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/percpu.h>
  15
  16 #include "base.h"
  17
  18 struct bus_type cpu_subsys = {
  19         .name = "cpu",
  20         .dev_name = "cpu",
  21 };
  22 EXPORT_SYMBOL_GPL(cpu_subsys);
  23
  24 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
  25
  26 #ifdef CONFIG_HOTPLUG_CPU
  27 static 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
  36 static 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 }
  64 static DEVICE_ATTR(online, 0644, show_online, store_online);
  65
  66 static void __cpuinit register_cpu_control(struct cpu *cpu)
  67 {
  68         device_create_file(&cpu->dev, &dev_attr_online);
  69 }
  70 void 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
  84 static 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
  92 static 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
 100 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 101 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 102 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 103
 104 #else /* ... !CONFIG_HOTPLUG_CPU */
 105 static 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
 113 static 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 }
 133 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 134 #endif
 135
 136 /*
 137  * Print cpu online, possible, present, and system maps
 138  */
 139
 140 struct cpu_attr {
 141         struct device_attribute attr;
 142         const struct cpumask *const * const map;
 143 };
 144
 145 static 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 */
 161 static 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  */
 170 static 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 }
 176 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 177
 178 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 179 unsigned int total_cpus;
 180
 181 static 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 }
 209 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 210
 211 static void cpu_device_release(struct device *dev)
 212 {
 213         /*
 214          * This is an empty function to prevent the driver core from spitting a
 215          * warning at us.  Yes, I know this is directly opposite of what the
 216          * documentation for the driver core and kobjects say, and the author
 217          * of this code has already been publically ridiculed for doing
 218          * something as foolish as this.  However, at this point in time, it is
 219          * the only way to handle the issue of statically allocated cpu
 220          * devices.  The different architectures will have their cpu device
 221          * code reworked to properly handle this in the near future, so this
 222          * function will then be changed to correctly free up the memory held
 223          * by the cpu device.
 224          *
 225          * Never copy this way of doing things, or you too will be made fun of
 226          * on the linux-kerenl list, you have been warned.
 227          */
 228 }
 229
 230 /*
 231  * register_cpu - Setup a sysfs device for a CPU.
 232  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 233  *        sysfs for this CPU.
 234  * @num - CPU number to use when creating the device.
 235  *
 236  * Initialize and register the CPU device.
 237  */
 238 int __cpuinit register_cpu(struct cpu *cpu, int num)
 239 {
 240         int error;
 241
 242         cpu->node_id = cpu_to_node(num);
 243         memset(&cpu->dev, 0x00, sizeof(struct device));
 244         cpu->dev.id = num;
 245         cpu->dev.bus = &cpu_subsys;
 246         cpu->dev.release = cpu_device_release;
 247         error = device_register(&cpu->dev);
 248         if (!error && cpu->hotpluggable)
 249                 register_cpu_control(cpu);
 250         if (!error)
 251                 per_cpu(cpu_sys_devices, num) = &cpu->dev;
 252         if (!error)
 253                 register_cpu_under_node(num, cpu_to_node(num));
 254
 255 #ifdef CONFIG_KEXEC
 256         if (!error)
 257                 error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
 258 #endif
 259         return error;
 260 }
 261
 262 struct device *get_cpu_device(unsigned cpu)
 263 {
 264         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 265                 return per_cpu(cpu_sys_devices, cpu);
 266         else
 267                 return NULL;
 268 }
 269 EXPORT_SYMBOL_GPL(get_cpu_device);
 270
 271 static struct attribute *cpu_root_attrs[] = {
 272 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 273         &dev_attr_probe.attr,
 274         &dev_attr_release.attr,
 275 #endif
 276         &cpu_attrs[0].attr.attr,
 277         &cpu_attrs[1].attr.attr,
 278         &cpu_attrs[2].attr.attr,
 279         &dev_attr_kernel_max.attr,
 280         &dev_attr_offline.attr,
 281         NULL
 282 };
 283
 284 static struct attribute_group cpu_root_attr_group = {
 285         .attrs = cpu_root_attrs,
 286 };
 287
 288 static const struct attribute_group *cpu_root_attr_groups[] = {
 289         &cpu_root_attr_group,
 290         NULL,
 291 };
 292
 293 bool cpu_is_hotpluggable(unsigned cpu)
 294 {
 295         struct device *dev = get_cpu_device(cpu);
 296         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 297 }
 298 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 299
 300 #ifdef CONFIG_GENERIC_CPU_DEVICES
 301 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 302 #endif
 303
 304 static void __init cpu_dev_register_generic(void)
 305 {
 306 #ifdef CONFIG_GENERIC_CPU_DEVICES
 307         int i;
 308
 309         for_each_possible_cpu(i) {
 310                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 311                         panic("Failed to register CPU device");
 312         }
 313 #endif
 314 }
 315
 316 void __init cpu_dev_init(void)
 317 {
 318         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 319                 panic("Failed to register CPU subsystem");
 320
 321         cpu_dev_register_generic();
 322
 323 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
 324         sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
 325 #endif
 326 }