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Subject[PATCH]sched: Add comments for ifdefs in sched.c
Hi,

I was going to through sched.c after some time, and found it really
tough to read through it with the number of ifdefs. Adding some comments
marking the #else and #endif for what they are (not) defining.

Thanks,
--
sched: Add comments for ifdefs in sched.c

sched.c is quite difficult to read anyway. With the number of ifdefs
especially those of the nested variety, it was a bigger challenge. This
patch finds and comments some of those ifdefs.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c 2008-05-12 11:03:59.000000000 +0530
+++ linux-2.6/kernel/sched.c 2008-05-12 13:52:07.000000000 +0530
@@ -289,15 +289,15 @@ 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.
@@ -307,9 +307,9 @@ 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.
@@ -434,8 +434,8 @@ struct cfs_rq {
*/
unsigned long task_weight;
} aggregate;
-#endif
-#endif
+#endif /* CONFIG_SMP */
+#endif /* CONFIG_FAIR_GROUP_SCHED */
};

/* Real-Time classes' related field in a runqueue: */
@@ -1345,15 +1345,15 @@ 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)
@@ -2463,7 +2463,7 @@ static int try_to_wake_up(struct task_st
}
}
}
-#endif
+#endif /* CONFIG_SCHEDSTATS */

out_activate:
#endif /* CONFIG_SMP */
@@ -2663,7 +2663,7 @@ fire_sched_out_preempt_notifiers(struct
notifier->ops->sched_out(notifier, next);
}

-#else
+#else /* !CONFIG_PREEMPT_NOTIFIERS */

static void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
@@ -2675,7 +2675,7 @@ fire_sched_out_preempt_notifiers(struct
{
}

-#endif
+#endif /* CONFIG_PREEMPT_NOTIFIERS */

/**
* prepare_task_switch - prepare to switch tasks
@@ -6635,9 +6635,9 @@ static void sched_domain_debug(struct sc
}
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)
{
@@ -6931,7 +6931,7 @@ static void sched_domain_node_span(int n
cpus_or(*span, *span, *nodemask);
}
}
-#endif
+#endif /* CONFIG_NUMA */

int sched_smt_power_savings = 0, sched_mc_power_savings = 0;

@@ -6950,7 +6950,7 @@ cpu_to_cpu_group(int cpu, const cpumask_
*sg = &per_cpu(sched_group_cpus, cpu);
return cpu;
}
-#endif
+#endif /* CONFIG_SCHED_SMT */

/*
* multi-core sched-domains:
@@ -6958,7 +6958,7 @@ cpu_to_cpu_group(int cpu, const cpumask_
#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
@@ -7060,7 +7060,7 @@ static void init_numa_sched_groups_power
sg = sg->next;
} while (sg != group_head);
}
-#endif
+#endif /* CONFIG_NUMA */

#ifdef CONFIG_NUMA
/* Free memory allocated for various sched_group structures */
@@ -7097,11 +7097,11 @@ 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.
@@ -7797,7 +7797,7 @@ int sched_create_sysfs_power_savings_ent
#endif
return err;
}
-#endif
+#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */

/*
* Force a reinitialization of the sched domains hierarchy. The domains
@@ -8014,8 +8014,8 @@ 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 **);
@@ -8029,8 +8029,8 @@ 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
@@ -8047,8 +8047,8 @@ 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);
@@ -8058,8 +8058,8 @@ 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;
@@ -8378,7 +8378,7 @@ static inline void unregister_fair_sched
{
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)
{
}
@@ -8396,7 +8396,7 @@ static inline void register_fair_sched_g
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)
@@ -8467,7 +8467,7 @@ static inline void unregister_rt_sched_g
{
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)
{
}
@@ -8485,7 +8485,7 @@ static inline void register_rt_sched_gro
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)
@@ -8596,7 +8596,7 @@ void sched_move_task(struct task_struct

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)
@@ -8857,7 +8857,7 @@ static int sched_rt_global_constraints(v

return ret;
}
-#else
+#else /* !CONFIG_RT_GROUP_SCHED */
static int sched_rt_global_constraints(void)
{
unsigned long flags;
@@ -8875,7 +8875,7 @@ static int sched_rt_global_constraints(v

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,
@@ -8983,7 +8983,7 @@ static u64 cpu_shares_read_u64(struct cg

return (u64) tg->shares;
}
-#endif
+#endif /* CONFIG_FAIR_GROUP_SCHED */

#ifdef CONFIG_RT_GROUP_SCHED
static ssize_t cpu_rt_runtime_write(struct cgroup *cgrp, struct cftype *cft,
@@ -9007,7 +9007,7 @@ static u64 cpu_rt_period_read_uint(struc
{
return sched_group_rt_period(cgroup_tg(cgrp));
}
-#endif
+#endif /* CONFIG_RT_GROUP_SCHED */

static struct cftype cpu_files[] = {
#ifdef CONFIG_FAIR_GROUP_SCHED
--
regards,
Dhaval

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