[patch 08/40] cpu: hotplug: Convert the hotplugged processor work to a state machine

[Thomas Gleixner <tglx@linutronix.de>]

[-- Attachment #1: cpu-hotplug-implement-starting-dying-statemachine.patch --]
[-- Type: text/plain, Size: 4417 bytes --]

Move the functions which need to run on the hotplugged processor into
a state machine array and let the code iterate through these functions.

In a later state, this will grow synchronization points between the
control processor and the hotplugged processor, so we can move the
various architecture implementations of the synchronizations to the
core.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/cpuhotplug.h |    4 ++
 kernel/cpu.c               |   70 +++++++++++++++++++++++++++++++++++----------
 2 files changed, 59 insertions(+), 15 deletions(-)

Index: linux-2.6/include/linux/cpuhotplug.h
===================================================================
--- linux-2.6.orig/include/linux/cpuhotplug.h
+++ linux-2.6/include/linux/cpuhotplug.h
@@ -7,6 +7,10 @@ enum cpuhp_states {
 	CPUHP_NOTIFY_PREPARE,
 	CPUHP_NOTIFY_DEAD,
 	CPUHP_BRINGUP_CPU,
+	CPUHP_AP_OFFLINE,
+	CPUHP_AP_NOTIFY_STARTING,
+	CPUHP_AP_NOTIFY_DYING,
+	CPUHP_AP_MAX,
 	CPUHP_TEARDOWN_CPU,
 	CPUHP_PERCPU_THREADS,
 	CPUHP_NOTIFY_ONLINE,
Index: linux-2.6/kernel/cpu.c
===================================================================
--- linux-2.6.orig/kernel/cpu.c
+++ linux-2.6/kernel/cpu.c
@@ -32,6 +32,7 @@ struct cpuhp_step {
 };
 
 static struct cpuhp_step cpuhp_bp_states[];
+static struct cpuhp_step cpuhp_ap_states[];
 
 #ifdef CONFIG_SMP
 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
@@ -216,6 +217,12 @@ static int bringup_cpu(unsigned int cpu)
 	return 0;
 }
 
+static int notify_starting(unsigned int cpu)
+{
+	cpu_notify(CPU_STARTING, cpu);
+	return 0;
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 EXPORT_SYMBOL(register_cpu_notifier);
 
@@ -303,17 +310,26 @@ static int notify_down_prepare(unsigned 
 	return err;
 }
 
+static int notify_dying(unsigned int cpu)
+{
+	cpu_notify(CPU_DYING, cpu);
+	return 0;
+}
+
 /* Take this CPU down. */
 static int __ref take_cpu_down(void *_param)
 {
-	int err, cpu = smp_processor_id();
+	int step, err, cpu = smp_processor_id();
 
 	/* Ensure this CPU doesn't handle any more interrupts. */
 	err = __cpu_disable();
 	if (err < 0)
 		return err;
 
-	cpu_notify(CPU_DYING, cpu);
+	for (step = CPUHP_AP_MAX; step >= CPUHP_AP_OFFLINE; step--) {
+		if (cpuhp_ap_states[step].teardown)
+			cpuhp_ap_states[step].teardown(cpu);
+	}
 	/* Park the stopper thread */
 	kthread_park(current);
 	return 0;
@@ -357,6 +373,7 @@ static int notify_dead(unsigned int cpu)
 #define notify_down_prepare	NULL
 #define takedown_cpu		NULL
 #define notify_dead		NULL
+#define notify_dying		NULL
 #endif
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -429,6 +446,24 @@ out:
 EXPORT_SYMBOL(cpu_down);
 #endif /*CONFIG_HOTPLUG_CPU*/
 
+/**
+ * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
+ * @cpu: cpu that just started
+ *
+ * This function calls the cpu_chain notifiers with CPU_STARTING.
+ * It must be called by the arch code on the new cpu, before the new cpu
+ * enables interrupts and before the "boot" cpu returns from __cpu_up().
+ */
+void notify_cpu_starting(unsigned int cpu)
+{
+	int step;
+
+	for (step = CPUHP_AP_OFFLINE; step <  CPUHP_AP_MAX; step++) {
+		if (cpuhp_ap_states[step].startup)
+			cpuhp_ap_states[step].startup(cpu);
+	}
+}
+
 static void undo_cpu_up(unsigned int cpu, int step)
 {
 	while (step--) {
@@ -703,19 +738,6 @@ core_initcall(cpu_hotplug_pm_sync_init);
 
 #endif /* CONFIG_PM_SLEEP_SMP */
 
-/**
- * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
- * @cpu: cpu that just started
- *
- * This function calls the cpu_chain notifiers with CPU_STARTING.
- * It must be called by the arch code on the new cpu, before the new cpu
- * enables interrupts and before the "boot" cpu returns from __cpu_up().
- */
-void __cpuinit notify_cpu_starting(unsigned int cpu)
-{
-	cpu_notify(CPU_STARTING, cpu);
-}
-
 #endif /* CONFIG_SMP */
 
 /* Boot processor state steps */
@@ -764,6 +786,24 @@ static struct cpuhp_step cpuhp_bp_states
 	},
 };
 
+/* Application processor state steps */
+static struct cpuhp_step cpuhp_ap_states[] = {
+#ifdef CONFIG_SMP
+	[CPUHP_AP_NOTIFY_STARTING] = {
+		.startup = notify_starting,
+		.teardown = NULL,
+	},
+	[CPUHP_AP_NOTIFY_DYING] = {
+		.startup = NULL,
+		.teardown = notify_dying,
+	},
+#endif
+	[CPUHP_MAX] = {
+		.startup = NULL,
+		.teardown = NULL,
+	},
+};
+
 /*
  * cpu_bit_bitmap[] is a special, "compressed" data structure that
  * represents all NR_CPUS bits binary values of 1<<nr.