cpu.c revision fad12ac8c8c2591c7f4e61d19b6a9d76cd49fafa 
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/slab.h>
15#include <linux/percpu.h>
16
17#include "base.h"
18
19struct bus_type cpu_subsys = {
20	.name = "cpu",
21	.dev_name = "cpu",
22};
23EXPORT_SYMBOL_GPL(cpu_subsys);
24
25static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
26
27#ifdef CONFIG_HOTPLUG_CPU
28static ssize_t show_online(struct device *dev,
29			   struct device_attribute *attr,
30			   char *buf)
31{
32	struct cpu *cpu = container_of(dev, struct cpu, dev);
33
34	return sprintf(buf, "%u\n", !!cpu_online(cpu->dev.id));
35}
36
37static ssize_t __ref store_online(struct device *dev,
38				  struct device_attribute *attr,
39				  const char *buf, size_t count)
40{
41	struct cpu *cpu = container_of(dev, struct cpu, dev);
42	ssize_t ret;
43
44	cpu_hotplug_driver_lock();
45	switch (buf[0]) {
46	case '0':
47		ret = cpu_down(cpu->dev.id);
48		if (!ret)
49			kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
50		break;
51	case '1':
52		ret = cpu_up(cpu->dev.id);
53		if (!ret)
54			kobject_uevent(&dev->kobj, KOBJ_ONLINE);
55		break;
56	default:
57		ret = -EINVAL;
58	}
59	cpu_hotplug_driver_unlock();
60
61	if (ret >= 0)
62		ret = count;
63	return ret;
64}
65static DEVICE_ATTR(online, 0644, show_online, store_online);
66
67static void __cpuinit register_cpu_control(struct cpu *cpu)
68{
69	device_create_file(&cpu->dev, &dev_attr_online);
70}
71void unregister_cpu(struct cpu *cpu)
72{
73	int logical_cpu = cpu->dev.id;
74
75	unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
76
77	device_remove_file(&cpu->dev, &dev_attr_online);
78
79	device_unregister(&cpu->dev);
80	per_cpu(cpu_sys_devices, logical_cpu) = NULL;
81	return;
82}
83
84#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
85static ssize_t cpu_probe_store(struct device *dev,
86			       struct device_attribute *attr,
87			       const char *buf,
88			       size_t count)
89{
90	return arch_cpu_probe(buf, count);
91}
92
93static ssize_t cpu_release_store(struct device *dev,
94				 struct device_attribute *attr,
95				 const char *buf,
96				 size_t count)
97{
98	return arch_cpu_release(buf, count);
99}
100
101static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
102static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
103#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
104
105#else /* ... !CONFIG_HOTPLUG_CPU */
106static inline void register_cpu_control(struct cpu *cpu)
107{
108}
109#endif /* CONFIG_HOTPLUG_CPU */
110
111#ifdef CONFIG_KEXEC
112#include <linux/kexec.h>
113
114static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
115				char *buf)
116{
117	struct cpu *cpu = container_of(dev, struct cpu, dev);
118	ssize_t rc;
119	unsigned long long addr;
120	int cpunum;
121
122	cpunum = cpu->dev.id;
123
124	/*
125	 * Might be reading other cpu's data based on which cpu read thread
126	 * has been scheduled. But cpu data (memory) is allocated once during
127	 * boot up and this data does not change there after. Hence this
128	 * operation should be safe. No locking required.
129	 */
130	addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
131	rc = sprintf(buf, "%Lx\n", addr);
132	return rc;
133}
134static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
135#endif
136
137/*
138 * Print cpu online, possible, present, and system maps
139 */
140
141struct cpu_attr {
142	struct device_attribute attr;
143	const struct cpumask *const * const map;
144};
145
146static ssize_t show_cpus_attr(struct device *dev,
147			      struct device_attribute *attr,
148			      char *buf)
149{
150	struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
151	int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
152
153	buf[n++] = '\n';
154	buf[n] = '\0';
155	return n;
156}
157
158#define _CPU_ATTR(name, map) \
159	{ __ATTR(name, 0444, show_cpus_attr, NULL), map }
160
161/* Keep in sync with cpu_subsys_attrs */
162static struct cpu_attr cpu_attrs[] = {
163	_CPU_ATTR(online, &cpu_online_mask),
164	_CPU_ATTR(possible, &cpu_possible_mask),
165	_CPU_ATTR(present, &cpu_present_mask),
166};
167
168/*
169 * Print values for NR_CPUS and offlined cpus
170 */
171static ssize_t print_cpus_kernel_max(struct device *dev,
172				     struct device_attribute *attr, char *buf)
173{
174	int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
175	return n;
176}
177static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
178
179/* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
180unsigned int total_cpus;
181
182static ssize_t print_cpus_offline(struct device *dev,
183				  struct device_attribute *attr, char *buf)
184{
185	int n = 0, len = PAGE_SIZE-2;
186	cpumask_var_t offline;
187
188	/* display offline cpus < nr_cpu_ids */
189	if (!alloc_cpumask_var(&offline, GFP_KERNEL))
190		return -ENOMEM;
191	cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
192	n = cpulist_scnprintf(buf, len, offline);
193	free_cpumask_var(offline);
194
195	/* display offline cpus >= nr_cpu_ids */
196	if (total_cpus && nr_cpu_ids < total_cpus) {
197		if (n && n < len)
198			buf[n++] = ',';
199
200		if (nr_cpu_ids == total_cpus-1)
201			n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
202		else
203			n += snprintf(&buf[n], len - n, "%d-%d",
204						      nr_cpu_ids, total_cpus-1);
205	}
206
207	n += snprintf(&buf[n], len - n, "\n");
208	return n;
209}
210static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
211
212/*
213 * register_cpu - Setup a sysfs device for a CPU.
214 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
215 *	  sysfs for this CPU.
216 * @num - CPU number to use when creating the device.
217 *
218 * Initialize and register the CPU device.
219 */
220int __cpuinit register_cpu(struct cpu *cpu, int num)
221{
222	int error;
223
224	cpu->node_id = cpu_to_node(num);
225	cpu->dev.id = num;
226	cpu->dev.bus = &cpu_subsys;
227#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
228	cpu->dev.bus->uevent = arch_cpu_uevent;
229#endif
230	error = device_register(&cpu->dev);
231	if (!error && cpu->hotpluggable)
232		register_cpu_control(cpu);
233	if (!error)
234		per_cpu(cpu_sys_devices, num) = &cpu->dev;
235	if (!error)
236		register_cpu_under_node(num, cpu_to_node(num));
237
238#ifdef CONFIG_KEXEC
239	if (!error)
240		error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
241#endif
242	return error;
243}
244
245struct device *get_cpu_device(unsigned cpu)
246{
247	if (cpu < nr_cpu_ids && cpu_possible(cpu))
248		return per_cpu(cpu_sys_devices, cpu);
249	else
250		return NULL;
251}
252EXPORT_SYMBOL_GPL(get_cpu_device);
253
254#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
255static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
256#endif
257
258static struct attribute *cpu_root_attrs[] = {
259#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
260	&dev_attr_probe.attr,
261	&dev_attr_release.attr,
262#endif
263	&cpu_attrs[0].attr.attr,
264	&cpu_attrs[1].attr.attr,
265	&cpu_attrs[2].attr.attr,
266	&dev_attr_kernel_max.attr,
267	&dev_attr_offline.attr,
268#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
269	&dev_attr_modalias.attr,
270#endif
271	NULL
272};
273
274static struct attribute_group cpu_root_attr_group = {
275	.attrs = cpu_root_attrs,
276};
277
278static const struct attribute_group *cpu_root_attr_groups[] = {
279	&cpu_root_attr_group,
280	NULL,
281};
282
283bool cpu_is_hotpluggable(unsigned cpu)
284{
285	struct device *dev = get_cpu_device(cpu);
286	return dev && container_of(dev, struct cpu, dev)->hotpluggable;
287}
288EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
289
290#ifdef CONFIG_GENERIC_CPU_DEVICES
291static DEFINE_PER_CPU(struct cpu, cpu_devices);
292#endif
293
294static void __init cpu_dev_register_generic(void)
295{
296#ifdef CONFIG_GENERIC_CPU_DEVICES
297	int i;
298
299	for_each_possible_cpu(i) {
300		if (register_cpu(&per_cpu(cpu_devices, i), i))
301			panic("Failed to register CPU device");
302	}
303#endif
304}
305
306void __init cpu_dev_init(void)
307{
308	if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
309		panic("Failed to register CPU subsystem");
310
311	cpu_dev_register_generic();
312
313#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
314	sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
315#endif
316}
317