cpu.c

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/*
 * CPU subsystem support
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/cpu.h>
#include <linux/topology.h>
#include <linux/device.h>
#include <linux/node.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/percpu.h>

#include "base.h"

struct bus_type cpu_subsys = {
    .name = "cpu",
    .dev_name = "cpu",
};
EXPORT_SYMBOL_GPL(cpu_subsys);

static DEFINE_PER_CPU(struct device *, cpu_sys_devices);

#ifdef CONFIG_HOTPLUG_CPU
static ssize_t show_online(struct device *dev,
               struct device_attribute *attr,
               char *buf)
{
    struct cpu *cpu = container_of(dev, struct cpu, dev);

    return sprintf(buf, "%u\n", !!cpu_online(cpu->dev.id));
}

static ssize_t __ref store_online(struct device *dev,
                  struct device_attribute *attr,
                  const char *buf, size_t count)
{
    struct cpu *cpu = container_of(dev, struct cpu, dev);
    ssize_t ret;

    cpu_hotplug_driver_lock();
    switch (buf[0]) {
    case '0':
        ret = cpu_down(cpu->dev.id);
        if (!ret)
            kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
        break;
    case '1':
        ret = cpu_up(cpu->dev.id);
        if (!ret)
            kobject_uevent(&dev->kobj, KOBJ_ONLINE);
        break;
    default:
        ret = -EINVAL;
    }
    cpu_hotplug_driver_unlock();

    if (ret >= 0)
        ret = count;
    return ret;
}
static DEVICE_ATTR(online, 0644, show_online, store_online);

static void __cpuinit register_cpu_control(struct cpu *cpu)
{
    device_create_file(&cpu->dev, &dev_attr_online);
}
void unregister_cpu(struct cpu *cpu)
{
    int logical_cpu = cpu->dev.id;

    unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));

    device_remove_file(&cpu->dev, &dev_attr_online);

    device_unregister(&cpu->dev);
    per_cpu(cpu_sys_devices, logical_cpu) = NULL;
    return;
}

#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
static ssize_t cpu_probe_store(struct device *dev,
                   struct device_attribute *attr,
                   const char *buf,
                   size_t count)
{
    return arch_cpu_probe(buf, count);
}

static ssize_t cpu_release_store(struct device *dev,
                 struct device_attribute *attr,
                 const char *buf,
                 size_t count)
{
    return arch_cpu_release(buf, count);
}

static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */

#else /* ... !CONFIG_HOTPLUG_CPU */
static inline void register_cpu_control(struct cpu *cpu)
{
}
#endif /* CONFIG_HOTPLUG_CPU */

#ifdef CONFIG_KEXEC
#include <linux/kexec.h>

static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
                char *buf)
{
    struct cpu *cpu = container_of(dev, struct cpu, dev);
    ssize_t rc;
    unsigned long long addr;
    int cpunum;

    cpunum = cpu->dev.id;

    /*
     * Might be reading other cpu's data based on which cpu read thread
     * has been scheduled. But cpu data (memory) is allocated once during
     * boot up and this data does not change there after. Hence this
     * operation should be safe. No locking required.
     */
    addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
    rc = sprintf(buf, "%Lx\n", addr);
    return rc;
}
static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
#endif

/*
 * Print cpu online, possible, present, and system maps
 */

struct cpu_attr {
    struct device_attribute attr;
    const struct cpumask *const * const map;
};

static ssize_t show_cpus_attr(struct device *dev,
                  struct device_attribute *attr,
                  char *buf)
{
    struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
    int n = cpulist_scnprintf(buf, PAGE_SIZE-2, *(ca->map));

    buf[n++] = '\n';
    buf[n] = '\0';
    return n;
}

#define _CPU_ATTR(name, map) \
    { __ATTR(name, 0444, show_cpus_attr, NULL), map }

/* Keep in sync with cpu_subsys_attrs */
static struct cpu_attr cpu_attrs[] = {
    _CPU_ATTR(online, &cpu_online_mask),
    _CPU_ATTR(possible, &cpu_possible_mask),
    _CPU_ATTR(present, &cpu_present_mask),
};

/*
 * Print values for NR_CPUS and offlined cpus
 */
static ssize_t print_cpus_kernel_max(struct device *dev,
                     struct device_attribute *attr, char *buf)
{
    int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
    return n;
}
static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);

/* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
unsigned int total_cpus;

static ssize_t print_cpus_offline(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    int n = 0, len = PAGE_SIZE-2;
    cpumask_var_t offline;

    /* display offline cpus < nr_cpu_ids */
    if (!alloc_cpumask_var(&offline, GFP_KERNEL))
        return -ENOMEM;
    cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
    n = cpulist_scnprintf(buf, len, offline);
    free_cpumask_var(offline);

    /* display offline cpus >= nr_cpu_ids */
    if (total_cpus && nr_cpu_ids < total_cpus) {
        if (n && n < len)
            buf[n++] = ',';

        if (nr_cpu_ids == total_cpus-1)
            n += snprintf(&buf[n], len - n, "%d", nr_cpu_ids);
        else
            n += snprintf(&buf[n], len - n, "%d-%d",
                              nr_cpu_ids, total_cpus-1);
    }

    n += snprintf(&buf[n], len - n, "\n");
    return n;
}
static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);

static void cpu_device_release(struct device *dev)
{
    /*
     * This is an empty function to prevent the driver core from spitting a
     * warning at us.  Yes, I know this is directly opposite of what the
     * documentation for the driver core and kobjects say, and the author
     * of this code has already been publically ridiculed for doing
     * something as foolish as this.  However, at this point in time, it is
     * the only way to handle the issue of statically allocated cpu
     * devices.  The different architectures will have their cpu device
     * code reworked to properly handle this in the near future, so this
     * function will then be changed to correctly free up the memory held
     * by the cpu device.
     *
     * Never copy this way of doing things, or you too will be made fun of
     * on the linux-kerenl list, you have been warned.
     */
}

/*
 * register_cpu - Setup a sysfs device for a CPU.
 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 *    sysfs for this CPU.
 * @num - CPU number to use when creating the device.
 *
 * Initialize and register the CPU device.
 */
int __cpuinit register_cpu(struct cpu *cpu, int num)
{
    int error;

    cpu->node_id = cpu_to_node(num);
    memset(&cpu->dev, 0x00, sizeof(struct device));
    cpu->dev.id = num;
    cpu->dev.bus = &cpu_subsys;
    cpu->dev.release = cpu_device_release;
#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
    cpu->dev.bus->uevent = arch_cpu_uevent;
#endif
    error = device_register(&cpu->dev);
    if (!error && cpu->hotpluggable)
        register_cpu_control(cpu);
    if (!error)
        per_cpu(cpu_sys_devices, num) = &cpu->dev;
    if (!error)
        register_cpu_under_node(num, cpu_to_node(num));

#ifdef CONFIG_KEXEC
    if (!error)
        error = device_create_file(&cpu->dev, &dev_attr_crash_notes);
#endif
    return error;
}

struct device *get_cpu_device(unsigned cpu)
{
    if (cpu < nr_cpu_ids && cpu_possible(cpu))
        return per_cpu(cpu_sys_devices, cpu);
    else
        return NULL;
}
EXPORT_SYMBOL_GPL(get_cpu_device);

#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
static DEVICE_ATTR(modalias, 0444, arch_print_cpu_modalias, NULL);
#endif

static struct attribute *cpu_root_attrs[] = {
#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
    &dev_attr_probe.attr,
    &dev_attr_release.attr,
#endif
    &cpu_attrs[0].attr.attr,
    &cpu_attrs[1].attr.attr,
    &cpu_attrs[2].attr.attr,
    &dev_attr_kernel_max.attr,
    &dev_attr_offline.attr,
#ifdef CONFIG_ARCH_HAS_CPU_AUTOPROBE
    &dev_attr_modalias.attr,
#endif
    NULL
};

static struct attribute_group cpu_root_attr_group = {
    .attrs = cpu_root_attrs,
};

static const struct attribute_group *cpu_root_attr_groups[] = {
    &cpu_root_attr_group,
    NULL,
};

bool cpu_is_hotpluggable(unsigned cpu)
{
    struct device *dev = get_cpu_device(cpu);
    return dev && container_of(dev, struct cpu, dev)->hotpluggable;
}
EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);

#ifdef CONFIG_GENERIC_CPU_DEVICES
static DEFINE_PER_CPU(struct cpu, cpu_devices);
#endif

static void __init cpu_dev_register_generic(void)
{
#ifdef CONFIG_GENERIC_CPU_DEVICES
    int i;

    for_each_possible_cpu(i) {
        if (register_cpu(&per_cpu(cpu_devices, i), i))
            panic("Failed to register CPU device");
    }
#endif
}

void __init cpu_dev_init(void)
{
    if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
        panic("Failed to register CPU subsystem");

    cpu_dev_register_generic();
}