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[tip:smp/hotplug] sched/hotplug: Make activate() the last hotplug step

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  [tip:smp/hotplug] sched/hotplug: Make activate() the last hotplug  step tip-bot for Thomas Gleixner <tipbot@zytor.com> - 2016-05-05 13:30 +0200

#1395049 — [tip:smp/hotplug] sched/hotplug: Make activate() the last hotplug step

Commit-ID:  b4f43a28647291a7dc1773924b77bc5ee7eccb16
Gitweb:     http://git.kernel.org/tip/b4f43a28647291a7dc1773924b77bc5ee7eccb16
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 10 Mar 2016 12:54:19 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 5 May 2016 13:17:54 +0200

sched/hotplug: Make activate() the last hotplug step

The scheduler can handle per cpu threads before the cpu is set to active and
it does not allow user space threads on the cpu before active is
set. Attaching to the scheduling domains is also not required before user
space threads can be handled.

Move the activation to the end of the hotplug state space. That also means
that deactivation is the first action when a cpu is shut down.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160310120025.597477199@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
 include/linux/cpuhotplug.h |  2 +-
 kernel/cpu.c               | 13 +++++++------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 9e07468..386374d 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -13,11 +13,11 @@ enum cpuhp_state {
 	CPUHP_AP_ONLINE,
 	CPUHP_TEARDOWN_CPU,
 	CPUHP_AP_ONLINE_IDLE,
-	CPUHP_AP_ACTIVE,
 	CPUHP_AP_SMPBOOT_THREADS,
 	CPUHP_AP_NOTIFY_ONLINE,
 	CPUHP_AP_ONLINE_DYN,
 	CPUHP_AP_ONLINE_DYN_END		= CPUHP_AP_ONLINE_DYN + 30,
+	CPUHP_AP_ACTIVE,
 	CPUHP_ONLINE,
 };
 
diff --git a/kernel/cpu.c b/kernel/cpu.c
index d6eeb8c..6180dd6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1242,12 +1242,6 @@ static struct cpuhp_step cpuhp_ap_states[] = {
 	[CPUHP_AP_ONLINE] = {
 		.name			= "ap:online",
 	},
-	/* First state is scheduler control. Interrupts are enabled */
-	[CPUHP_AP_ACTIVE] = {
-		.name			= "sched:active",
-		.startup		= sched_cpu_activate,
-		.teardown		= sched_cpu_deactivate,
-	},
 	/* Handle smpboot threads park/unpark */
 	[CPUHP_AP_SMPBOOT_THREADS] = {
 		.name			= "smpboot:threads",
@@ -1269,6 +1263,13 @@ static struct cpuhp_step cpuhp_ap_states[] = {
 	 * The dynamically registered state space is here
 	 */
 
+	/* Last state is scheduler control setting the cpu active */
+	[CPUHP_AP_ACTIVE] = {
+		.name			= "sched:active",
+		.startup		= sched_cpu_activate,
+		.teardown		= sched_cpu_deactivate,
+	},
+
 	/* CPU is fully up and running. */
 	[CPUHP_ONLINE] = {
 		.name			= "online",

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