linux/drivers/base/cpu.c
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   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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