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 #endif
 136
 137 /*
 138  * Print cpu online, possible, present, and system maps
 139  */
 140
 141 struct cpu_attr {
 142         struct device_attribute attr;
 143         const struct cpumask *const * const map;
 144 };
 145
 146 static 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 */
 162 static 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  */
 171 static 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 }
 177 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 178
 179 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 180 unsigned int total_cpus;
 181
 182 static 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 }
 210 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 211
 212 static 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-kerenl 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  */
 239 int __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
 266 struct 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 }
 273 EXPORT_SYMBOL_GPL(get_cpu_device);
 274
 275 #ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
 276 static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
 277 #endif
 278
 279 static 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
 295 static struct attribute_group cpu_root_attr_group = {
 296         .attrs = cpu_root_attrs,
 297 };
 298
 299 static const struct attribute_group *cpu_root_attr_groups[] = {
 300         &cpu_root_attr_group,
 301         NULL,
 302 };
 303
 304 bool 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 }
 309 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 310
 311 #ifdef CONFIG_GENERIC_CPU_DEVICES
 312 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 313 #endif
 314
 315 static 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
 327 void __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 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
 335         sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
 336 #endif
 337 }