, they don't contain any
 	 * information meaningful to the BPF scheduler and can be suppressed by
 	 * skipping the callbacks if the task is !QUEUED.
 	 */
@@ -2976,14 +2976,14 @@ static inline void maybe_queue_balance_callback(struct rq *rq)
 	rq->scx.flags &= ~SCX_RQ_BAL_CB_PENDING;
 }
 
-static enum scx_dsp_verdict balance_one(struct rq *rq, struct task_struct *prev)
+static enum scx_dsp_verdict dispatch_one(struct rq *rq, struct task_struct *prev)
 {
 	struct scx_sched *sch = scx_root_protected_live();
 	enum scx_dsp_verdict verdict;
 	s32 cpu = cpu_of(rq);
 
 	lockdep_assert_rq_held(rq);
-	rq->scx.flags |= SCX_RQ_IN_BALANCE;
+	rq->scx.flags |= SCX_RQ_IN_DISPATCH;
 
 	scx_process_sync_ecaps(rq, prev);
 
@@ -3041,7 +3041,7 @@ static enum scx_dsp_verdict balance_one(struct rq *rq, struct task_struct *prev)
 		verdict = SCX_DSP_PREV;
 		goto has_tasks;
 	}
-	rq->scx.flags &= ~SCX_RQ_IN_BALANCE;
+	rq->scx.flags &= ~SCX_RQ_IN_DISPATCH;
 	return SCX_DSP_NONE;
 
 has_tasks:
@@ -3058,7 +3058,7 @@ static enum scx_dsp_verdict balance_one(struct rq *rq, struct task_struct *prev)
 	if (unlikely(rq->scx.local_dsq.nr > 1 && rq->scx.nr_immed))
 		scx_schedule_reenq_local(rq, 0);
 
-	rq->scx.flags &= ~SCX_RQ_IN_BALANCE;
+	rq->scx.flags &= ~SCX_RQ_IN_DISPATCH;
 	return verdict;
 }
 
@@ -3159,7 +3159,7 @@ static void switch_class(struct rq *rq, struct task_struct *next)
 	 * preempted, and it regaining control of the CPU.
 	 *
 	 * ->cpu_release() complements ->cpu_acquire(), which is emitted the
-	 *  next time that balance_one() is invoked.
+	 *  next time that dispatch_one() is invoked.
 	 */
 	if (!rq->scx.cpu_released) {
 		if (sch->ops.cpu_release) {
@@ -3340,7 +3340,7 @@ static enum scx_dsp_verdict dispatch_pick(struct rq *rq, struct rq_flags *rf,
 	enum scx_dsp_verdict verdict;
 
 	rq_unpin_lock(rq, rf);
-	verdict = balance_one(rq, prev);
+	verdict = dispatch_one(rq, prev);
 	rq_repin_lock(rq, rf);
 	maybe_queue_balance_callback(rq);
 
@@ -3373,12 +3373,12 @@ static enum scx_dsp_verdict dispatch_core_pick(struct rq *rq, struct rq_flags *r
 	u32 seq = rq->scx.lock_drop_seq;
 
 	/* another dispatch is in flight on @rq, let that handle it */
-	if (rq->scx.flags & SCX_RQ_IN_BALANCE)
+	if (rq->scx.flags & SCX_RQ_IN_DISPATCH)
 		return SCX_DSP_NONE;
 
 	rq_unpin_lock(rq, rf);
 
-	verdict = balance_one(rq, prev);
+	verdict = dispatch_one(rq, prev);
 
 	if (cpu_of(rq) == smp_processor_id()) {
 		maybe_queue_balance_callback(rq);
@@ -3401,7 +3401,7 @@ static enum scx_dsp_verdict dispatch_core_pick(struct rq *rq, struct rq_flags *r
 
 	rq_repin_lock(rq, rf);
 
-	/* if balance_one() released the rq lock, restart the selection */
+	/* if dispatch_one() released the rq lock, restart the selection */
 	if (rq->scx.lock_drop_seq != seq)
 		return SCX_DSP_RETRY;
 
@@ -3437,7 +3437,7 @@ do_pick_task_scx(struct rq *rq, struct rq_flags *rf, bool force_scx)
 
 	/*
 	 * If any higher-priority sched class enqueued a runnable task on this
-	 * rq during balance_one(), abort and return RETRY_TASK, so that the
+	 * rq during dispatch_one(), abort and return RETRY_TASK, so that the
 	 * scheduler loop can restart.
 	 *
 	 * If @force_scx is true, always try to pick a SCHED_EXT task,
@@ -6077,7 +6077,7 @@ static void unbypass_renotify_idle(struct rq *rq, struct scx_sched *pos,
  *
  * - ops.dispatch() is ignored.
  *
- * - balance_one() does not report %SCX_DSP_PREV on non-zero slice as slice
+ * - dispatch_one() does not report %SCX_DSP_PREV on non-zero slice as slice
  *   can't be trusted. Whenever a tick triggers, the running task is rotated to
  *   the tail of the queue with core_sched_at touched.
  *
@@ -8460,13 +8460,13 @@ static bool can_skip_idle_kick(struct rq *rq)
 	 * We can skip idle kicking if @rq is going to go through at least one
 	 * full SCX scheduling cycle before going idle. Just checking whether
 	 * curr is not idle is insufficient because we could be racing
-	 * balance_one() trying to pull the next task from a remote rq, which
+	 * dispatch_one() trying to pull the next task from a remote rq, which
 	 * may fail, and @rq may become idle afterwards.
 	 *
 	 * The race window is small and we don't and can't guarantee that @rq is
 	 * only kicked while idle anyway. Skip only when sure.
 	 */
-	return !is_idle_task(rq->curr) && !(rq->scx.flags & SCX_RQ_IN_BALANCE);
+	return !is_idle_task(rq->curr) && !(rq->scx.flags & SCX_RQ_IN_DISPATCH);
 }
 
 static bool kick_one_cpu(s32 cpu, struct scx_sched_pcpu *pcpu, struct rq *this_rq,
@@ -9199,7 +9199,7 @@ __bpf_kfunc bool scx_bpf_dsq_move_to_local___v2(u64 dsq_id, u64 enq_flags,
 		/*
 		 * A successfully consumed task can be dequeued before it starts
 		 * running while the CPU is trying to migrate other dispatched
-		 * tasks. Bump nr_tasks to tell balance_one() to retry on empty
+		 * tasks. Bump nr_tasks to tell dispatch_one() to retry on empty
 		 * local DSQ.
 		 */
 		dspc->nr_tasks++;

kernel/sched/ext/inlines.h

@@ -112,7 +112,7 @@ scx_dispatch_sched(struct scx_sched *sch, struct rq *rq,
 		 * ops.dispatch() can trap us in this loop by repeatedly
 		 * dispatching ineligible tasks. Break out once in a while to
 		 * allow the watchdog to run. As IRQ can't be enabled in
-		 * balance(), we want to complete this scheduling cycle and then
+		 * dispatch, we want to complete this scheduling cycle and then
 		 * start a new one. IOW, we want to call resched_curr() on the
 		 * next, most likely idle, task, not the current one. Use
 		 * __scx_bpf_kick_cpu() for deferred kicking.

kernel/sched/ext/sub.c

@@ -918,7 +918,7 @@ static u64 calc_effective_caps(struct scx_pshard *ps, s32 cid)
  * @cid: cid to update
  *
  * Queue an ecaps update for @sch's @cid and kick the cpu so that it syncs in
- * balance_one().
+ * dispatch_one().
  */
 static void queue_sync_ecaps(struct scx_sched *sch, s32 cid)
 {
@@ -953,7 +953,7 @@ static void discard_queued_syncs(struct rq *rq)
 /**
  * scx_process_sync_ecaps - Sync this cpu's ecaps to pshard->caps[]
  * @rq: the cid's cpu rq
- * @prev: @rq's previous task from the in-progress balance
+ * @prev: @rq's previous task from the in-progress dispatch
  *
  * pshard->caps[] is the target configuration. pcpu->ecaps is the effective
  * transposed copy owned by the cid's cpu and written only here under @rq's
@@ -1069,7 +1069,7 @@ void scx_process_sync_ecaps(struct rq *rq, struct task_struct *prev)
  * sync when bypass lifts, so without a replay a cid that never changes again
  * would never be notified. The attach-time initial grants are the acute case
  * as they are consumed during the enable bypass window. Re-queue a sync for
- * any undelivered delta so the next balance delivers it.
+ * any undelivered delta so the next dispatch delivers it.
  */
 void scx_unbypass_replay_ecaps(struct rq *rq, struct scx_sched *sch)
 {
@@ -2248,7 +2248,7 @@ __bpf_kfunc bool scx_bpf_sub_dispatch(u64 cgroup_id, const struct bpf_prog_aux *
 	/*
 	 * Skip a child that does not effectively hold the base cap on this cpu:
 	 * its inserts would only be rejected. ecaps are synced at the top of
-	 * balance_one() before dispatch, so this reflects the in-effect state.
+	 * dispatch_one() before dispatch, so this reflects the in-effect state.
 	 */
 	if (scx_missing_caps(child, cpu_of(rq), SCX_CAP_BASE))
 		return false;

kernel/sched/sched.h

@@ -790,7 +790,7 @@ enum scx_rq_flags {
 	SCX_RQ_ROOT_IDLE_RENOTIFY	= 1 << 8, /* the root is owed update_idle() */
 
 	SCX_RQ_IN_WAKEUP	= 1 << 16,
-	SCX_RQ_IN_BALANCE	= 1 << 17,
+	SCX_RQ_IN_DISPATCH	= 1 << 17,
 };
 
 /* per-rq rescue execution state, see scx_rescue_timerfn() */

tools/sched_ext/include/scx/enum_defs.autogen.h

@@ -189,6 +189,7 @@
 #define HAVE_SCX_RQ_ROOT_IDLE_RENOTIFY
 #define HAVE_SCX_RQ_IN_WAKEUP
 #define HAVE_SCX_RQ_IN_BALANCE
+#define HAVE_SCX_RQ_IN_DISPATCH
 #define HAVE_SCX_SCHED_PCPU_BYPASSING
 #define HAVE_SCX_SLICE_OOB_DUR_BITS
 #define HAVE_SCX_SLICE_OOB_ID_BITS

tools/sched_ext/include/scx/enums.autogen.bpf.h

@@ -34,6 +34,9 @@ const volatile u64 __SCX_RQ_IN_WAKEUP __weak;
 const volatile u64 __SCX_RQ_IN_BALANCE __weak;
 #define SCX_RQ_IN_BALANCE __SCX_RQ_IN_BALANCE
 
+const volatile u64 __SCX_RQ_IN_DISPATCH __weak;
+#define SCX_RQ_IN_DISPATCH __SCX_RQ_IN_DISPATCH
+
 const volatile u64 __SCX_DSQ_FLAG_BUILTIN __weak;
 #define SCX_DSQ_FLAG_BUILTIN __SCX_DSQ_FLAG_BUILTIN
 

tools/sched_ext/include/scx/enums.autogen.h

@@ -15,6 +15,7 @@
 	SCX_ENUM_SET(skel, scx_rq_flags, SCX_RQ_CLK_VALID); \
 	SCX_ENUM_SET(skel, scx_rq_flags, SCX_RQ_IN_WAKEUP); \
 	SCX_ENUM_SET(skel, scx_rq_flags, SCX_RQ_IN_BALANCE); \
+	SCX_ENUM_SET(skel, scx_rq_flags, SCX_RQ_IN_DISPATCH); \
 	SCX_ENUM_SET(skel, scx_dsq_id_flags, SCX_DSQ_FLAG_BUILTIN); \
 	SCX_ENUM_SET(skel, scx_dsq_id_flags, SCX_DSQ_FLAG_LOCAL_ON); \
 	SCX_ENUM_SET(skel, scx_dsq_id_flags, SCX_DSQ_INVALID); \