From 949338e35131c551f7bf54f48a2e3a227af6721b Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 26 Feb 2016 18:43:35 +0000
Subject: [PATCH] cpu/hotplug: Move scheduler cpu_online notifier to hotplug
 core

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 <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.200791046@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/cpuhotplug.h |  1 +
 kernel/cpu.c               | 18 ++++++++++++++++++
 kernel/sched/core.c        | 10 ----------
 3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 29935261b26d..2f2e5d9711c4 100644
--- 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,
diff --git a/kernel/cpu.c b/kernel/cpu.c
index b5eacb9587af..65e34d34ca93 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -666,6 +666,19 @@ void notify_cpu_starting(unsigned int cpu)
 	}
 }
 
+/*
+ * 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,
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9503d590e5ef..626646396ca0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5692,16 +5692,6 @@ static int sched_cpu_active(struct notifier_block *nfb,
 		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;