scx: Remove enum rq_onoff_reason enum

The existing hotplug code is a bit brittle in that the sched_class->{online,
offline} callbacks can be invoked both from hotplug context, or from domain
rebuild context. A callback is only invoked in one of the two contexts, with
the context that runs the callback setting rq->online accordingly to avoid
doing the callback more times than necessary. Unfortuntaly, this causes commit
2125c00 ("cgroup/cpuset: Make cpuset hotplug processing synchronous") to
break hotplug for us because it makes the topology rq->online event happen
before the cpu hotplug rq->online event; thus preventing us from invoking the
cpu online callback in the scheduler.

This integration is fragile and hacky, so we'll instead call directly into
ext.c on the hotplug path. This will be added in a subsequent commit.

Signed-off-by: David Vernet <void@manifault.com>

kernel/sched/core.c

@@ -9670,7 +9670,7 @@ static inline void balance_hotplug_wait(void)
 
 #endif /* CONFIG_HOTPLUG_CPU */
 
-void set_rq_online(struct rq *rq, enum rq_onoff_reason reason)
+void set_rq_online(struct rq *rq)
 {
 	if (!rq->online) {
 		const struct sched_class *class;
@@ -9680,20 +9680,20 @@ void set_rq_online(struct rq *rq, enum rq_onoff_reason reason)
 
 		for_each_class(class) {
 			if (class->rq_online)
-				class->rq_online(rq, reason);
+				class->rq_online(rq);
 		}
 	}
 }
 
-void set_rq_offline(struct rq *rq, enum rq_onoff_reason reason)
+void set_rq_offline(struct rq *rq)
 {
 	if (rq->online) {
 		const struct sched_class *class;
 
 		update_rq_clock(rq);
 		for_each_class(class) {
 			if (class->rq_offline)
-				class->rq_offline(rq, reason);
+				class->rq_offline(rq);
 		}
 
 		cpumask_clear_cpu(rq->cpu, rq->rd->online);
@@ -9789,7 +9789,7 @@ int sched_cpu_activate(unsigned int cpu)
 	rq_lock_irqsave(rq, &rf);
 	if (rq->rd) {
 		BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
-		set_rq_online(rq, RQ_ONOFF_HOTPLUG);
+		set_rq_online(rq);
 	}
 	rq_unlock_irqrestore(rq, &rf);
 
@@ -9833,7 +9833,7 @@ int sched_cpu_deactivate(unsigned int cpu)
 	rq_lock_irqsave(rq, &rf);
 	if (rq->rd) {
 		BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
-		set_rq_offline(rq, RQ_ONOFF_HOTPLUG);
+		set_rq_offline(rq);
 	}
 	rq_unlock_irqrestore(rq, &rf);
 

kernel/sched/deadline.c

@@ -2606,7 +2606,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
 }
 
 /* Assumes rq->lock is held */
-static void rq_online_dl(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_online_dl(struct rq *rq)
 {
 	if (rq->dl.overloaded)
 		dl_set_overload(rq);
@@ -2617,7 +2617,7 @@ static void rq_online_dl(struct rq *rq, enum rq_onoff_reason reason)
 }
 
 /* Assumes rq->lock is held */
-static void rq_offline_dl(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_offline_dl(struct rq *rq)
 {
 	if (rq->dl.overloaded)
 		dl_clear_overload(rq);

kernel/sched/ext.c

@@ -3218,20 +3218,16 @@ static void handle_hotplug(struct rq *rq, bool online)
 			     online ? "online" : "offline");
 }
 
-static void rq_online_scx(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_online_scx(struct rq *rq)
 {
-	if (reason == RQ_ONOFF_HOTPLUG) {
-		handle_hotplug(rq, true);
-		rq->scx.flags |= SCX_RQ_ONLINE;
-	}
+	handle_hotplug(rq, true);
+	rq->scx.flags |= SCX_RQ_ONLINE;
 }
 
-static void rq_offline_scx(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_offline_scx(struct rq *rq)
 {
-	if (reason == RQ_ONOFF_HOTPLUG) {
-		rq->scx.flags &= ~SCX_RQ_ONLINE;
-		handle_hotplug(rq, false);
-	}
+	rq->scx.flags &= ~SCX_RQ_ONLINE;
+	handle_hotplug(rq, false);
 }
 
 #else	/* CONFIG_SMP */

kernel/sched/fair.c

@@ -12511,14 +12511,14 @@ void sched_balance_trigger(struct rq *rq)
 	nohz_balancer_kick(rq);
 }
 
-static void rq_online_fair(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_online_fair(struct rq *rq)
 {
 	update_sysctl();
 
 	update_runtime_enabled(rq);
 }
 
-static void rq_offline_fair(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_offline_fair(struct rq *rq)
 {
 	update_sysctl();
 

kernel/sched/rt.c

@@ -2425,7 +2425,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
 }
 
 /* Assumes rq->lock is held */
-static void rq_online_rt(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_online_rt(struct rq *rq)
 {
 	if (rq->rt.overloaded)
 		rt_set_overload(rq);
@@ -2436,7 +2436,7 @@ static void rq_online_rt(struct rq *rq, enum rq_onoff_reason reason)
 }
 
 /* Assumes rq->lock is held */
-static void rq_offline_rt(struct rq *rq, enum rq_onoff_reason reason)
+static void rq_offline_rt(struct rq *rq)
 {
 	if (rq->rt.overloaded)
 		rt_clear_overload(rq);

kernel/sched/sched.h

@@ -2328,11 +2328,6 @@ extern const u32		sched_prio_to_wmult[40];
 
 #define RETRY_TASK		((void *)-1UL)
 
-enum rq_onoff_reason {
-	RQ_ONOFF_HOTPLUG,		/* CPU is going on/offline */
-	RQ_ONOFF_TOPOLOGY,		/* sched domain topology update */
-};
-
 struct affinity_context {
 	const struct cpumask *new_mask;
 	struct cpumask *user_mask;
@@ -2371,8 +2366,8 @@ struct sched_class {
 
 	void (*set_cpus_allowed)(struct task_struct *p, struct affinity_context *ctx);
 
-	void (*rq_online)(struct rq *rq, enum rq_onoff_reason reason);
-	void (*rq_offline)(struct rq *rq, enum rq_onoff_reason reason);
+	void (*rq_online)(struct rq *rq);
+	void (*rq_offline)(struct rq *rq);
 
 	struct rq *(*find_lock_rq)(struct task_struct *p, struct rq *rq);
 #endif
@@ -2913,8 +2908,8 @@ static inline void double_rq_unlock(struct rq *rq1, struct rq *rq2)
 	raw_spin_rq_unlock(rq1);
 }
 
-extern void set_rq_online (struct rq *rq, enum rq_onoff_reason reason);
-extern void set_rq_offline(struct rq *rq, enum rq_onoff_reason reason);
+extern void set_rq_online (struct rq *rq);
+extern void set_rq_offline(struct rq *rq);
 extern bool sched_smp_initialized;
 
 #else /* CONFIG_SMP */

kernel/sched/topology.c

@@ -496,7 +496,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)
 		old_rd = rq->rd;
 
 		if (cpumask_test_cpu(rq->cpu, old_rd->online))
-			set_rq_offline(rq, RQ_ONOFF_TOPOLOGY);
+			set_rq_offline(rq);
 
 		cpumask_clear_cpu(rq->cpu, old_rd->span);
 
@@ -514,7 +514,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)
 
 	cpumask_set_cpu(rq->cpu, rd->span);
 	if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
-		set_rq_online(rq, RQ_ONOFF_TOPOLOGY);
+		set_rq_online(rq);
 
 	rq_unlock_irqrestore(rq, &rf);