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 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
  37 static 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 }
  65 static DEVICE_ATTR(online, 0644, show_online, store_online);
  66
  67 static void __cpuinit register_cpu_control(struct cpu *cpu)
  68 {
  69         device_create_file(&cpu->dev, &dev_attr_online);
  70 }
  71 void 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
  85 static 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
  93 static 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
 101 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 102 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 103 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 104
 105 #else /* ... !CONFIG_HOTPLUG_CPU */
 106 static 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
 114 static 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 }
 134 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 135
 136 static ssize_t show_crash_notes_size(struct device *dev,
 137                                      struct device_attribute *attr,
 138                                      char *buf)
 139 {
 140         ssize_t rc;
 141
 142         rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
 143         return rc;
 144 }
 145 static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
 146 #endif
 147
 148 /*
 149  * Print cpu online, possible, present, and system maps
 150  */
 151
 152 struct cpu_attr {
 153         struct device_attribute attr;
 154         const struct cpumask *const * const map;
 155 };
 156
 157 static ssize_t show_cpus_attr(struct device *dev,
 158                               struct device_attribute *attr,
 159                               char *buf)
 160 {
 161         struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 162         int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
 163
 164         buf[n++] = '\n';
 165         buf[n] = '\0';
 166         return n;
 167 }
 168
 169 #define _CPU_ATTR(name, map) \
 170         { __ATTR(name, 0444, show_cpus_attr, NULL), map }
 171
 172 /* Keep in sync with cpu_subsys_attrs */
 173 static struct cpu_attr cpu_attrs[] = {
 174         _CPU_ATTR(online, &cpu_online_mask),
 175         _CPU_ATTR(possible, &cpu_possible_mask),
 176         _CPU_ATTR(present, &cpu_present_mask),
 177 };
 178
 179 /*
 180  * Print values for NR_CPUS and offlined cpus
 181  */
 182 static ssize_t print_cpus_kernel_max(struct device *dev,
 183                                      struct device_attribute *attr, char *buf)
 184 {
 185         int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 186         return n;
 187 }
 188 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 189
 190 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 191 unsigned int total_cpus;
 192
 193 static ssize_t print_cpus_offline(struct device *dev,
 194                                   struct device_attribute *attr, char *buf)
 195 {
 196         int n = 0, len = PAGE_SIZE-2;
 197         cpumask_var_t offline;
 198
 199         /* display offline cpus < nr_cpu_ids */
 200         if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 201                 return -ENOMEM;
 202         cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 203         n = cpulist_scnprintf(buf, len, offline);
 204         free_cpumask_var(offline);
 205
 206         /* display offline cpus >= nr_cpu_ids */
 207         if (total_cpus && nr_cpu_ids < total_cpus) {
 208                 if (n && n < len)
 209                         buf[n++] = ',';
 210
 211                 if (nr_cpu_ids == total_cpus-1)
 212                         n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
 213                 else
 214                         n += snprintf(&buf[n], len - n, "%d-%d",
 215                                                       nr_cpu_ids, total_cpus-1);
 216         }
 217
 218         n += snprintf(&buf[n], len - n, "\n");
 219         return n;
 220 }
 221 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 222
 223 static void cpu_device_release(struct device *dev)
 224 {
 225         /*
 226          * This is an empty function to prevent the driver core from spitting a
 227          * warning at us.  Yes, I know this is directly opposite of what the
 228          * documentation for the driver core and kobjects say, and the author
 229          * of this code has already been publically ridiculed for doing
 230          * something as foolish as this.  However, at this point in time, it is
 231          * the only way to handle the issue of statically allocated cpu
 232          * devices.  The different architectures will have their cpu device
 233          * code reworked to properly handle this in the near future, so this
 234          * function will then be changed to correctly free up the memory held
 235          * by the cpu device.
 236          *
 237          * Never copy this way of doing things, or you too will be made fun of
 238          * on the linux-kernel list, you have been warned.
 239          */
 240 }
 241
 242 /*
 243  * register_cpu - Setup a sysfs device for a CPU.
 244  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 245  *        sysfs for this CPU.
 246  * @num - CPU number to use when creating the device.
 247  *
 248  * Initialize and register the CPU device.
 249  */
 250 int __cpuinit register_cpu(struct cpu *cpu, int num)
 251 {
 252         int error;
 253
 254         cpu->node_id = cpu_to_node(num);
 255         memset(&cpu->dev, 0x00, sizeof(struct device));
 256         cpu->dev.id = num;
 257         cpu->dev.bus = &cpu_subsys;
 258         cpu->dev.release = cpu_device_release;
 259 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 260         cpu->dev.bus->uevent = arch_cpu_uevent;
 261 #endif
 262         error = device_register(&cpu->dev);
 263         if (!error && cpu->hotpluggable)
 264                 register_cpu_control(cpu);
 265         if (!error)
 266                 per_cpu(cpu_sys_devices, num) = &cpu->dev;
 267         if (!error)
 268                 register_cpu_under_node(num, cpu_to_node(num));
 269
 270 #ifdef CONFIG_KEXEC
 271         if (!error)
 272                 error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
 273         if (!error)
 274                 error = device_create_file(&cpu->dev,
 275                                            &dev_attr_crash_notes_size);
 276 #endif
 277         return error;
 278 }
 279
 280 struct device *get_cpu_device(unsigned cpu)
 281 {
 282         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 283                 return per_cpu(cpu_sys_devices, cpu);
 284         else
 285                 return NULL;
 286 }
 287 EXPORT_SYMBOL_GPL(get_cpu_device);
 288
 289 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 290 static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
 291 #endif
 292
 293 static struct attribute *cpu_root_attrs[] = {
 294 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 295         &dev_attr_probe.attr,
 296         &dev_attr_release.attr,
 297 #endif
 298         &cpu_attrs[0].attr.attr,
 299         &cpu_attrs[1].attr.attr,
 300         &cpu_attrs[2].attr.attr,
 301         &dev_attr_kernel_max.attr,
 302         &dev_attr_offline.attr,
 303 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 304         &dev_attr_modalias.attr,
 305 #endif
 306         NULL
 307 };
 308
 309 static struct attribute_group cpu_root_attr_group = {
 310         .attrs = cpu_root_attrs,
 311 };
 312
 313 static const struct attribute_group *cpu_root_attr_groups[] = {
 314         &cpu_root_attr_group,
 315         NULL,
 316 };
 317
 318 bool cpu_is_hotpluggable(unsigned cpu)
 319 {
 320         struct device *dev = get_cpu_device(cpu);
 321         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 322 }
 323 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 324
 325 #ifdef CONFIG_GENERIC_CPU_DEVICES
 326 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 327 #endif
 328
 329 static void __init cpu_dev_register_generic(void)
 330 {
 331 #ifdef CONFIG_GENERIC_CPU_DEVICES
 332         int i;
 333
 334         for_each_possible_cpu(i) {
 335                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 336                         panic("Failed to register CPU device");
 337         }
 338 #endif
 339 }
 340
 341 void __init cpu_dev_init(void)
 342 {
 343         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 344                 panic("Failed to register CPU subsystem");
 345
 346         cpu_dev_register_generic();
 347 }