cpu.c revision 9f13a1fd452f11c18004ba2422a6384b424ec8a9 
1/*
2 * CPU subsystem support
3 */
4
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/init.h>
8#include <linux/sched.h>
9#include <linux/cpu.h>
10#include <linux/topology.h>
11#include <linux/device.h>
12#include <linux/node.h>
13#include <linux/gfp.h>
14#include <linux/percpu.h>
15
16#include "base.h"
17
18struct bus_type cpu_subsys = {
19	.name = "cpu",
20	.dev_name = "cpu",
21};
22EXPORT_SYMBOL_GPL(cpu_subsys);
23
24static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
25
26#ifdef CONFIG_HOTPLUG_CPU
27static ssize_t show_online(struct device *dev,
28			   struct device_attribute *attr,
29			   char *buf)
30{
31	struct cpu *cpu = container_of(dev, struct cpu, dev);
32
33	return sprintf(buf, "%u\n", !!cpu_online(cpu->dev.id));
34}
35
36static ssize_t __ref store_online(struct device *dev,
37				  struct device_attribute *attr,
38				  const char *buf, size_t count)
39{
40	struct cpu *cpu = container_of(dev, struct cpu, dev);
41	ssize_t ret;
42
43	cpu_hotplug_driver_lock();
44	switch (buf[0]) {
45	case '0':
46		ret = cpu_down(cpu->dev.id);
47		if (!ret)
48			kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
49		break;
50	case '1':
51		ret = cpu_up(cpu->dev.id);
52		if (!ret)
53			kobject_uevent(&dev->kobj, KOBJ_ONLINE);
54		break;
55	default:
56		ret = -EINVAL;
57	}
58	cpu_hotplug_driver_unlock();
59
60	if (ret >= 0)
61		ret = count;
62	return ret;
63}
64static DEVICE_ATTR(online, 0644, show_online, store_online);
65
66static void __cpuinit register_cpu_control(struct cpu *cpu)
67{
68	device_create_file(&cpu->dev, &dev_attr_online);
69}
70void unregister_cpu(struct cpu *cpu)
71{
72	int logical_cpu = cpu->dev.id;
73
74	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
75
76	device_remove_file(&cpu->dev, &dev_attr_online);
77
78	device_unregister(&cpu->dev);
79	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
80	return;
81}
82
83#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
84static ssize_t cpu_probe_store(struct device *dev,
85			       struct device_attribute *attr,
86			       const char *buf,
87			       size_t count)
88{
89	return arch_cpu_probe(buf, count);
90}
91
92static ssize_t cpu_release_store(struct device *dev,
93				 struct device_attribute *attr,
94				 const char *buf,
95				 size_t count)
96{
97	return arch_cpu_release(buf, count);
98}
99
100static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
101static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
102#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
103
104#else /* ... !CONFIG_HOTPLUG_CPU */
105static inline void register_cpu_control(struct cpu *cpu)
106{
107}
108#endif /* CONFIG_HOTPLUG_CPU */
109
110#ifdef CONFIG_KEXEC
111#include <linux/kexec.h>
112
113static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
114				char *buf)
115{
116	struct cpu *cpu = container_of(dev, struct cpu, dev);
117	ssize_t rc;
118	unsigned long long addr;
119	int cpunum;
120
121	cpunum = cpu->dev.id;
122
123	/*
124	 * Might be reading other cpu's data based on which cpu read thread
125	 * has been scheduled. But cpu data (memory) is allocated once during
126	 * boot up and this data does not change there after. Hence this
127	 * operation should be safe. No locking required.
128	 */
129	addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
130	rc = sprintf(buf, "%Lx\n", addr);
131	return rc;
132}
133static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
134#endif
135
136/*
137 * Print cpu online, possible, present, and system maps
138 */
139
140struct cpu_attr {
141	struct device_attribute attr;
142	const struct cpumask *const * const map;
143};
144
145static ssize_t show_cpus_attr(struct device *dev,
146			      struct device_attribute *attr,
147			      char *buf)
148{
149	struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
150	int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
151
152	buf[n++] = '\n';
153	buf[n] = '\0';
154	return n;
155}
156
157#define _CPU_ATTR(name, map) \
158	{ __ATTR(name, 0444, show_cpus_attr, NULL), map }
159
160/* Keep in sync with cpu_subsys_attrs */
161static struct cpu_attr cpu_attrs[] = {
162	_CPU_ATTR(online, &cpu_online_mask),
163	_CPU_ATTR(possible, &cpu_possible_mask),
164	_CPU_ATTR(present, &cpu_present_mask),
165};
166
167/*
168 * Print values for NR_CPUS and offlined cpus
169 */
170static ssize_t print_cpus_kernel_max(struct device *dev,
171				     struct device_attribute *attr, char *buf)
172{
173	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
174	return n;
175}
176static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
177
178/* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
179unsigned int total_cpus;
180
181static ssize_t print_cpus_offline(struct device *dev,
182				  struct device_attribute *attr, char *buf)
183{
184	int n = 0, len = PAGE_SIZE-2;
185	cpumask_var_t offline;
186
187	/* display offline cpus < nr_cpu_ids */
188	if (!alloc_cpumask_var(&offline, GFP_KERNEL))
189		return -ENOMEM;
190	cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
191	n = cpulist_scnprintf(buf, len, offline);
192	free_cpumask_var(offline);
193
194	/* display offline cpus >= nr_cpu_ids */
195	if (total_cpus && nr_cpu_ids < total_cpus) {
196		if (n && n < len)
197			buf[n++] = ',';
198
199		if (nr_cpu_ids == total_cpus-1)
200			n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
201		else
202			n += snprintf(&buf[n], len - n, "%d-%d",
203						      nr_cpu_ids, total_cpus-1);
204	}
205
206	n += snprintf(&buf[n], len - n, "\n");
207	return n;
208}
209static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
210
211/*
212 * register_cpu - Setup a sysfs device for a CPU.
213 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
214 *	  sysfs for this CPU.
215 * @num - CPU number to use when creating the device.
216 *
217 * Initialize and register the CPU device.
218 */
219int __cpuinit register_cpu(struct cpu *cpu, int num)
220{
221	int error;
222
223	cpu->node_id = cpu_to_node(num);
224	cpu->dev.id = num;
225	cpu->dev.bus = &cpu_subsys;
226	error = device_register(&cpu->dev);
227	if (!error && cpu->hotpluggable)
228		register_cpu_control(cpu);
229	if (!error)
230		per_cpu(cpu_sys_devices, num) = &cpu->dev;
231	if (!error)
232		register_cpu_under_node(num, cpu_to_node(num));
233
234#ifdef CONFIG_KEXEC
235	if (!error)
236		error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
237#endif
238	return error;
239}
240
241struct device *get_cpu_device(unsigned cpu)
242{
243	if (cpu < nr_cpu_ids && cpu_possible(cpu))
244		return per_cpu(cpu_sys_devices, cpu);
245	else
246		return NULL;
247}
248EXPORT_SYMBOL_GPL(get_cpu_device);
249
250static struct attribute *cpu_root_attrs[] = {
251#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
252	&dev_attr_probe.attr,
253	&dev_attr_release.attr,
254#endif
255	&cpu_attrs[0].attr.attr,
256	&cpu_attrs[1].attr.attr,
257	&cpu_attrs[2].attr.attr,
258	&dev_attr_kernel_max.attr,
259	&dev_attr_offline.attr,
260	NULL
261};
262
263static struct attribute_group cpu_root_attr_group = {
264	.attrs = cpu_root_attrs,
265};
266
267static const struct attribute_group *cpu_root_attr_groups[] = {
268	&cpu_root_attr_group,
269	NULL,
270};
271
272bool cpu_is_hotpluggable(unsigned cpu)
273{
274	struct device *dev = get_cpu_device(cpu);
275	return dev && container_of(dev, struct cpu, dev)->hotpluggable;
276}
277EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
278
279#ifdef CONFIG_GENERIC_CPU_DEVICES
280static DEFINE_PER_CPU(struct cpu, cpu_devices);
281#endif
282
283static void __init cpu_dev_register_generic(void)
284{
285#ifdef CONFIG_GENERIC_CPU_DEVICES
286	int i;
287
288	for_each_possible_cpu(i) {
289		if (register_cpu(&per_cpu(cpu_devices, i), i))
290			panic("Failed to register CPU device");
291	}
292#endif
293}
294
295void __init cpu_dev_init(void)
296{
297	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
298		panic("Failed to register CPU subsystem");
299
300	cpu_dev_register_generic();
301
302#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
303	sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
304#endif
305}
306