sched: Allow hotplug notifiers to be setup early

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>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4df9aaae27a23808f5d5068cafa68eb50bcf1b0b..328502c9af0004aade82e45308b8baa3a26e4b0a 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5195,6 +5195,8 @@ out:
 
 #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)
@@ -5513,25 +5515,6 @@ 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
@@ -6711,6 +6694,9 @@ static int sched_domains_numa_masks_update(struct notifier_block *nfb,
 {
        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);
@@ -7129,6 +7115,9 @@ static int num_cpus_frozen;       /* used to mark begin/end of suspend/resume */
 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:
@@ -7169,6 +7158,9 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
        bool overflow;
        int cpus;
 
+       if (!sched_smp_initialized)
+               return NOTIFY_DONE;
+
        switch (action) {
        case CPU_DOWN_PREPARE:
                rcu_read_lock_sched();
@@ -7216,10 +7208,6 @@ 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 */
@@ -7230,7 +7218,32 @@ 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)
 {