drivers/base/cpu.c - arm/linux - Git at Google

 /*
  * CPU subsystem support
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/cpu.h>
 #include <linux/topology.h>
 #include <linux/device.h>
 #include <linux/node.h>
 #include <linux/gfp.h>
 #include <linux/slab.h>
 #include <linux/percpu.h>
 #include <linux/acpi.h>
 #include <linux/of.h>
 #include <linux/cpufeature.h>

 #include "base.h"

 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);

 static int cpu_subsys_match(struct device *dev, struct device_driver *drv)
 {
 	/* ACPI style match is the only one that may succeed. */
 	if (acpi_driver_match_device(dev, drv))
 		return 1;

 	return 0;
 }

 #ifdef CONFIG_HOTPLUG_CPU
 static void change_cpu_under_node(struct cpu *cpu,
 			unsigned int from_nid, unsigned int to_nid)
 {
 	int cpuid = cpu->dev.id;
 	unregister_cpu_under_node(cpuid, from_nid);
 	register_cpu_under_node(cpuid, to_nid);
 	cpu->node_id = to_nid;
 }

 static int __ref cpu_subsys_online(struct device *dev)
 {
 	struct cpu *cpu = container_of(dev, struct cpu, dev);
 	int cpuid = dev->id;
 	int from_nid, to_nid;
 	int ret;

 	from_nid = cpu_to_node(cpuid);
 	if (from_nid == NUMA_NO_NODE)
 		return -ENODEV;

 	ret = cpu_up(cpuid);
 	/*
 	 * When hot adding memory to memoryless node and enabling a cpu
 	 * on the node, node number of the cpu may internally change.
 	 */
 	to_nid = cpu_to_node(cpuid);
 	if (from_nid != to_nid)
 		change_cpu_under_node(cpu, from_nid, to_nid);

 	return ret;
 }

 static int cpu_subsys_offline(struct device *dev)
 {
 	return cpu_down(dev->id);
 }

 void unregister_cpu(struct cpu *cpu)
 {
 	int logical_cpu = cpu->dev.id;

 	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));

 	device_unregister(&cpu->dev);
 	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
 	return;
 }

 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 static ssize_t cpu_probe_store(struct device *dev,
 			       struct device_attribute *attr,
 			       const char *buf,
 			       size_t count)
 {
 	ssize_t cnt;
 	int ret;

 	ret = lock_device_hotplug_sysfs();
 	if (ret)
 		return ret;

 	cnt = arch_cpu_probe(buf, count);

 	unlock_device_hotplug();
 	return cnt;
 }

 static ssize_t cpu_release_store(struct device *dev,
 				 struct device_attribute *attr,
 				 const char *buf,
 				 size_t count)
 {
 	ssize_t cnt;
 	int ret;

 	ret = lock_device_hotplug_sysfs();
 	if (ret)
 		return ret;

 	cnt = arch_cpu_release(buf, count);

 	unlock_device_hotplug();
 	return cnt;
 }

 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 #endif /* CONFIG_HOTPLUG_CPU */

 struct bus_type cpu_subsys = {
 	.name = "cpu",
 	.dev_name = "cpu",
 	.match = cpu_subsys_match,
 #ifdef CONFIG_HOTPLUG_CPU
 	.online = cpu_subsys_online,
 	.offline = cpu_subsys_offline,
 #endif
 };
 EXPORT_SYMBOL_GPL(cpu_subsys);

 #ifdef CONFIG_KEXEC
 #include <linux/kexec.h>

 static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
 				char *buf)
 {
 	struct cpu *cpu = container_of(dev, struct cpu, dev);
 	ssize_t rc;
 	unsigned long long addr;
 	int cpunum;

 	cpunum = cpu->dev.id;

 	/*
 	 * Might be reading other cpu's data based on which cpu read thread
 	 * has been scheduled. But cpu data (memory) is allocated once during
 	 * boot up and this data does not change there after. Hence this
 	 * operation should be safe. No locking required.
 	 */
 	addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
 	rc = sprintf(buf, "%Lx\n", addr);
 	return rc;
 }
 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);

 static ssize_t show_crash_notes_size(struct device *dev,
 				     struct device_attribute *attr,
 				     char *buf)
 {
 	ssize_t rc;

 	rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
 	return rc;
 }
 static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);

 static struct attribute *crash_note_cpu_attrs[] = {
 	&dev_attr_crash_notes.attr,
 	&dev_attr_crash_notes_size.attr,
 	NULL
 };

 static struct attribute_group crash_note_cpu_attr_group = {
 	.attrs = crash_note_cpu_attrs,
 };
 #endif

 static const struct attribute_group *common_cpu_attr_groups[] = {
 #ifdef CONFIG_KEXEC
 	&crash_note_cpu_attr_group,
 #endif
 	NULL
 };

 static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
 #ifdef CONFIG_KEXEC
 	&crash_note_cpu_attr_group,
 #endif
 	NULL
 };

 /*
  * Print cpu online, possible, present, and system maps
  */

 struct cpu_attr {
 	struct device_attribute attr;
 	const struct cpumask *const * const map;
 };

 static ssize_t show_cpus_attr(struct device *dev,
 			      struct device_attribute *attr,
 			      char *buf)
 {
 	struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 	int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));

 	buf[n++] = '\n';
 	buf[n] = '\0';
 	return n;
 }

 #define _CPU_ATTR(name, map) \
 	{ __ATTR(name, 0444, show_cpus_attr, NULL), map }

 /* Keep in sync with cpu_subsys_attrs */
 static struct cpu_attr cpu_attrs[] = {
 	_CPU_ATTR(online, &cpu_online_mask),
 	_CPU_ATTR(possible, &cpu_possible_mask),
 	_CPU_ATTR(present, &cpu_present_mask),
 };

 /*
  * Print values for NR_CPUS and offlined cpus
  */
 static ssize_t print_cpus_kernel_max(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
 	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 	return n;
 }
 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);

 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 unsigned int total_cpus;

 static ssize_t print_cpus_offline(struct device *dev,
 				  struct device_attribute *attr, char *buf)
 {
 	int n = 0, len = PAGE_SIZE-2;
 	cpumask_var_t offline;

 	/* display offline cpus < nr_cpu_ids */
 	if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 		return -ENOMEM;
 	cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 	n = cpulist_scnprintf(buf, len, offline);
 	free_cpumask_var(offline);

 	/* display offline cpus >= nr_cpu_ids */
 	if (total_cpus && nr_cpu_ids < total_cpus) {
 		if (n && n < len)
 			buf[n++] = ',';

 		if (nr_cpu_ids == total_cpus-1)
 			n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
 		else
 			n += snprintf(&buf[n], len - n, "%d-%d",
 						      nr_cpu_ids, total_cpus-1);
 	}

 	n += snprintf(&buf[n], len - n, "\n");
 	return n;
 }
 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);

 static void cpu_device_release(struct device *dev)
 {
 	/*
 	 * This is an empty function to prevent the driver core from spitting a
 	 * warning at us.  Yes, I know this is directly opposite of what the
 	 * documentation for the driver core and kobjects say, and the author
 	 * of this code has already been publically ridiculed for doing
 	 * something as foolish as this.  However, at this point in time, it is
 	 * the only way to handle the issue of statically allocated cpu
 	 * devices.  The different architectures will have their cpu device
 	 * code reworked to properly handle this in the near future, so this
 	 * function will then be changed to correctly free up the memory held
 	 * by the cpu device.
 	 *
 	 * Never copy this way of doing things, or you too will be made fun of
 	 * on the linux-kernel list, you have been warned.
 	 */
 }

 #ifdef CONFIG_HAVE_CPU_AUTOPROBE
 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 static ssize_t print_cpu_modalias(struct device *dev,
 				  struct device_attribute *attr,
 				  char *buf)
 {
 	ssize_t n;
 	u32 i;

 	n = sprintf(buf, "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
 		    CPU_FEATURE_TYPEVAL);

 	for (i = 0; i < MAX_CPU_FEATURES; i++)
 		if (cpu_have_feature(i)) {
 			if (PAGE_SIZE < n + sizeof(",XXXX\n")) {
 				WARN(1, "CPU features overflow page\n");
 				break;
 			}
 			n += sprintf(&buf[n], ",%04X", i);
 		}
 	buf[n++] = '\n';
 	return n;
 }
 #else
 #define print_cpu_modalias	arch_print_cpu_modalias
 #endif

 static int cpu_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
 	char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
 	if (buf) {
 		print_cpu_modalias(NULL, NULL, buf);
 		add_uevent_var(env, "MODALIAS=%s", buf);
 		kfree(buf);
 	}
 	return 0;
 }
 #endif

 /*
  * register_cpu - Setup a sysfs device for a CPU.
  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
  *	  sysfs for this CPU.
  * @num - CPU number to use when creating the device.
  *
  * Initialize and register the CPU device.
  */
 int register_cpu(struct cpu *cpu, int num)
 {
 	int error;

 	cpu->node_id = cpu_to_node(num);
 	memset(&cpu->dev, 0x00, sizeof(struct device));
 	cpu->dev.id = num;
 	cpu->dev.bus = &cpu_subsys;
 	cpu->dev.release = cpu_device_release;
 	cpu->dev.offline_disabled = !cpu->hotpluggable;
 	cpu->dev.offline = !cpu_online(num);
 	cpu->dev.of_node = of_get_cpu_node(num, NULL);
 #ifdef CONFIG_HAVE_CPU_AUTOPROBE
 	cpu->dev.bus->uevent = cpu_uevent;
 #endif
 	cpu->dev.groups = common_cpu_attr_groups;
 	if (cpu->hotpluggable)
 		cpu->dev.groups = hotplugable_cpu_attr_groups;
 	error = device_register(&cpu->dev);
 	if (!error)
 		per_cpu(cpu_sys_devices, num) = &cpu->dev;
 	if (!error)
 		register_cpu_under_node(num, cpu_to_node(num));

 	return error;
 }

 struct device *get_cpu_device(unsigned cpu)
 {
 	if (cpu < nr_cpu_ids && cpu_possible(cpu))
 		return per_cpu(cpu_sys_devices, cpu);
 	else
 		return NULL;
 }
 EXPORT_SYMBOL_GPL(get_cpu_device);

 #ifdef CONFIG_HAVE_CPU_AUTOPROBE
 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
 #endif

 static struct attribute *cpu_root_attrs[] = {
 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 	&dev_attr_probe.attr,
 	&dev_attr_release.attr,
 #endif
 	&cpu_attrs[0].attr.attr,
 	&cpu_attrs[1].attr.attr,
 	&cpu_attrs[2].attr.attr,
 	&dev_attr_kernel_max.attr,
 	&dev_attr_offline.attr,
 #ifdef CONFIG_HAVE_CPU_AUTOPROBE
 	&dev_attr_modalias.attr,
 #endif
 	NULL
 };

 static struct attribute_group cpu_root_attr_group = {
 	.attrs = cpu_root_attrs,
 };

 static const struct attribute_group *cpu_root_attr_groups[] = {
 	&cpu_root_attr_group,
 	NULL,
 };

 bool cpu_is_hotpluggable(unsigned cpu)
 {
 	struct device *dev = get_cpu_device(cpu);
 	return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 }
 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);

 #ifdef CONFIG_GENERIC_CPU_DEVICES
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 #endif

 static void __init cpu_dev_register_generic(void)
 {
 #ifdef CONFIG_GENERIC_CPU_DEVICES
 	int i;

 	for_each_possible_cpu(i) {
 		if (register_cpu(&per_cpu(cpu_devices, i), i))
 			panic("Failed to register CPU device");
 	}
 #endif
 }

 void __init cpu_dev_init(void)
 {
 	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 		panic("Failed to register CPU subsystem");

 	cpu_dev_register_generic();
 }
	/*
	* CPU subsystem support
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/sched.h>
	#include <linux/cpu.h>
	#include <linux/topology.h>
	#include <linux/device.h>
	#include <linux/node.h>
	#include <linux/gfp.h>
	#include <linux/slab.h>
	#include <linux/percpu.h>
	#include <linux/acpi.h>
	#include <linux/of.h>
	#include <linux/cpufeature.h>

	#include "base.h"

	static DEFINE_PER_CPU(struct device *, cpu_sys_devices);

	static int cpu_subsys_match(struct device dev, struct device_driver drv)
	{
	/* ACPI style match is the only one that may succeed. */
	if (acpi_driver_match_device(dev, drv))
	return 1;

	return 0;
	}

	#ifdef CONFIG_HOTPLUG_CPU
	static void change_cpu_under_node(struct cpu *cpu,
	unsigned int from_nid, unsigned int to_nid)
	{
	int cpuid = cpu->dev.id;
	unregister_cpu_under_node(cpuid, from_nid);
	register_cpu_under_node(cpuid, to_nid);
	cpu->node_id = to_nid;
	}

	static int __ref cpu_subsys_online(struct device *dev)
	{
	struct cpu *cpu = container_of(dev, struct cpu, dev);
	int cpuid = dev->id;
	int from_nid, to_nid;
	int ret;

	from_nid = cpu_to_node(cpuid);
	if (from_nid == NUMA_NO_NODE)
	return -ENODEV;

	ret = cpu_up(cpuid);
	/*
	* When hot adding memory to memoryless node and enabling a cpu
	* on the node, node number of the cpu may internally change.
	*/
	to_nid = cpu_to_node(cpuid);
	if (from_nid != to_nid)
	change_cpu_under_node(cpu, from_nid, to_nid);

	return ret;
	}

	static int cpu_subsys_offline(struct device *dev)
	{
	return cpu_down(dev->id);
	}

	void unregister_cpu(struct cpu *cpu)
	{
	int logical_cpu = cpu->dev.id;

	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));

	device_unregister(&cpu->dev);
	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
	return;
	}

	#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
	static ssize_t cpu_probe_store(struct device *dev,
	struct device_attribute *attr,
	const char *buf,
	size_t count)
	{
	ssize_t cnt;
	int ret;

	ret = lock_device_hotplug_sysfs();
	if (ret)
	return ret;

	cnt = arch_cpu_probe(buf, count);

	unlock_device_hotplug();
	return cnt;
	}

	static ssize_t cpu_release_store(struct device *dev,
	struct device_attribute *attr,
	const char *buf,
	size_t count)
	{
	ssize_t cnt;
	int ret;

	ret = lock_device_hotplug_sysfs();
	if (ret)
	return ret;

	cnt = arch_cpu_release(buf, count);

	unlock_device_hotplug();
	return cnt;
	}

	static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
	static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
	#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
	#endif /* CONFIG_HOTPLUG_CPU */

	struct bus_type cpu_subsys = {
	.name = "cpu",
	.dev_name = "cpu",
	.match = cpu_subsys_match,
	#ifdef CONFIG_HOTPLUG_CPU
	.online = cpu_subsys_online,
	.offline = cpu_subsys_offline,
	#endif
	};
	EXPORT_SYMBOL_GPL(cpu_subsys);

	#ifdef CONFIG_KEXEC
	#include <linux/kexec.h>

	static ssize_t show_crash_notes(struct device dev, struct device_attribute attr,
	char *buf)
	{
	struct cpu *cpu = container_of(dev, struct cpu, dev);
	ssize_t rc;
	unsigned long long addr;
	int cpunum;

	cpunum = cpu->dev.id;

	/*
	* Might be reading other cpu's data based on which cpu read thread
	* has been scheduled. But cpu data (memory) is allocated once during
	* boot up and this data does not change there after. Hence this
	* operation should be safe. No locking required.
	*/
	addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
	rc = sprintf(buf, "%Lx\n", addr);
	return rc;
	}
	static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);

	static ssize_t show_crash_notes_size(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	ssize_t rc;

	rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
	return rc;
	}
	static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);

	static struct attribute *crash_note_cpu_attrs[] = {
	&dev_attr_crash_notes.attr,
	&dev_attr_crash_notes_size.attr,
	NULL
	};

	static struct attribute_group crash_note_cpu_attr_group = {
	.attrs = crash_note_cpu_attrs,
	};
	#endif

	static const struct attribute_group *common_cpu_attr_groups[] = {
	#ifdef CONFIG_KEXEC
	&crash_note_cpu_attr_group,
	#endif
	NULL
	};

	static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
	#ifdef CONFIG_KEXEC
	&crash_note_cpu_attr_group,
	#endif
	NULL
	};

	/*
	* Print cpu online, possible, present, and system maps
	*/

	struct cpu_attr {
	struct device_attribute attr;
	const struct cpumask const const map;
	};

	static ssize_t show_cpus_attr(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
	int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));

	buf[n++] = '\n';
	buf[n] = '\0';
	return n;
	}

	#define _CPU_ATTR(name, map) \
	{ __ATTR(name, 0444, show_cpus_attr, NULL), map }

	/* Keep in sync with cpu_subsys_attrs */
	static struct cpu_attr cpu_attrs[] = {
	_CPU_ATTR(online, &cpu_online_mask),
	_CPU_ATTR(possible, &cpu_possible_mask),
	_CPU_ATTR(present, &cpu_present_mask),
	};

	/*
	* Print values for NR_CPUS and offlined cpus
	*/
	static ssize_t print_cpus_kernel_max(struct device *dev,
	struct device_attribute attr, char buf)
	{
	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
	return n;
	}
	static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);

	/* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
	unsigned int total_cpus;

	static ssize_t print_cpus_offline(struct device *dev,
	struct device_attribute attr, char buf)
	{
	int n = 0, len = PAGE_SIZE-2;
	cpumask_var_t offline;

	/* display offline cpus < nr_cpu_ids */
	if (!alloc_cpumask_var(&offline, GFP_KERNEL))
	return -ENOMEM;
	cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
	n = cpulist_scnprintf(buf, len, offline);
	free_cpumask_var(offline);

	/* display offline cpus >= nr_cpu_ids */
	if (total_cpus && nr_cpu_ids < total_cpus) {
	if (n && n < len)
	buf[n++] = ',';

	if (nr_cpu_ids == total_cpus-1)
	n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
	else
	n += snprintf(&buf[n], len - n, "%d-%d",
	nr_cpu_ids, total_cpus-1);
	}

	n += snprintf(&buf[n], len - n, "\n");
	return n;
	}
	static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);

	static void cpu_device_release(struct device *dev)
	{
	/*
	* This is an empty function to prevent the driver core from spitting a
	* warning at us. Yes, I know this is directly opposite of what the
	* documentation for the driver core and kobjects say, and the author
	* of this code has already been publically ridiculed for doing
	* something as foolish as this. However, at this point in time, it is
	* the only way to handle the issue of statically allocated cpu
	* devices. The different architectures will have their cpu device
	* code reworked to properly handle this in the near future, so this
	* function will then be changed to correctly free up the memory held
	* by the cpu device.
	*
	* Never copy this way of doing things, or you too will be made fun of
	* on the linux-kernel list, you have been warned.
	*/
	}

	#ifdef CONFIG_HAVE_CPU_AUTOPROBE
	#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
	static ssize_t print_cpu_modalias(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	ssize_t n;
	u32 i;

	n = sprintf(buf, "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
	CPU_FEATURE_TYPEVAL);

	for (i = 0; i < MAX_CPU_FEATURES; i++)
	if (cpu_have_feature(i)) {
	if (PAGE_SIZE < n + sizeof(",XXXX\n")) {
	WARN(1, "CPU features overflow page\n");
	break;
	}
	n += sprintf(&buf[n], ",%04X", i);
	}
	buf[n++] = '\n';
	return n;
	}
	#else
	#define print_cpu_modalias arch_print_cpu_modalias
	#endif

	static int cpu_uevent(struct device dev, struct kobj_uevent_env env)
	{
	char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (buf) {
	print_cpu_modalias(NULL, NULL, buf);
	add_uevent_var(env, "MODALIAS=%s", buf);
	kfree(buf);
	}
	return 0;
	}
	#endif

	/*
	* register_cpu - Setup a sysfs device for a CPU.
	* @cpu - cpu->hotpluggable field set to 1 will generate a control file in
	* sysfs for this CPU.
	* @num - CPU number to use when creating the device.
	*
	* Initialize and register the CPU device.
	*/
	int register_cpu(struct cpu *cpu, int num)
	{
	int error;

	cpu->node_id = cpu_to_node(num);
	memset(&cpu->dev, 0x00, sizeof(struct device));
	cpu->dev.id = num;
	cpu->dev.bus = &cpu_subsys;
	cpu->dev.release = cpu_device_release;
	cpu->dev.offline_disabled = !cpu->hotpluggable;
	cpu->dev.offline = !cpu_online(num);
	cpu->dev.of_node = of_get_cpu_node(num, NULL);
	#ifdef CONFIG_HAVE_CPU_AUTOPROBE
	cpu->dev.bus->uevent = cpu_uevent;
	#endif
	cpu->dev.groups = common_cpu_attr_groups;
	if (cpu->hotpluggable)
	cpu->dev.groups = hotplugable_cpu_attr_groups;
	error = device_register(&cpu->dev);
	if (!error)
	per_cpu(cpu_sys_devices, num) = &cpu->dev;
	if (!error)
	register_cpu_under_node(num, cpu_to_node(num));

	return error;
	}

	struct device *get_cpu_device(unsigned cpu)
	{
	if (cpu < nr_cpu_ids && cpu_possible(cpu))
	return per_cpu(cpu_sys_devices, cpu);
	else
	return NULL;
	}
	EXPORT_SYMBOL_GPL(get_cpu_device);

	#ifdef CONFIG_HAVE_CPU_AUTOPROBE
	static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
	#endif

	static struct attribute *cpu_root_attrs[] = {
	#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
	&dev_attr_probe.attr,
	&dev_attr_release.attr,
	#endif
	&cpu_attrs[0].attr.attr,
	&cpu_attrs[1].attr.attr,
	&cpu_attrs[2].attr.attr,
	&dev_attr_kernel_max.attr,
	&dev_attr_offline.attr,
	#ifdef CONFIG_HAVE_CPU_AUTOPROBE
	&dev_attr_modalias.attr,
	#endif
	NULL
	};

	static struct attribute_group cpu_root_attr_group = {
	.attrs = cpu_root_attrs,
	};

	static const struct attribute_group *cpu_root_attr_groups[] = {
	&cpu_root_attr_group,
	NULL,
	};

	bool cpu_is_hotpluggable(unsigned cpu)
	{
	struct device *dev = get_cpu_device(cpu);
	return dev && container_of(dev, struct cpu, dev)->hotpluggable;
	}
	EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);

	#ifdef CONFIG_GENERIC_CPU_DEVICES
	static DEFINE_PER_CPU(struct cpu, cpu_devices);
	#endif

	static void __init cpu_dev_register_generic(void)
	{
	#ifdef CONFIG_GENERIC_CPU_DEVICES
	int i;

	for_each_possible_cpu(i) {
	if (register_cpu(&per_cpu(cpu_devices, i), i))
	panic("Failed to register CPU device");
	}
	#endif
	}

	void __init cpu_dev_init(void)
	{
	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
	panic("Failed to register CPU subsystem");

	cpu_dev_register_generic();
	}