Root/drivers/base/cpu.c

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
212static void cpu_device_release(struct device *dev)
213{
214    /*
215     * This is an empty function to prevent the driver core from spitting a
216     * warning at us. Yes, I know this is directly opposite of what the
217     * documentation for the driver core and kobjects say, and the author
218     * of this code has already been publically ridiculed for doing
219     * something as foolish as this. However, at this point in time, it is
220     * the only way to handle the issue of statically allocated cpu
221     * devices. The different architectures will have their cpu device
222     * code reworked to properly handle this in the near future, so this
223     * function will then be changed to correctly free up the memory held
224     * by the cpu device.
225     *
226     * Never copy this way of doing things, or you too will be made fun of
227     * on the linux-kernel list, you have been warned.
228     */
229}
230
231/*
232 * register_cpu - Setup a sysfs device for a CPU.
233 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
234 * sysfs for this CPU.
235 * @num - CPU number to use when creating the device.
236 *
237 * Initialize and register the CPU device.
238 */
239int __cpuinit register_cpu(struct cpu *cpu, int num)
240{
241    int error;
242
243    cpu->node_id = cpu_to_node(num);
244    memset(&cpu->dev, 0x00, sizeof(struct device));
245    cpu->dev.id = num;
246    cpu->dev.bus = &cpu_subsys;
247    cpu->dev.release = cpu_device_release;
248#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
249    cpu->dev.bus->uevent = arch_cpu_uevent;
250#endif
251    error = device_register(&cpu->dev);
252    if (!error && cpu->hotpluggable)
253        register_cpu_control(cpu);
254    if (!error)
255        per_cpu(cpu_sys_devices, num) = &cpu->dev;
256    if (!error)
257        register_cpu_under_node(num, cpu_to_node(num));
258
259#ifdef CONFIG_KEXEC
260    if (!error)
261        error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
262#endif
263    return error;
264}
265
266struct device *get_cpu_device(unsigned cpu)
267{
268    if (cpu < nr_cpu_ids && cpu_possible(cpu))
269        return per_cpu(cpu_sys_devices, cpu);
270    else
271        return NULL;
272}
273EXPORT_SYMBOL_GPL(get_cpu_device);
274
275#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
276static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
277#endif
278
279static struct attribute *cpu_root_attrs[] = {
280#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
281    &dev_attr_probe.attr,
282    &dev_attr_release.attr,
283#endif
284    &cpu_attrs[0].attr.attr,
285    &cpu_attrs[1].attr.attr,
286    &cpu_attrs[2].attr.attr,
287    &dev_attr_kernel_max.attr,
288    &dev_attr_offline.attr,
289#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
290    &dev_attr_modalias.attr,
291#endif
292    NULL
293};
294
295static struct attribute_group cpu_root_attr_group = {
296    .attrs = cpu_root_attrs,
297};
298
299static const struct attribute_group *cpu_root_attr_groups[] = {
300    &cpu_root_attr_group,
301    NULL,
302};
303
304bool cpu_is_hotpluggable(unsigned cpu)
305{
306    struct device *dev = get_cpu_device(cpu);
307    return dev && container_of(dev, struct cpu, dev)->hotpluggable;
308}
309EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
310
311#ifdef CONFIG_GENERIC_CPU_DEVICES
312static DEFINE_PER_CPU(struct cpu, cpu_devices);
313#endif
314
315static void __init cpu_dev_register_generic(void)
316{
317#ifdef CONFIG_GENERIC_CPU_DEVICES
318    int i;
319
320    for_each_possible_cpu(i) {
321        if (register_cpu(&per_cpu(cpu_devices, i), i))
322            panic("Failed to register CPU device");
323    }
324#endif
325}
326
327void __init cpu_dev_init(void)
328{
329    if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
330        panic("Failed to register CPU subsystem");
331
332    cpu_dev_register_generic();
333}
334

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