sched: Restore previous implementation of check_for_migration()

commit 3bda2b55b4 ("Merge android-4.4.96 (aed4c54) into msm-4.4")
replaced HMP scheduler check_for_migration() implementation with
EAS scheduler implementation. This breaks HMP scheduler upmgiration
functionality. Fix this by restoring the previous implementation.

Change-Id: I3221f3efe42e1e43f8009cfa52c11afbb9d9c5b3
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>

kernel/sched/fair.c

@@ -3657,6 +3657,68 @@ static inline int migration_needed(struct task_struct *p, int cpu)
 	return 0;
 }
 
+static inline int
+kick_active_balance(struct rq *rq, struct task_struct *p, int new_cpu)
+{
+	unsigned long flags;
+	int rc = 0;
+
+	/* Invoke active balance to force migrate currently running task */
+	raw_spin_lock_irqsave(&rq->lock, flags);
+	if (!rq->active_balance) {
+		rq->active_balance = 1;
+		rq->push_cpu = new_cpu;
+		get_task_struct(p);
+		rq->push_task = p;
+		rc = 1;
+	}
+	raw_spin_unlock_irqrestore(&rq->lock, flags);
+
+	return rc;
+}
+
+static DEFINE_RAW_SPINLOCK(migration_lock);
+
+static bool do_migration(int reason, int new_cpu, int cpu)
+{
+	if ((reason == UP_MIGRATION || reason == DOWN_MIGRATION)
+				&& same_cluster(new_cpu, cpu))
+		return false;
+
+	/* Inter cluster high irqload migrations are OK */
+	return new_cpu != cpu;
+}
+
+/*
+ * Check if currently running task should be migrated to a better cpu.
+ *
+ * Todo: Effect this via changes to nohz_balancer_kick() and load balance?
+ */
+void check_for_migration(struct rq *rq, struct task_struct *p)
+{
+	int cpu = cpu_of(rq), new_cpu;
+	int active_balance = 0, reason;
+
+	reason = migration_needed(p, cpu);
+	if (!reason)
+		return;
+
+	raw_spin_lock(&migration_lock);
+	new_cpu = select_best_cpu(p, cpu, reason, 0);
+
+	if (do_migration(reason, new_cpu, cpu)) {
+		active_balance = kick_active_balance(rq, p, new_cpu);
+		if (active_balance)
+			mark_reserved(new_cpu);
+	}
+
+	raw_spin_unlock(&migration_lock);
+
+	if (active_balance)
+		stop_one_cpu_nowait(cpu, active_load_balance_cpu_stop, rq,
+					&rq->active_balance_work);
+}
+
 #ifdef CONFIG_CFS_BANDWIDTH
 
 static void init_cfs_rq_hmp_stats(struct cfs_rq *cfs_rq)
@@ -11436,47 +11498,6 @@ static void rq_offline_fair(struct rq *rq)
 	unthrottle_offline_cfs_rqs(rq);
 }
 
-static inline int
-kick_active_balance(struct rq *rq, struct task_struct *p, int new_cpu)
-{
-	int rc = 0;
-
-	/* Invoke active balance to force migrate currently running task */
-	raw_spin_lock(&rq->lock);
-	if (!rq->active_balance) {
-		rq->active_balance = 1;
-		rq->push_cpu = new_cpu;
-		get_task_struct(p);
-		rq->push_task = p;
-		rc = 1;
-	}
-	raw_spin_unlock(&rq->lock);
-
-	return rc;
-}
-
-void check_for_migration(struct rq *rq, struct task_struct *p)
-{
-	int new_cpu;
-	int active_balance;
-	int cpu = task_cpu(p);
-
-	if (rq->misfit_task) {
-		if (rq->curr->state != TASK_RUNNING ||
-		    rq->curr->nr_cpus_allowed == 1)
-			return;
-
-		new_cpu = select_energy_cpu_brute(p, cpu, 0);
-		if (capacity_orig_of(new_cpu) > capacity_orig_of(cpu)) {
-			active_balance = kick_active_balance(rq, p, new_cpu);
-			if (active_balance)
-				stop_one_cpu_nowait(cpu,
-						active_load_balance_cpu_stop,
-						rq, &rq->active_balance_work);
-		}
-	}
-}
-
 #endif /* CONFIG_SMP */
 
 /*

kernel/sched/sched.h

@@ -32,10 +32,8 @@ extern long calc_load_fold_active(struct rq *this_rq);
 
 #ifdef CONFIG_SMP
 extern void update_cpu_load_active(struct rq *this_rq);
-extern void check_for_migration(struct rq *rq, struct task_struct *p);
 #else
 static inline void update_cpu_load_active(struct rq *this_rq) { }
-static inline void check_for_migration(struct rq *rq, struct task_struct *p) { }
 #endif
 
 /*
@@ -1449,6 +1447,7 @@ static inline bool is_short_burst_task(struct task_struct *p)
 	       p->ravg.avg_sleep_time > sysctl_sched_short_sleep;
 }
 
+extern void check_for_migration(struct rq *rq, struct task_struct *p);
 extern void pre_big_task_count_change(const struct cpumask *cpus);
 extern void post_big_task_count_change(const struct cpumask *cpus);
 extern void set_hmp_defaults(void);
@@ -1708,6 +1707,7 @@ static inline int same_freq_domain(int src_cpu, int dst_cpu)
 	return 1;
 }
 
+static inline void check_for_migration(struct rq *rq, struct task_struct *p) { }
 static inline void pre_big_task_count_change(void) { }
 static inline void post_big_task_count_change(void) { }
 static inline void set_hmp_defaults(void) { }