[PATCH 02/20] x86/cpuid: Convert to hotplug state machine

[Sebastian Andrzej Siewior]

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Cc: x86@xxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/kernel/cpuid.c    | 54 ++++++++--------------------------------------
 include/linux/cpuhotplug.h |  1 +
 2 files changed, 10 insertions(+), 45 deletions(-)

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 2836de390f95..eaa272454fe4 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -115,7 +115,7 @@ static const struct file_operations cpuid_fops = {
 	.open = cpuid_open,
 };
 
-static int cpuid_device_create(int cpu)
+static int cpuid_device_create(unsigned int cpu)
 {
 	struct device *dev;
 
@@ -124,35 +124,12 @@ static int cpuid_device_create(int cpu)
 	return PTR_ERR_OR_ZERO(dev);
 }
 
-static void cpuid_device_destroy(int cpu)
+static int cpuid_device_destroy(unsigned int cpu)
 {
 	device_destroy(cpuid_class, MKDEV(CPUID_MAJOR, cpu));
+	return 0;
 }
 
-static int cpuid_class_cpu_callback(struct notifier_block *nfb,
-				    unsigned long action, void *hcpu)
-{
-	unsigned int cpu = (unsigned long)hcpu;
-	int err = 0;
-
-	switch (action) {
-	case CPU_UP_PREPARE:
-		err = cpuid_device_create(cpu);
-		break;
-	case CPU_UP_CANCELED:
-	case CPU_UP_CANCELED_FROZEN:
-	case CPU_DEAD:
-		cpuid_device_destroy(cpu);
-		break;
-	}
-	return notifier_from_errno(err);
-}
-
-static struct notifier_block cpuid_class_cpu_notifier =
-{
-	.notifier_call = cpuid_class_cpu_callback,
-};
-
 static char *cpuid_devnode(struct device *dev, umode_t *mode)
 {
 	return kasprintf(GFP_KERNEL, "cpu/%u/cpuid", MINOR(dev->devt));
@@ -177,24 +154,17 @@ static int __init cpuid_init(void)
 	}
 	cpuid_class->devnode = cpuid_devnode;
 
-	cpu_notifier_register_begin();
-	for_each_online_cpu(i) {
-		err = cpuid_device_create(i);
-		if (err != 0)
-			goto out_class;
-	}
-	__register_hotcpu_notifier(&cpuid_class_cpu_notifier);
-	cpu_notifier_register_done();
+	err = cpuhp_setup_state(CPUHP_X86_CPUID_PREPARE, "x86/cpuid:prepare",
+				cpuid_device_create, cpuid_device_destroy);
+	if (err)
+		goto out_class;
 
 	err = 0;
 	goto out;
 
 out_class:
 	i = 0;
-	for_each_online_cpu(i) {
-		cpuid_device_destroy(i);
-	}
-	cpu_notifier_register_done();
+	cpuhp_remove_state(CPUHP_X86_CPUID_PREPARE);
 	class_destroy(cpuid_class);
 out_chrdev:
 	__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
@@ -204,15 +174,9 @@ static int __init cpuid_init(void)
 
 static void __exit cpuid_exit(void)
 {
-	int cpu = 0;
-
-	cpu_notifier_register_begin();
-	for_each_online_cpu(cpu)
-		cpuid_device_destroy(cpu);
+	cpuhp_remove_state(CPUHP_X86_CPUID_PREPARE);
 	class_destroy(cpuid_class);
 	__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
-	__unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
-	cpu_notifier_register_done();
 }
 
 module_init(cpuid_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index aea6c6a63139..2f9e083791c4 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -60,6 +60,7 @@ enum cpuhp_state {
 	CPUHP_NET_FLOW_PREPARE,
 	CPUHP_TOPOLOGY_PREPARE,
 	CPUHP_X86_THERM_PREPARE,
+	CPUHP_X86_CPUID_PREPARE,
 	CPUHP_TIMERS_DEAD,
 	CPUHP_NOTF_ERR_INJ_PREPARE,
 	CPUHP_MIPS_SOC_PREPARE,
-- 
2.10.2