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Groups > linux.kernel > #1355075

[patch 04/15] sched: Allow hotplug notifiers to be setup early

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Prevent the SMP scheduler related notifiers to be executed before the smp
scheduler is initialized and install them early.

This is a preparatory change for further consolidation of the hotplug notifier
maze.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/sched/core.c |   59 +++++++++++++++++++++++++++++++---------------------
 1 file changed, 36 insertions(+), 23 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5256,6 +5256,8 @@ int task_can_attach(struct task_struct *
 
 #ifdef CONFIG_SMP
 
+static bool sched_smp_initialized __read_mostly;
+
 #ifdef CONFIG_NUMA_BALANCING
 /* Migrate current task p to target_cpu */
 int migrate_task_to(struct task_struct *p, int target_cpu)
@@ -5751,25 +5753,6 @@ int sched_cpu_starting(unsigned int cpu)
 	return 0;
 }
 
-static int __init migration_init(void)
-{
-	void *cpu = (void *)(long)smp_processor_id();
-	int err;
-
-	/* Initialize migration for the boot CPU */
-	err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
-	BUG_ON(err == NOTIFY_BAD);
-	migration_call(&migration_notifier, CPU_ONLINE, cpu);
-	register_cpu_notifier(&migration_notifier);
-
-	/* Register cpu active notifiers */
-	cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
-	cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
-
-	return 0;
-}
-early_initcall(migration_init);
-
 static cpumask_var_t sched_domains_tmpmask; /* sched_domains_mutex */
 
 #ifdef CONFIG_SCHED_DEBUG
@@ -6944,6 +6927,9 @@ static int sched_domains_numa_masks_upda
 {
 	int cpu = (long)hcpu;
 
+	if (!sched_smp_initialized)
+		return NOTIFY_DONE;
+
 	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_ONLINE:
 		sched_domains_numa_masks_set(cpu);
@@ -7362,6 +7348,9 @@ static int num_cpus_frozen;	/* used to m
 static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
 			     void *hcpu)
 {
+	if (!sched_smp_initialized)
+		return NOTIFY_DONE;
+
 	switch (action) {
 	case CPU_ONLINE_FROZEN:
 	case CPU_DOWN_FAILED_FROZEN:
@@ -7402,6 +7391,9 @@ static int cpuset_cpu_inactive(struct no
 	bool overflow;
 	int cpus;
 
+	if (!sched_smp_initialized)
+		return NOTIFY_DONE;
+
 	switch (action) {
 	case CPU_DOWN_PREPARE:
 		rcu_read_lock_sched();
@@ -7449,10 +7441,6 @@ void __init sched_init_smp(void)
 		cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
 	mutex_unlock(&sched_domains_mutex);
 
-	hotcpu_notifier(sched_domains_numa_masks_update, CPU_PRI_SCHED_ACTIVE);
-	hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
-	hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
-
 	init_hrtick();
 
 	/* Move init over to a non-isolated CPU */
@@ -7463,7 +7451,32 @@ void __init sched_init_smp(void)
 
 	init_sched_rt_class();
 	init_sched_dl_class();
+	sched_smp_initialized = true;
 }
+
+static int __init migration_init(void)
+{
+	void *cpu = (void *)(long)smp_processor_id();
+	int err;
+
+	/* Initialize migration for the boot CPU */
+	err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
+	BUG_ON(err == NOTIFY_BAD);
+	migration_call(&migration_notifier, CPU_ONLINE, cpu);
+	register_cpu_notifier(&migration_notifier);
+
+	/* Register cpu active notifiers */
+	cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
+	cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
+
+	hotcpu_notifier(sched_domains_numa_masks_update, CPU_PRI_SCHED_ACTIVE);
+	hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
+	hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
+
+	return 0;
+}
+early_initcall(migration_init);
+
 #else
 void __init sched_init_smp(void)
 {

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[patch 00/15] cpu/hotplug: Convert scheduler to hotplug state machine Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 14/15] sched/fair: Make ilb_notifier an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 07/15] sched/hotplug: Convert cpu_[in]active notifiers to  state machine Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 01/15] cpu/hotplug: Document states better Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 10/15] sched/migration: Move calc_load_migrate() into CPU_DYING Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 13/15] sched/hotplug: Make activate() the last hotplug step Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 05/15] sched: Consolidate the notifier maze Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 09/15] sched/migration: Move prepare transition to  SCHED_STARTING state Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 08/15] sched,  hotplug: Move sync_rcu to be with set_cpu_active(false) Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 06/15] sched: Move sched_domains_numa_masks_clear() to  DOWN_PREPARE Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 11/15] sched/migration: Move CPU_ONLINE into scheduler state Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 03/15] sched: Make set_cpu_rq_start_time() a built in hotplug  state Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 12/15] sched/hotplug: Move migration CPU_DYING to  sched_cpu_dying() Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 15/15] sched: Make hrtick_notifier an explicit call Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:10 +0100
  [patch 04/15] sched: Allow hotplug notifiers to be setup early Thomas Gleixner <tglx@linutronix.de> - 2016-03-10 13:20 +0100

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