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

Thomas Gleixner
2016-03-10T12:10:00Z

[-- Attachment #1: sched--Allow-hotplug-notifiers-to-be-setup-early.patch --]
[-- Type: text/plain, Size: 3589 bytes --]

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)
{