sched: add comments for ifdefs in sched.c

make sched.c easier to read.
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/sched.c

@@ -292,15 +292,15 @@ struct task_group root_task_group;
 static DEFINE_PER_CPU(struct sched_entity, init_sched_entity);
 /* Default task group's cfs_rq on each cpu */
 static DEFINE_PER_CPU(struct cfs_rq, init_cfs_rq) ____cacheline_aligned_in_smp;
-#endif
+#endif /* CONFIG_FAIR_GROUP_SCHED */
 
 #ifdef CONFIG_RT_GROUP_SCHED
 static DEFINE_PER_CPU(struct sched_rt_entity, init_sched_rt_entity);
 static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp;
-#endif
-#else
+#endif /* CONFIG_RT_GROUP_SCHED */
+#else /* !CONFIG_FAIR_GROUP_SCHED */
 #define root_task_group init_task_group
-#endif
+#endif /* CONFIG_FAIR_GROUP_SCHED */
 
 /* task_group_lock serializes add/remove of task groups and also changes to
  * a task group's cpu shares.
@@ -310,9 +310,9 @@ static DEFINE_SPINLOCK(task_group_lock);
 #ifdef CONFIG_FAIR_GROUP_SCHED
 #ifdef CONFIG_USER_SCHED
 # define INIT_TASK_GROUP_LOAD	(2*NICE_0_LOAD)
-#else
+#else /* !CONFIG_USER_SCHED */
 # define INIT_TASK_GROUP_LOAD	NICE_0_LOAD
-#endif
+#endif /* CONFIG_USER_SCHED */
 
 /*
  * A weight of 0, 1 or ULONG_MAX can cause arithmetics problems.
@@ -1316,15 +1316,15 @@ void wake_up_idle_cpu(int cpu)
 	if (!tsk_is_polling(rq->idle))
 		smp_send_reschedule(cpu);
 }
-#endif
+#endif /* CONFIG_NO_HZ */
 
-#else
+#else /* !CONFIG_SMP */
 static void __resched_task(struct task_struct *p, int tif_bit)
 {
 	assert_spin_locked(&task_rq(p)->lock);
 	set_tsk_thread_flag(p, tif_bit);
 }
-#endif
+#endif /* CONFIG_SMP */
 
 #if BITS_PER_LONG == 32
 # define WMULT_CONST	(~0UL)
@@ -2129,7 +2129,7 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
 			}
 		}
 	}
-#endif
+#endif /* CONFIG_SCHEDSTATS */
 
 out_activate:
 #endif /* CONFIG_SMP */
@@ -2329,7 +2329,7 @@ fire_sched_out_preempt_notifiers(struct task_struct *curr,
 		notifier->ops->sched_out(notifier, next);
 }
 
-#else
+#else /* !CONFIG_PREEMPT_NOTIFIERS */
 
 static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
 {
@@ -2341,7 +2341,7 @@ fire_sched_out_preempt_notifiers(struct task_struct *curr,
 {
 }
 
-#endif
+#endif /* CONFIG_PREEMPT_NOTIFIERS */
 
 /**
  * prepare_task_switch - prepare to switch tasks
@@ -6300,9 +6300,9 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu)
 	}
 	kfree(groupmask);
 }
-#else
+#else /* !CONFIG_SCHED_DEBUG */
 # define sched_domain_debug(sd, cpu) do { } while (0)
-#endif
+#endif /* CONFIG_SCHED_DEBUG */
 
 static int sd_degenerate(struct sched_domain *sd)
 {
@@ -6598,7 +6598,7 @@ static void sched_domain_node_span(int node, cpumask_t *span)
 		cpus_or(*span, *span, *nodemask);
 	}
 }
-#endif
+#endif /* CONFIG_NUMA */
 
 int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
 
@@ -6617,7 +6617,7 @@ cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
 		*sg = &per_cpu(sched_group_cpus, cpu);
 	return cpu;
 }
-#endif
+#endif /* CONFIG_SCHED_SMT */
 
 /*
  * multi-core sched-domains:
@@ -6625,7 +6625,7 @@ cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map, struct sched_group **sg,
 #ifdef CONFIG_SCHED_MC
 static DEFINE_PER_CPU(struct sched_domain, core_domains);
 static DEFINE_PER_CPU(struct sched_group, sched_group_core);
-#endif
+#endif /* CONFIG_SCHED_MC */
 
 #if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
 static int
@@ -6727,7 +6727,7 @@ static void init_numa_sched_groups_power(struct sched_group *group_head)
 		sg = sg->next;
 	} while (sg != group_head);
 }
-#endif
+#endif /* CONFIG_NUMA */
 
 #ifdef CONFIG_NUMA
 /* Free memory allocated for various sched_group structures */
@@ -6764,11 +6764,11 @@ next_sg:
 		sched_group_nodes_bycpu[cpu] = NULL;
 	}
 }
-#else
+#else /* !CONFIG_NUMA */
 static void free_sched_groups(const cpumask_t *cpu_map, cpumask_t *nodemask)
 {
 }
-#endif
+#endif /* CONFIG_NUMA */
 
 /*
  * Initialize sched groups cpu_power.
@@ -7459,7 +7459,7 @@ int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
 #endif
 	return err;
 }
-#endif
+#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
 
 /*
  * Force a reinitialization of the sched domains hierarchy. The domains
@@ -7677,8 +7677,8 @@ void __init sched_init(void)
 
 		root_task_group.cfs_rq = (struct cfs_rq **)ptr;
 		ptr += nr_cpu_ids * sizeof(void **);
-#endif
-#endif
+#endif /* CONFIG_USER_SCHED */
+#endif /* CONFIG_FAIR_GROUP_SCHED */
 #ifdef CONFIG_RT_GROUP_SCHED
 		init_task_group.rt_se = (struct sched_rt_entity **)ptr;
 		ptr += nr_cpu_ids * sizeof(void **);
@@ -7692,8 +7692,8 @@ void __init sched_init(void)
 
 		root_task_group.rt_rq = (struct rt_rq **)ptr;
 		ptr += nr_cpu_ids * sizeof(void **);
-#endif
-#endif
+#endif /* CONFIG_USER_SCHED */
+#endif /* CONFIG_RT_GROUP_SCHED */
 	}
 
 #ifdef CONFIG_SMP
@@ -7709,8 +7709,8 @@ void __init sched_init(void)
 #ifdef CONFIG_USER_SCHED
 	init_rt_bandwidth(&root_task_group.rt_bandwidth,
 			global_rt_period(), RUNTIME_INF);
-#endif
-#endif
+#endif /* CONFIG_USER_SCHED */
+#endif /* CONFIG_RT_GROUP_SCHED */
 
 #ifdef CONFIG_GROUP_SCHED
 	list_add(&init_task_group.list, &task_groups);
@@ -7720,8 +7720,8 @@ void __init sched_init(void)
 	INIT_LIST_HEAD(&root_task_group.children);
 	init_task_group.parent = &root_task_group;
 	list_add(&init_task_group.siblings, &root_task_group.children);
-#endif
-#endif
+#endif /* CONFIG_USER_SCHED */
+#endif /* CONFIG_GROUP_SCHED */
 
 	for_each_possible_cpu(i) {
 		struct rq *rq;
@@ -8040,7 +8040,7 @@ static inline void unregister_fair_sched_group(struct task_group *tg, int cpu)
 {
 	list_del_rcu(&tg->cfs_rq[cpu]->leaf_cfs_rq_list);
 }
-#else
+#else /* !CONFG_FAIR_GROUP_SCHED */
 static inline void free_fair_sched_group(struct task_group *tg)
 {
 }
@@ -8058,7 +8058,7 @@ static inline void register_fair_sched_group(struct task_group *tg, int cpu)
 static inline void unregister_fair_sched_group(struct task_group *tg, int cpu)
 {
 }
-#endif
+#endif /* CONFIG_FAIR_GROUP_SCHED */
 
 #ifdef CONFIG_RT_GROUP_SCHED
 static void free_rt_sched_group(struct task_group *tg)
@@ -8129,7 +8129,7 @@ static inline void unregister_rt_sched_group(struct task_group *tg, int cpu)
 {
 	list_del_rcu(&tg->rt_rq[cpu]->leaf_rt_rq_list);
 }
-#else
+#else /* !CONFIG_RT_GROUP_SCHED */
 static inline void free_rt_sched_group(struct task_group *tg)
 {
 }
@@ -8147,7 +8147,7 @@ static inline void register_rt_sched_group(struct task_group *tg, int cpu)
 static inline void unregister_rt_sched_group(struct task_group *tg, int cpu)
 {
 }
-#endif
+#endif /* CONFIG_RT_GROUP_SCHED */
 
 #ifdef CONFIG_GROUP_SCHED
 static void free_sched_group(struct task_group *tg)
@@ -8258,7 +8258,7 @@ void sched_move_task(struct task_struct *tsk)
 
 	task_rq_unlock(rq, &flags);
 }
-#endif
+#endif /* CONFIG_GROUP_SCHED */
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void set_se_shares(struct sched_entity *se, unsigned long shares)
@@ -8508,7 +8508,7 @@ static int sched_rt_global_constraints(void)
 
 	return ret;
 }
-#else
+#else /* !CONFIG_RT_GROUP_SCHED */
 static int sched_rt_global_constraints(void)
 {
 	unsigned long flags;
@@ -8526,7 +8526,7 @@ static int sched_rt_global_constraints(void)
 
 	return 0;
 }
-#endif
+#endif /* CONFIG_RT_GROUP_SCHED */
 
 int sched_rt_handler(struct ctl_table *table, int write,
 		struct file *filp, void __user *buffer, size_t *lenp,
@@ -8634,7 +8634,7 @@ static u64 cpu_shares_read_u64(struct cgroup *cgrp, struct cftype *cft)
 
 	return (u64) tg->shares;
 }
-#endif
+#endif /* CONFIG_FAIR_GROUP_SCHED */
 
 #ifdef CONFIG_RT_GROUP_SCHED
 static int cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
@@ -8658,7 +8658,7 @@ static u64 cpu_rt_period_read_uint(struct cgroup *cgrp, struct cftype *cft)
 {
 	return sched_group_rt_period(cgroup_tg(cgrp));
 }
-#endif
+#endif /* CONFIG_RT_GROUP_SCHED */
 
 static struct cftype cpu_files[] = {
 #ifdef CONFIG_FAIR_GROUP_SCHED