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