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 struct attribute *hotplug_cpu_attrs[] = {
  89         &dev_attr_online.attr,
  90         NULL
  91 };
  92
  93 static struct attribute_group hotplug_cpu_attr_group = {
  94         .attrs = hotplug_cpu_attrs,
  95 };
  96
  97 void unregister_cpu(struct cpu *cpu)
  98 {
  99         int logical_cpu = cpu->dev.id;
 100
 101         unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
 102
 103         device_unregister(&cpu->dev);
 104         per_cpu(cpu_sys_devices, logical_cpu) = NULL;
 105         return;
 106 }
 107
 108 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 109 static ssize_t cpu_probe_store(struct device *dev,
 110                                struct device_attribute *attr,
 111                                const char *buf,
 112                                size_t count)
 113 {
 114         return arch_cpu_probe(buf, count);
 115 }
 116
 117 static ssize_t cpu_release_store(struct device *dev,
 118                                  struct device_attribute *attr,
 119                                  const char *buf,
 120                                  size_t count)
 121 {
 122         return arch_cpu_release(buf, count);
 123 }
 124
 125 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 126 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 127 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 128 #endif /* CONFIG_HOTPLUG_CPU */
 129
 130 #ifdef CONFIG_KEXEC
 131 #include <linux/kexec.h>
 132
 133 static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
 134                                 char *buf)
 135 {
 136         struct cpu *cpu = container_of(dev, struct cpu, dev);
 137         ssize_t rc;
 138         unsigned long long addr;
 139         int cpunum;
 140
 141         cpunum = cpu->dev.id;
 142
 143         /*
 144          * Might be reading other cpu's data based on which cpu read thread
 145          * has been scheduled. But cpu data (memory) is allocated once during
 146          * boot up and this data does not change there after. Hence this
 147          * operation should be safe. No locking required.
 148          */
 149         addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
 150         rc = sprintf(buf, "%Lx\n", addr);
 151         return rc;
 152 }
 153 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 154
 155 static ssize_t show_crash_notes_size(struct device *dev,
 156                                      struct device_attribute *attr,
 157                                      char *buf)
 158 {
 159         ssize_t rc;
 160
 161         rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
 162         return rc;
 163 }
 164 static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
 165
 166 static struct attribute *crash_note_cpu_attrs[] = {
 167         &dev_attr_crash_notes.attr,
 168         &dev_attr_crash_notes_size.attr,
 169         NULL
 170 };
 171
 172 static struct attribute_group crash_note_cpu_attr_group = {
 173         .attrs = crash_note_cpu_attrs,
 174 };
 175 #endif
 176
 177 static const struct attribute_group *common_cpu_attr_groups[] = {
 178 #ifdef CONFIG_KEXEC
 179         &crash_note_cpu_attr_group,
 180 #endif
 181         NULL
 182 };
 183
 184 static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
 185 #ifdef CONFIG_KEXEC
 186         &crash_note_cpu_attr_group,
 187 #endif
 188 #ifdef CONFIG_HOTPLUG_CPU
 189         &hotplug_cpu_attr_group,
 190 #endif
 191         NULL
 192 };
 193
 194 /*
 195  * Print cpu online, possible, present, and system maps
 196  */
 197
 198 struct cpu_attr {
 199         struct device_attribute attr;
 200         const struct cpumask *const * const map;
 201 };
 202
 203 static ssize_t show_cpus_attr(struct device *dev,
 204                               struct device_attribute *attr,
 205                               char *buf)
 206 {
 207         struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 208         int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
 209
 210         buf[n++] = '\n';
 211         buf[n] = '\0';
 212         return n;
 213 }
 214
 215 #define _CPU_ATTR(name, map) \
 216         { __ATTR(name, 0444, show_cpus_attr, NULL), map }
 217
 218 /* Keep in sync with cpu_subsys_attrs */
 219 static struct cpu_attr cpu_attrs[] = {
 220         _CPU_ATTR(online, &cpu_online_mask),
 221         _CPU_ATTR(possible, &cpu_possible_mask),
 222         _CPU_ATTR(present, &cpu_present_mask),
 223 };
 224
 225 /*
 226  * Print values for NR_CPUS and offlined cpus
 227  */
 228 static ssize_t print_cpus_kernel_max(struct device *dev,
 229                                      struct device_attribute *attr, char *buf)
 230 {
 231         int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 232         return n;
 233 }
 234 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 235
 236 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 237 unsigned int total_cpus;
 238
 239 static ssize_t print_cpus_offline(struct device *dev,
 240                                   struct device_attribute *attr, char *buf)
 241 {
 242         int n = 0, len = PAGE_SIZE-2;
 243         cpumask_var_t offline;
 244
 245         /* display offline cpus < nr_cpu_ids */
 246         if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 247                 return -ENOMEM;
 248         cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 249         n = cpulist_scnprintf(buf, len, offline);
 250         free_cpumask_var(offline);
 251
 252         /* display offline cpus >= nr_cpu_ids */
 253         if (total_cpus && nr_cpu_ids < total_cpus) {
 254                 if (n && n < len)
 255                         buf[n++] = ',';
 256
 257                 if (nr_cpu_ids == total_cpus-1)
 258                         n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
 259                 else
 260                         n += snprintf(&buf[n], len - n, "%d-%d",
 261                                                       nr_cpu_ids, total_cpus-1);
 262         }
 263
 264         n += snprintf(&buf[n], len - n, "\n");
 265         return n;
 266 }
 267 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 268
 269 static void cpu_device_release(struct device *dev)
 270 {
 271         /*
 272          * This is an empty function to prevent the driver core from spitting a
 273          * warning at us.  Yes, I know this is directly opposite of what the
 274          * documentation for the driver core and kobjects say, and the author
 275          * of this code has already been publically ridiculed for doing
 276          * something as foolish as this.  However, at this point in time, it is
 277          * the only way to handle the issue of statically allocated cpu
 278          * devices.  The different architectures will have their cpu device
 279          * code reworked to properly handle this in the near future, so this
 280          * function will then be changed to correctly free up the memory held
 281          * by the cpu device.
 282          *
 283          * Never copy this way of doing things, or you too will be made fun of
 284          * on the linux-kernel list, you have been warned.
 285          */
 286 }
 287
 288 /*
 289  * register_cpu - Setup a sysfs device for a CPU.
 290  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 291  *        sysfs for this CPU.
 292  * @num - CPU number to use when creating the device.
 293  *
 294  * Initialize and register the CPU device.
 295  */
 296 int __cpuinit register_cpu(struct cpu *cpu, int num)
 297 {
 298         int error;
 299
 300         cpu->node_id = cpu_to_node(num);
 301         memset(&cpu->dev, 0x00, sizeof(struct device));
 302         cpu->dev.id = num;
 303         cpu->dev.bus = &cpu_subsys;
 304         cpu->dev.release = cpu_device_release;
 305 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 306         cpu->dev.bus->uevent = arch_cpu_uevent;
 307 #endif
 308         cpu->dev.groups = common_cpu_attr_groups;
 309         if (cpu->hotpluggable)
 310                 cpu->dev.groups = hotplugable_cpu_attr_groups;
 311         error = device_register(&cpu->dev);
 312         if (!error)
 313                 per_cpu(cpu_sys_devices, num) = &cpu->dev;
 314         if (!error)
 315                 register_cpu_under_node(num, cpu_to_node(num));
 316
 317         return error;
 318 }
 319
 320 struct device *get_cpu_device(unsigned cpu)
 321 {
 322         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 323                 return per_cpu(cpu_sys_devices, cpu);
 324         else
 325                 return NULL;
 326 }
 327 EXPORT_SYMBOL_GPL(get_cpu_device);
 328
 329 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 330 static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
 331 #endif
 332
 333 static struct attribute *cpu_root_attrs[] = {
 334 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 335         &dev_attr_probe.attr,
 336         &dev_attr_release.attr,
 337 #endif
 338         &cpu_attrs[0].attr.attr,
 339         &cpu_attrs[1].attr.attr,
 340         &cpu_attrs[2].attr.attr,
 341         &dev_attr_kernel_max.attr,
 342         &dev_attr_offline.attr,
 343 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 344         &dev_attr_modalias.attr,
 345 #endif
 346         NULL
 347 };
 348
 349 static struct attribute_group cpu_root_attr_group = {
 350         .attrs = cpu_root_attrs,
 351 };
 352
 353 static const struct attribute_group *cpu_root_attr_groups[] = {
 354         &cpu_root_attr_group,
 355         NULL,
 356 };
 357
 358 bool cpu_is_hotpluggable(unsigned cpu)
 359 {
 360         struct device *dev = get_cpu_device(cpu);
 361         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 362 }
 363 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 364
 365 #ifdef CONFIG_GENERIC_CPU_DEVICES
 366 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 367 #endif
 368
 369 static void __init cpu_dev_register_generic(void)
 370 {
 371 #ifdef CONFIG_GENERIC_CPU_DEVICES
 372         int i;
 373
 374         for_each_possible_cpu(i) {
 375                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 376                         panic("Failed to register CPU device");
 377         }
 378 #endif
 379 }
 380
 381 void __init cpu_dev_init(void)
 382 {
 383         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 384                 panic("Failed to register CPU subsystem");
 385
 386         cpu_dev_register_generic();
 387 }