[patch 12/20] cpu/hotplug: Move scheduler cpu_online notifier to hotplug core

[Thomas Gleixner]

Move the scheduler cpu online notifier part to the hotplug core. This is
anyway the highest priority callback and we need that functionality right now
for the next changes.

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
 include/linux/cpuhotplug.h |    1 +
 kernel/cpu.c               |   18 ++++++++++++++++++
 kernel/sched/core.c        |   10 ----------
 3 files changed, 19 insertions(+), 10 deletions(-)

Index: b/include/linux/cpuhotplug.h
===================================================================
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -10,6 +10,7 @@ enum cpuhp_state {
        CPUHP_AP_NOTIFY_STARTING,
        CPUHP_AP_ONLINE,
        CPUHP_TEARDOWN_CPU,
+       CPUHP_CPU_SET_ACTIVE,
        CPUHP_NOTIFY_ONLINE,
        CPUHP_ONLINE_DYN,
        CPUHP_ONLINE_DYN_END            = CPUHP_ONLINE_DYN + 30,
Index: b/kernel/cpu.c
===================================================================
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -666,6 +666,19 @@ void notify_cpu_starting(unsigned int cp
        }
 }
 
+/*
+ * Called from the idle task. We need to set active here, so we can kick off
+ * the stopper thread.
+ */
+static int cpuhp_set_cpu_active(unsigned int cpu)
+{
+       /* The cpu is marked online, set it active now */
+       set_cpu_active(cpu, true);
+       /* Unpark the stopper thread */
+       stop_machine_unpark(cpu);
+       return 0;
+}
+
 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
 {
        for (st->state--; st->state > st->target; st->state--) {
@@ -941,6 +954,11 @@ static struct cpuhp_step cpuhp_bp_states
                .teardown               = takedown_cpu,
                .cant_stop              = true,
        },
+       [CPUHP_CPU_SET_ACTIVE] = {
+               .name                   = "cpu:active",
+               .startup                = cpuhp_set_cpu_active,
+               .teardown               = NULL,
+       },
        [CPUHP_NOTIFY_ONLINE] = {
                .name                   = "notify:online",
                .startup                = notify_online,
Index: b/kernel/sched/core.c
===================================================================
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5692,16 +5692,6 @@ static int sched_cpu_active(struct notif
                set_cpu_rq_start_time();
                return NOTIFY_OK;
 
-       case CPU_ONLINE:
-               /*
-                * At this point a starting CPU has marked itself as online via
-                * set_cpu_online(). But it might not yet have marked itself
-                * as active, which is essential from here on.
-                */
-               set_cpu_active(cpu, true);
-               stop_machine_unpark(cpu);
-               return NOTIFY_OK;
-
        case CPU_DOWN_FAILED:
                set_cpu_active(cpu, true);
                return NOTIFY_OK;