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
  19 struct bus_type cpu_subsys = {
  20         .name = "cpu",
  21         .dev_name = "cpu",
  22 };
  23 EXPORT_SYMBOL_GPL(cpu_subsys);
  24
  25 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
  26
  27 #ifdef CONFIG_HOTPLUG_CPU
  28 static void change_cpu_under_node(struct cpu *cpu,
  29                         unsigned int from_nid, unsigned int to_nid)
  30 {
  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;
  35 }
  36
  37 static ssize_t show_online(struct device *dev,
  38                            struct device_attribute *attr,
  39                            char *buf)
  40 {
  41         struct cpu *cpu = container_of(dev, struct cpu, dev);
  42
  43         return sprintf(buf, "%u\n", !!cpu_online(cpu->dev.id));
  44 }
  45
  46 static ssize_t __ref store_online(struct device *dev,
  47                                   struct device_attribute *attr,
  48                                   const char *buf, size_t count)
  49 {
  50         struct cpu *cpu = container_of(dev, struct cpu, dev);
  51         int cpuid = cpu->dev.id;
  52         int from_nid, to_nid;
  53         ssize_t ret;
  54
  55         cpu_hotplug_driver_lock();
  56         switch (buf[0]) {
  57         case '0':
  58                 ret = cpu_down(cpuid);
  59                 if (!ret)
  60                         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
  61                 break;
  62         case '1':
  63                 from_nid = cpu_to_node(cpuid);
  64                 ret = cpu_up(cpuid);
  65
  66                 /*
  67                  * When hot adding memory to memoryless node and enabling a cpu
  68                  * on the node, node number of the cpu may internally change.
  69                  */
  70                 to_nid = cpu_to_node(cpuid);
  71                 if (from_nid != to_nid)
  72                         change_cpu_under_node(cpu, from_nid, to_nid);
  73
  74                 if (!ret)
  75                         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
  76                 break;
  77         default:
  78                 ret = -EINVAL;
  79         }
  80         cpu_hotplug_driver_unlock();
  81
  82         if (ret >= 0)
  83                 ret = count;
  84         return ret;
  85 }
  86 static DEVICE_ATTR(online, 0644, show_online, store_online);
  87
  88 static void __cpuinit register_cpu_control(struct cpu *cpu)
  89 {
  90         device_create_file(&cpu->dev, &dev_attr_online);
  91 }
  92 void unregister_cpu(struct cpu *cpu)
  93 {
  94         int logical_cpu = cpu->dev.id;
  95
  96         unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
  97
  98         device_remove_file(&cpu->dev, &dev_attr_online);
  99
 100         device_unregister(&cpu->dev);
 101         per_cpu(cpu_sys_devices, logical_cpu) = NULL;
 102         return;
 103 }
 104
 105 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 106 static ssize_t cpu_probe_store(struct device *dev,
 107                                struct device_attribute *attr,
 108                                const char *buf,
 109                                size_t count)
 110 {
 111         return arch_cpu_probe(buf, count);
 112 }
 113
 114 static ssize_t cpu_release_store(struct device *dev,
 115                                  struct device_attribute *attr,
 116                                  const char *buf,
 117                                  size_t count)
 118 {
 119         return arch_cpu_release(buf, count);
 120 }
 121
 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 */
 125
 126 #else /* ... !CONFIG_HOTPLUG_CPU */
 127 static inline void register_cpu_control(struct cpu *cpu)
 128 {
 129 }
 130 #endif /* CONFIG_HOTPLUG_CPU */
 131
 132 #ifdef CONFIG_KEXEC
 133 #include <linux/kexec.h>
 134
 135 static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
 136                                 char *buf)
 137 {
 138         struct cpu *cpu = container_of(dev, struct cpu, dev);
 139         ssize_t rc;
 140         unsigned long long addr;
 141         int cpunum;
 142
 143         cpunum = cpu->dev.id;
 144
 145         /*
 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.
 150          */
 151         addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
 152         rc = sprintf(buf, "%Lx\n", addr);
 153         return rc;
 154 }
 155 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 156
 157 static ssize_t show_crash_notes_size(struct device *dev,
 158                                      struct device_attribute *attr,
 159                                      char *buf)
 160 {
 161         ssize_t rc;
 162
 163         rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
 164         return rc;
 165 }
 166 static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
 167 #endif
 168
 169 /*
 170  * Print cpu online, possible, present, and system maps
 171  */
 172
 173 struct cpu_attr {
 174         struct device_attribute attr;
 175         const struct cpumask *const * const map;
 176 };
 177
 178 static ssize_t show_cpus_attr(struct device *dev,
 179                               struct device_attribute *attr,
 180                               char *buf)
 181 {
 182         struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 183         int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
 184
 185         buf[n++] = '\n';
 186         buf[n] = '\0';
 187         return n;
 188 }
 189
 190 #define _CPU_ATTR(name, map) \
 191         { __ATTR(name, 0444, show_cpus_attr, NULL), map }
 192
 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),
 198 };
 199
 200 /*
 201  * Print values for NR_CPUS and offlined cpus
 202  */
 203 static ssize_t print_cpus_kernel_max(struct device *dev,
 204                                      struct device_attribute *attr, char *buf)
 205 {
 206         int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 207         return n;
 208 }
 209 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 210
 211 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 212 unsigned int total_cpus;
 213
 214 static ssize_t print_cpus_offline(struct device *dev,
 215                                   struct device_attribute *attr, char *buf)
 216 {
 217         int n = 0, len = PAGE_SIZE-2;
 218         cpumask_var_t offline;
 219
 220         /* display offline cpus < nr_cpu_ids */
 221         if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 222                 return -ENOMEM;
 223         cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 224         n = cpulist_scnprintf(buf, len, offline);
 225         free_cpumask_var(offline);
 226
 227         /* display offline cpus >= nr_cpu_ids */
 228         if (total_cpus && nr_cpu_ids < total_cpus) {
 229                 if (n && n < len)
 230                         buf[n++] = ',';
 231
 232                 if (nr_cpu_ids == total_cpus-1)
 233                         n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
 234                 else
 235                         n += snprintf(&buf[n], len - n, "%d-%d",
 236                                                       nr_cpu_ids, total_cpus-1);
 237         }
 238
 239         n += snprintf(&buf[n], len - n, "\n");
 240         return n;
 241 }
 242 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 243
 244 static void cpu_device_release(struct device *dev)
 245 {
 246         /*
 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
 256          * by the cpu device.
 257          *
 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.
 260          */
 261 }
 262
 263 /*
 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.
 268  *
 269  * Initialize and register the CPU device.
 270  */
 271 int __cpuinit register_cpu(struct cpu *cpu, int num)
 272 {
 273         int error;
 274
 275         cpu->node_id = cpu_to_node(num);
 276         memset(&cpu->dev, 0x00, sizeof(struct device));
 277         cpu->dev.id = num;
 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;
 282 #endif
 283         error = device_register(&cpu->dev);
 284         if (!error && cpu->hotpluggable)
 285                 register_cpu_control(cpu);
 286         if (!error)
 287                 per_cpu(cpu_sys_devices, num) = &cpu->dev;
 288         if (!error)
 289                 register_cpu_under_node(num, cpu_to_node(num));
 290
 291 #ifdef CONFIG_KEXEC
 292         if (!error)
 293                 error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
 294         if (!error)
 295                 error = device_create_file(&cpu->dev,
 296                                            &dev_attr_crash_notes_size);
 297 #endif
 298         return error;
 299 }
 300
 301 struct device *get_cpu_device(unsigned cpu)
 302 {
 303         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 304                 return per_cpu(cpu_sys_devices, cpu);
 305         else
 306                 return NULL;
 307 }
 308 EXPORT_SYMBOL_GPL(get_cpu_device);
 309
 310 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 311 static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
 312 #endif
 313
 314 static struct attribute *cpu_root_attrs[] = {
 315 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 316         &dev_attr_probe.attr,
 317         &dev_attr_release.attr,
 318 #endif
 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,
 326 #endif
 327         NULL
 328 };
 329
 330 static struct attribute_group cpu_root_attr_group = {
 331         .attrs = cpu_root_attrs,
 332 };
 333
 334 static const struct attribute_group *cpu_root_attr_groups[] = {
 335         &cpu_root_attr_group,
 336         NULL,
 337 };
 338
 339 bool cpu_is_hotpluggable(unsigned cpu)
 340 {
 341         struct device *dev = get_cpu_device(cpu);
 342         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 343 }
 344 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 345
 346 #ifdef CONFIG_GENERIC_CPU_DEVICES
 347 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 348 #endif
 349
 350 static void __init cpu_dev_register_generic(void)
 351 {
 352 #ifdef CONFIG_GENERIC_CPU_DEVICES
 353         int i;
 354
 355         for_each_possible_cpu(i) {
 356                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 357                         panic("Failed to register CPU device");
 358         }
 359 #endif
 360 }
 361
 362 void __init cpu_dev_init(void)
 363 {
 364         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 365                 panic("Failed to register CPU subsystem");
 366
 367         cpu_dev_register_generic();
 368 }