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 <[email protected]> Acked-by: Peter Zijlstra <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Thomas Gleixner <[email protected]>
CamonZ · May 6, 2016 · aaddd7d · aaddd7d
1 parent f2785dd
commit aaddd7d
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Showing 2 changed files with 10 additions and 7 deletions.
diff --git 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
@@ -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 +1263,15 @@ static struct cpuhp_step cpuhp_ap_states[] = {
 	 * The dynamically registered state space is here
 	 */
 
+#ifdef CONFIG_SMP
+	/* Last state is scheduler control setting the cpu active */
+	[CPUHP_AP_ACTIVE] = {
+		.name			= "sched:active",
+		.startup		= sched_cpu_activate,
+		.teardown		= sched_cpu_deactivate,
+	},
+#endif
+
 	/* CPU is fully up and running. */
 	[CPUHP_ONLINE] = {
 		.name			= "online",