2 * CPU subsystem support
5 #include <linux/kernel.h>
6 #include <linux/module.h>
7 #include <linux/init.h>
8 #include <linux/sched.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>
19 struct bus_type cpu_subsys = {
23 EXPORT_SYMBOL_GPL(cpu_subsys);
25 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
27 #ifdef CONFIG_HOTPLUG_CPU
28 static void change_cpu_under_node(struct cpu *cpu,
29 unsigned int from_nid, unsigned int to_nid)
31 int cpuid = cpu->dev.id;
32 unregister_cpu_under_node(cpuid, from_nid);
33 register_cpu_under_node(cpuid, to_nid);
34 cpu->node_id = to_nid;
37 static ssize_t show_online(struct device *dev,
38 struct device_attribute *attr,
41 struct cpu *cpu = container_of(dev, struct cpu, dev);
43 return sprintf(buf, "%u\n", !!cpu_online(cpu->dev.id));
46 static ssize_t __ref store_online(struct device *dev,
47 struct device_attribute *attr,
48 const char *buf, size_t count)
50 struct cpu *cpu = container_of(dev, struct cpu, dev);
51 int cpuid = cpu->dev.id;
55 cpu_hotplug_driver_lock();
58 ret = cpu_down(cpuid);
60 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
63 from_nid = cpu_to_node(cpuid);
67 * When hot adding memory to memoryless node and enabling a cpu
68 * on the node, node number of the cpu may internally change.
70 to_nid = cpu_to_node(cpuid);
71 if (from_nid != to_nid)
72 change_cpu_under_node(cpu, from_nid, to_nid);
75 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
80 cpu_hotplug_driver_unlock();
86 static DEVICE_ATTR(online, 0644, show_online, store_online);
88 static void __cpuinit register_cpu_control(struct cpu *cpu)
90 device_create_file(&cpu->dev, &dev_attr_online);
92 void unregister_cpu(struct cpu *cpu)
94 int logical_cpu = cpu->dev.id;
96 unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
98 device_remove_file(&cpu->dev, &dev_attr_online);
100 device_unregister(&cpu->dev);
101 per_cpu(cpu_sys_devices, logical_cpu) = NULL;
105 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
106 static ssize_t cpu_probe_store(struct device *dev,
107 struct device_attribute *attr,
111 return arch_cpu_probe(buf, count);
114 static ssize_t cpu_release_store(struct device *dev,
115 struct device_attribute *attr,
119 return arch_cpu_release(buf, count);
122 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
123 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
124 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
126 #else /* ... !CONFIG_HOTPLUG_CPU */
127 static inline void register_cpu_control(struct cpu *cpu)
130 #endif /* CONFIG_HOTPLUG_CPU */
133 #include <linux/kexec.h>
135 static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
138 struct cpu *cpu = container_of(dev, struct cpu, dev);
140 unsigned long long addr;
143 cpunum = cpu->dev.id;
146 * Might be reading other cpu's data based on which cpu read thread
147 * has been scheduled. But cpu data (memory) is allocated once during
148 * boot up and this data does not change there after. Hence this
149 * operation should be safe. No locking required.
151 addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
152 rc = sprintf(buf, "%Lx\n", addr);
155 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
157 static ssize_t show_crash_notes_size(struct device *dev,
158 struct device_attribute *attr,
163 rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
166 static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
170 * Print cpu online, possible, present, and system maps
174 struct device_attribute attr;
175 const struct cpumask *const * const map;
178 static ssize_t show_cpus_attr(struct device *dev,
179 struct device_attribute *attr,
182 struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
183 int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
190 #define _CPU_ATTR(name, map) \
191 { __ATTR(name, 0444, show_cpus_attr, NULL), map }
193 /* Keep in sync with cpu_subsys_attrs */
194 static struct cpu_attr cpu_attrs[] = {
195 _CPU_ATTR(online, &cpu_online_mask),
196 _CPU_ATTR(possible, &cpu_possible_mask),
197 _CPU_ATTR(present, &cpu_present_mask),
201 * Print values for NR_CPUS and offlined cpus
203 static ssize_t print_cpus_kernel_max(struct device *dev,
204 struct device_attribute *attr, char *buf)
206 int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
209 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
211 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
212 unsigned int total_cpus;
214 static ssize_t print_cpus_offline(struct device *dev,
215 struct device_attribute *attr, char *buf)
217 int n = 0, len = PAGE_SIZE-2;
218 cpumask_var_t offline;
220 /* display offline cpus < nr_cpu_ids */
221 if (!alloc_cpumask_var(&offline, GFP_KERNEL))
223 cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
224 n = cpulist_scnprintf(buf, len, offline);
225 free_cpumask_var(offline);
227 /* display offline cpus >= nr_cpu_ids */
228 if (total_cpus && nr_cpu_ids < total_cpus) {
232 if (nr_cpu_ids == total_cpus-1)
233 n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
235 n += snprintf(&buf[n], len - n, "%d-%d",
236 nr_cpu_ids, total_cpus-1);
239 n += snprintf(&buf[n], len - n, "\n");
242 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
244 static void cpu_device_release(struct device *dev)
247 * This is an empty function to prevent the driver core from spitting a
248 * warning at us. Yes, I know this is directly opposite of what the
249 * documentation for the driver core and kobjects say, and the author
250 * of this code has already been publically ridiculed for doing
251 * something as foolish as this. However, at this point in time, it is
252 * the only way to handle the issue of statically allocated cpu
253 * devices. The different architectures will have their cpu device
254 * code reworked to properly handle this in the near future, so this
255 * function will then be changed to correctly free up the memory held
258 * Never copy this way of doing things, or you too will be made fun of
259 * on the linux-kernel list, you have been warned.
264 * register_cpu - Setup a sysfs device for a CPU.
265 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
266 * sysfs for this CPU.
267 * @num - CPU number to use when creating the device.
269 * Initialize and register the CPU device.
271 int __cpuinit register_cpu(struct cpu *cpu, int num)
275 cpu->node_id = cpu_to_node(num);
276 memset(&cpu->dev, 0x00, sizeof(struct device));
278 cpu->dev.bus = &cpu_subsys;
279 cpu->dev.release = cpu_device_release;
280 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
281 cpu->dev.bus->uevent = arch_cpu_uevent;
283 error = device_register(&cpu->dev);
284 if (!error && cpu->hotpluggable)
285 register_cpu_control(cpu);
287 per_cpu(cpu_sys_devices, num) = &cpu->dev;
289 register_cpu_under_node(num, cpu_to_node(num));
293 error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
295 error = device_create_file(&cpu->dev,
296 &dev_attr_crash_notes_size);
301 struct device *get_cpu_device(unsigned cpu)
303 if (cpu < nr_cpu_ids && cpu_possible(cpu))
304 return per_cpu(cpu_sys_devices, cpu);
308 EXPORT_SYMBOL_GPL(get_cpu_device);
310 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
311 static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
314 static struct attribute *cpu_root_attrs[] = {
315 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
316 &dev_attr_probe.attr,
317 &dev_attr_release.attr,
319 &cpu_attrs[0].attr.attr,
320 &cpu_attrs[1].attr.attr,
321 &cpu_attrs[2].attr.attr,
322 &dev_attr_kernel_max.attr,
323 &dev_attr_offline.attr,
324 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
325 &dev_attr_modalias.attr,
330 static struct attribute_group cpu_root_attr_group = {
331 .attrs = cpu_root_attrs,
334 static const struct attribute_group *cpu_root_attr_groups[] = {
335 &cpu_root_attr_group,
339 bool cpu_is_hotpluggable(unsigned cpu)
341 struct device *dev = get_cpu_device(cpu);
342 return dev && container_of(dev, struct cpu, dev)->hotpluggable;
344 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
346 #ifdef CONFIG_GENERIC_CPU_DEVICES
347 static DEFINE_PER_CPU(struct cpu, cpu_devices);
350 static void __init cpu_dev_register_generic(void)
352 #ifdef CONFIG_GENERIC_CPU_DEVICES
355 for_each_possible_cpu(i) {
356 if (register_cpu(&per_cpu(cpu_devices, i), i))
357 panic("Failed to register CPU device");
362 void __init cpu_dev_init(void)
364 if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
365 panic("Failed to register CPU subsystem");
367 cpu_dev_register_generic();