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Commit 41c7ce9a authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

[PATCH] sched: null domains 



Fix the last 2 places that directly access a runqueue's sched-domain and
assume it cannot be NULL.

That allows the use of NULL for domain, instead of a dummy domain, to signify
no balancing is to happen.  No functional changes.

Signed-off-by: default avatarNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4866cde0

kernel/sched.c

+21 −15
Original line number Diff line number Diff line
@@ -2579,11 +2579,15 @@ out: 
#ifdef CONFIG_SCHED_SMT

static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)

{

	struct sched_domain *sd = this_rq->sd;

	struct sched_domain *tmp, *sd = NULL;

	cpumask_t sibling_map;

	int i;



	if (!(sd->flags & SD_SHARE_CPUPOWER))

	for_each_domain(this_cpu, tmp)

		if (tmp->flags & SD_SHARE_CPUPOWER)

			sd = tmp;



	if (!sd)

		return;



	/*
@@ -2624,13 +2628,17 @@ static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq) 


static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)

{

	struct sched_domain *sd = this_rq->sd;

	struct sched_domain *tmp, *sd = NULL;

	cpumask_t sibling_map;

	prio_array_t *array;

	int ret = 0, i;

	task_t *p;



	if (!(sd->flags & SD_SHARE_CPUPOWER))

	for_each_domain(this_cpu, tmp)

		if (tmp->flags & SD_SHARE_CPUPOWER)

			sd = tmp;



	if (!sd)

		return 0;



	/*
@@ -4617,6 +4625,11 @@ static void sched_domain_debug(struct sched_domain *sd, int cpu) 
{

	int level = 0;



	if (!sd) {

		printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);

		return;

	}



	printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);



	do {
@@ -4874,7 +4887,7 @@ static void __devinit arch_init_sched_domains(void) 
	cpus_and(cpu_default_map, cpu_default_map, cpu_online_map);



	/*

	 * Set up domains. Isolated domains just stay on the dummy domain.

	 * Set up domains. Isolated domains just stay on the NULL domain.

	 */

	for_each_cpu_mask(i, cpu_default_map) {

		int group;
@@ -4987,18 +5000,11 @@ static void __devinit arch_destroy_sched_domains(void) 


#endif /* ARCH_HAS_SCHED_DOMAIN */



/*

 * Initial dummy domain for early boot and for hotplug cpu. Being static,

 * it is initialized to zero, so all balancing flags are cleared which is

 * what we want.

 */

static struct sched_domain sched_domain_dummy;



#ifdef CONFIG_HOTPLUG_CPU

/*

 * Force a reinitialization of the sched domains hierarchy.  The domains

 * and groups cannot be updated in place without racing with the balancing

 * code, so we temporarily attach all running cpus to a "dummy" domain

 * code, so we temporarily attach all running cpus to the NULL domain

 * which will prevent rebalancing while the sched domains are recalculated.

 */

static int update_sched_domains(struct notifier_block *nfb,
@@ -5010,7 +5016,7 @@ static int update_sched_domains(struct notifier_block *nfb, 
	case CPU_UP_PREPARE:

	case CPU_DOWN_PREPARE:

		for_each_online_cpu(i)

			cpu_attach_domain(&sched_domain_dummy, i);

			cpu_attach_domain(NULL, i);

		arch_destroy_sched_domains();

		return NOTIFY_OK;
@@ -5072,7 +5078,7 @@ void __init sched_init(void) 
		rq->best_expired_prio = MAX_PRIO;



#ifdef CONFIG_SMP

		rq->sd = &sched_domain_dummy;

		rq->sd = NULL;

		for (j = 1; j < 3; j++)

			rq->cpu_load[j] = 0;

		rq->active_balance = 0;