drivers/base/cpu.c

   1 /*
   2  * CPU subsystem support
   3  */
   4
   5 #include <linux/module.h>
   6 #include <linux/init.h>
   7 #include <linux/sched.h>
   8 #include <linux/cpu.h>
   9 #include <linux/topology.h>
  10 #include <linux/device.h>
  11 #include <linux/node.h>
  12 #include <linux/gfp.h>
  13
  14 #include "base.h"
  15
  16 struct bus_type cpu_subsys = {
  17         .name = "cpu",
  18         .dev_name = "cpu",
  19 };
  20 EXPORT_SYMBOL_GPL(cpu_subsys);
  21
  22 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
  23
  24 #ifdef CONFIG_HOTPLUG_CPU
  25 static ssize_t show_online(struct device *dev,
  26                            struct device_attribute *attr,
  27                            char *buf)
  28 {
  29         struct cpu *cpu = container_of(dev, struct cpu, dev);
  30
  31         return sprintf(buf, "%u\n", !!cpu_online(cpu->dev.id));
  32 }
  33
  34 static ssize_t __ref store_online(struct device *dev,
  35                                   struct device_attribute *attr,
  36                                   const char *buf, size_t count)
  37 {
  38         struct cpu *cpu = container_of(dev, struct cpu, dev);
  39         ssize_t ret;
  40
  41         cpu_hotplug_driver_lock();
  42         switch (buf[0]) {
  43         case '0':
  44                 ret = cpu_down(cpu->dev.id);
  45                 if (!ret)
  46                         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
  47                 break;
  48         case '1':
  49                 ret = cpu_up(cpu->dev.id);
  50                 if (!ret)
  51                         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
  52                 break;
  53         default:
  54                 ret = -EINVAL;
  55         }
  56         cpu_hotplug_driver_unlock();
  57
  58         if (ret >= 0)
  59                 ret = count;
  60         return ret;
  61 }
  62 static DEVICE_ATTR(online, 0644, show_online, store_online);
  63
  64 static void __cpuinit register_cpu_control(struct cpu *cpu)
  65 {
  66         device_create_file(&cpu->dev, &dev_attr_online);
  67 }
  68 void unregister_cpu(struct cpu *cpu)
  69 {
  70         int logical_cpu = cpu->dev.id;
  71
  72         unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
  73
  74         device_remove_file(&cpu->dev, &dev_attr_online);
  75
  76         device_unregister(&cpu->dev);
  77         per_cpu(cpu_sys_devices, logical_cpu) = NULL;
  78         return;
  79 }
  80
  81 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
  82 static ssize_t cpu_probe_store(struct device *dev,
  83                                struct device_attribute *attr,
  84                                const char *buf,
  85                                size_t count)
  86 {
  87         return arch_cpu_probe(buf, count);
  88 }
  89
  90 static ssize_t cpu_release_store(struct device *dev,
  91                                  struct device_attribute *attr,
  92                                  const char *buf,
  93                                  size_t count)
  94 {
  95         return arch_cpu_release(buf, count);
  96 }
  97
  98 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
  99 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 100 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 101
 102 #else /* ... !CONFIG_HOTPLUG_CPU */
 103 static inline void register_cpu_control(struct cpu *cpu)
 104 {
 105 }
 106 #endif /* CONFIG_HOTPLUG_CPU */
 107
 108 #ifdef CONFIG_KEXEC
 109 #include <linux/kexec.h>
 110
 111 static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
 112                                 char *buf)
 113 {
 114         struct cpu *cpu = container_of(dev, struct cpu, dev);
 115         ssize_t rc;
 116         unsigned long long addr;
 117         int cpunum;
 118
 119         cpunum = cpu->dev.id;
 120
 121         /*
 122          * Might be reading other cpu's data based on which cpu read thread
 123          * has been scheduled. But cpu data (memory) is allocated once during
 124          * boot up and this data does not change there after. Hence this
 125          * operation should be safe. No locking required.
 126          */
 127         addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
 128         rc = sprintf(buf, "%Lx\n", addr);
 129         return rc;
 130 }
 131 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 132 #endif
 133
 134 /*
 135  * Print cpu online, possible, present, and system maps
 136  */
 137
 138 struct cpu_attr {
 139         struct device_attribute attr;
 140         const struct cpumask *const * const map;
 141 };
 142
 143 static ssize_t show_cpus_attr(struct device *dev,
 144                               struct device_attribute *attr,
 145                               char *buf)
 146 {
 147         struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 148         int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));
 149
 150         buf[n++] = '\n';
 151         buf[n] = '\0';
 152         return n;
 153 }
 154
 155 #define _CPU_ATTR(name, map) \
 156         { __ATTR(name, 0444, show_cpus_attr, NULL), map }
 157
 158 /* Keep in sync with cpu_subsys_attrs */
 159 static struct cpu_attr cpu_attrs[] = {
 160         _CPU_ATTR(online, &cpu_online_mask),
 161         _CPU_ATTR(possible, &cpu_possible_mask),
 162         _CPU_ATTR(present, &cpu_present_mask),
 163 };
 164
 165 /*
 166  * Print values for NR_CPUS and offlined cpus
 167  */
 168 static ssize_t print_cpus_kernel_max(struct device *dev,
 169                                      struct device_attribute *attr, char *buf)
 170 {
 171         int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 172         return n;
 173 }
 174 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 175
 176 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 177 unsigned int total_cpus;
 178
 179 static ssize_t print_cpus_offline(struct device *dev,
 180                                   struct device_attribute *attr, char *buf)
 181 {
 182         int n = 0, len = PAGE_SIZE-2;
 183         cpumask_var_t offline;
 184
 185         /* display offline cpus < nr_cpu_ids */
 186         if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 187                 return -ENOMEM;
 188         cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 189         n = cpulist_scnprintf(buf, len, offline);
 190         free_cpumask_var(offline);
 191
 192         /* display offline cpus >= nr_cpu_ids */
 193         if (total_cpus && nr_cpu_ids < total_cpus) {
 194                 if (n && n < len)
 195                         buf[n++] = ',';
 196
 197                 if (nr_cpu_ids == total_cpus-1)
 198                         n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
 199                 else
 200                         n += snprintf(&buf[n], len - n, "%d-%d",
 201                                                       nr_cpu_ids, total_cpus-1);
 202         }
 203
 204         n += snprintf(&buf[n], len - n, "\n");
 205         return n;
 206 }
 207 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 208
 209 /*
 210  * register_cpu - Setup a sysfs device for a CPU.
 211  * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 212  *        sysfs for this CPU.
 213  * @num - CPU number to use when creating the device.
 214  *
 215  * Initialize and register the CPU device.
 216  */
 217 int __cpuinit register_cpu(struct cpu *cpu, int num)
 218 {
 219         int error;
 220
 221         cpu->node_id = cpu_to_node(num);
 222         cpu->dev.id = num;
 223         cpu->dev.bus = &cpu_subsys;
 224         error = device_register(&cpu->dev);
 225         if (!error && cpu->hotpluggable)
 226                 register_cpu_control(cpu);
 227         if (!error)
 228                 per_cpu(cpu_sys_devices, num) = &cpu->dev;
 229         if (!error)
 230                 register_cpu_under_node(num, cpu_to_node(num));
 231
 232 #ifdef CONFIG_KEXEC
 233         if (!error)
 234                 error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
 235 #endif
 236         return error;
 237 }
 238
 239 struct device *get_cpu_device(unsigned cpu)
 240 {
 241         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 242                 return per_cpu(cpu_sys_devices, cpu);
 243         else
 244                 return NULL;
 245 }
 246 EXPORT_SYMBOL_GPL(get_cpu_device);
 247
 248 static struct attribute *cpu_root_attrs[] = {
 249 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 250         &dev_attr_probe.attr,
 251         &dev_attr_release.attr,
 252 #endif
 253         &cpu_attrs[0].attr.attr,
 254         &cpu_attrs[1].attr.attr,
 255         &cpu_attrs[2].attr.attr,
 256         &dev_attr_kernel_max.attr,
 257         &dev_attr_offline.attr,
 258         NULL
 259 };
 260
 261 static struct attribute_group cpu_root_attr_group = {
 262         .attrs = cpu_root_attrs,
 263 };
 264
 265 static const struct attribute_group *cpu_root_attr_groups[] = {
 266         &cpu_root_attr_group,
 267         NULL,
 268 };
 269
 270 bool cpu_is_hotpluggable(unsigned cpu)
 271 {
 272         struct device *dev = get_cpu_device(cpu);
 273         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 274 }
 275 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 276
 277 int __init cpu_dev_init(void)
 278 {
 279         int err;
 280
 281         err = subsys_system_register(&cpu_subsys, cpu_root_attr_groups);
 282         if (err)
 283                 return err;
 284
 285 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
 286         err = sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
 287 #endif
 288         return err;
 289 }