x86: round_jiffies() for i386 and x86-64 non-critical/corrected MCE polling

[linux-2.6/mini2440.git] / arch / x86_64 / kernel / mce.c

/*
 * Machine check handler.
 * K8 parts Copyright 2002,2003 Andi Kleen, SuSE Labs.
 * Rest from unknown author(s). 
 * 2004 Andi Kleen. Rewrote most of it. 
 */

#include <linux/init.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
#include <linux/sysdev.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/poll.h>
#include <linux/thread_info.h>
#include <linux/ctype.h>
#include <linux/kmod.h>
#include <linux/kdebug.h>
#include <asm/processor.h> 
#include <asm/msr.h>
#include <asm/mce.h>
#include <asm/uaccess.h>
#include <asm/smp.h>
#include <asm/idle.h>

#define MISC_MCELOG_MINOR 227
#define NR_BANKS 6

atomic_t mce_entry;

static int mce_dont_init;

/*
 * Tolerant levels:
 *   0: always panic on uncorrected errors, log corrected errors
 *   1: panic or SIGBUS on uncorrected errors, log corrected errors
 *   2: SIGBUS or log uncorrected errors (if possible), log corrected errors
 *   3: never panic or SIGBUS, log all errors (for testing only)
 */
static int tolerant = 1;
static int banks;
static unsigned long bank[NR_BANKS] = { [0 ... NR_BANKS-1] = ~0UL };
static unsigned long notify_user;
static int rip_msr;
static int mce_bootlog = 1;
static atomic_t mce_events;

static char trigger[128];
static char *trigger_argv[2] = { trigger, NULL };

static DECLARE_WAIT_QUEUE_HEAD(mce_wait);

/*
 * Lockless MCE logging infrastructure.
 * This avoids deadlocks on printk locks without having to break locks. Also
 * separate MCEs from kernel messages to avoid bogus bug reports.
 */

struct mce_log mcelog = { 
        MCE_LOG_SIGNATURE,
        MCE_LOG_LEN,
}; 

void mce_log(struct mce *mce)
{
        unsigned next, entry;
        atomic_inc(&mce_events);
        mce->finished = 0;
        wmb();
        for (;;) {
                entry = rcu_dereference(mcelog.next);
                /* The rmb forces the compiler to reload next in each
                    iteration */
                rmb();
                for (;;) {
                        /* When the buffer fills up discard new entries. Assume
                           that the earlier errors are the more interesting. */
                        if (entry >= MCE_LOG_LEN) {
                                set_bit(MCE_OVERFLOW, &mcelog.flags);
                                return;
                        }
                        /* Old left over entry. Skip. */
                        if (mcelog.entry[entry].finished) {
                                entry++;
                                continue;
                        }
                        break;
                }
                smp_rmb();
                next = entry + 1;
                if (cmpxchg(&mcelog.next, entry, next) == entry)
                        break;
        }
        memcpy(mcelog.entry + entry, mce, sizeof(struct mce));
        wmb();
        mcelog.entry[entry].finished = 1;
        wmb();

        set_bit(0, &notify_user);
}

static void print_mce(struct mce *m)
{
        printk(KERN_EMERG "\n"
               KERN_EMERG "HARDWARE ERROR\n"
               KERN_EMERG
               "CPU %d: Machine Check Exception: %16Lx Bank %d: %016Lx\n",
               m->cpu, m->mcgstatus, m->bank, m->status);
        if (m->rip) {
                printk(KERN_EMERG 
                       "RIP%s %02x:<%016Lx> ",
                       !(m->mcgstatus & MCG_STATUS_EIPV) ? " !INEXACT!" : "",
                       m->cs, m->rip);
                if (m->cs == __KERNEL_CS)
                        print_symbol("{%s}", m->rip);
                printk("\n");
        }
        printk(KERN_EMERG "TSC %Lx ", m->tsc); 
        if (m->addr)
                printk("ADDR %Lx ", m->addr);
        if (m->misc)
                printk("MISC %Lx ", m->misc);   
        printk("\n");
        printk(KERN_EMERG "This is not a software problem!\n");
        printk(KERN_EMERG
    "Run through mcelog --ascii to decode and contact your hardware vendor\n");
}

static void mce_panic(char *msg, struct mce *backup, unsigned long start)
{ 
        int i;

        oops_begin();
        for (i = 0; i < MCE_LOG_LEN; i++) {
                unsigned long tsc = mcelog.entry[i].tsc;
                if (time_before(tsc, start))
                        continue;
                print_mce(&mcelog.entry[i]); 
                if (backup && mcelog.entry[i].tsc == backup->tsc)
                        backup = NULL;
        }
        if (backup)
                print_mce(backup);
        panic(msg);
} 

static int mce_available(struct cpuinfo_x86 *c)
{
        return cpu_has(c, X86_FEATURE_MCE) && cpu_has(c, X86_FEATURE_MCA);
}

static inline void mce_get_rip(struct mce *m, struct pt_regs *regs)
{
        if (regs && (m->mcgstatus & MCG_STATUS_RIPV)) {
                m->rip = regs->rip;
                m->cs = regs->cs;
        } else {
                m->rip = 0;
                m->cs = 0;
        }
        if (rip_msr) {
                /* Assume the RIP in the MSR is exact. Is this true? */
                m->mcgstatus |= MCG_STATUS_EIPV;
                rdmsrl(rip_msr, m->rip);
                m->cs = 0;
        }
}

/* 
 * The actual machine check handler
 */

void do_machine_check(struct pt_regs * regs, long error_code)
{
        struct mce m, panicm;
        u64 mcestart = 0;
        int i;
        int panicm_found = 0;
        /*
         * If no_way_out gets set, there is no safe way to recover from this
         * MCE.  If tolerant is cranked up, we'll try anyway.
         */
        int no_way_out = 0;
        /*
         * If kill_it gets set, there might be a way to recover from this
         * error.
         */
        int kill_it = 0;

        atomic_inc(&mce_entry);

        if (regs)
                notify_die(DIE_NMI, "machine check", regs, error_code, 18, SIGKILL);
        if (!banks)
                goto out2;

        memset(&m, 0, sizeof(struct mce));
        m.cpu = smp_processor_id();
        rdmsrl(MSR_IA32_MCG_STATUS, m.mcgstatus);
        /* if the restart IP is not valid, we're done for */
        if (!(m.mcgstatus & MCG_STATUS_RIPV))
                no_way_out = 1;
        
        rdtscll(mcestart);
        barrier();

        for (i = 0; i < banks; i++) {
                if (!bank[i])
                        continue;
                
                m.misc = 0; 
                m.addr = 0;
                m.bank = i;
                m.tsc = 0;

                rdmsrl(MSR_IA32_MC0_STATUS + i*4, m.status);
                if ((m.status & MCI_STATUS_VAL) == 0)
                        continue;

                if (m.status & MCI_STATUS_EN) {
                        /* if PCC was set, there's no way out */
                        no_way_out |= !!(m.status & MCI_STATUS_PCC);
                        /*
                         * If this error was uncorrectable and there was
                         * an overflow, we're in trouble.  If no overflow,
                         * we might get away with just killing a task.
                         */
                        if (m.status & MCI_STATUS_UC) {
                                if (tolerant < 1 || m.status & MCI_STATUS_OVER)
                                        no_way_out = 1;
                                kill_it = 1;
                        }
                }

                if (m.status & MCI_STATUS_MISCV)
                        rdmsrl(MSR_IA32_MC0_MISC + i*4, m.misc);
                if (m.status & MCI_STATUS_ADDRV)
                        rdmsrl(MSR_IA32_MC0_ADDR + i*4, m.addr);

                mce_get_rip(&m, regs);
                if (error_code >= 0)
                        rdtscll(m.tsc);
                if (error_code != -2)
                        mce_log(&m);

                /* Did this bank cause the exception? */
                /* Assume that the bank with uncorrectable errors did it,
                   and that there is only a single one. */
                if ((m.status & MCI_STATUS_UC) && (m.status & MCI_STATUS_EN)) {
                        panicm = m;
                        panicm_found = 1;
                }

                add_taint(TAINT_MACHINE_CHECK);
        }

        /* Never do anything final in the polling timer */
        if (!regs)
                goto out;

        /* If we didn't find an uncorrectable error, pick
           the last one (shouldn't happen, just being safe). */
        if (!panicm_found)
                panicm = m;

        /*
         * If we have decided that we just CAN'T continue, and the user
         *  has not set tolerant to an insane level, give up and die.
         */
        if (no_way_out && tolerant < 3)
                mce_panic("Machine check", &panicm, mcestart);

        /*
         * If the error seems to be unrecoverable, something should be
         * done.  Try to kill as little as possible.  If we can kill just
         * one task, do that.  If the user has set the tolerance very
         * high, don't try to do anything at all.
         */
        if (kill_it && tolerant < 3) {
                int user_space = 0;

                /*
                 * If the EIPV bit is set, it means the saved IP is the
                 * instruction which caused the MCE.
                 */
                if (m.mcgstatus & MCG_STATUS_EIPV)
                        user_space = panicm.rip && (panicm.cs & 3);

                /*
                 * If we know that the error was in user space, send a
                 * SIGBUS.  Otherwise, panic if tolerance is low.
                 *
                 * do_exit() takes an awful lot of locks and has a slight
                 * risk of deadlocking.
                 */
                if (user_space) {
                        do_exit(SIGBUS);
                } else if (panic_on_oops || tolerant < 2) {
                        mce_panic("Uncorrected machine check",
                                &panicm, mcestart);
                }
        }

        /* notify userspace ASAP */
        set_thread_flag(TIF_MCE_NOTIFY);

 out:
        /* the last thing we do is clear state */
        for (i = 0; i < banks; i++)
                wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0);
        wrmsrl(MSR_IA32_MCG_STATUS, 0);
 out2:
        atomic_dec(&mce_entry);
}

#ifdef CONFIG_X86_MCE_INTEL
/***
 * mce_log_therm_throt_event - Logs the thermal throttling event to mcelog
 * @cpu: The CPU on which the event occured.
 * @status: Event status information
 *
 * This function should be called by the thermal interrupt after the
 * event has been processed and the decision was made to log the event
 * further.
 *
 * The status parameter will be saved to the 'status' field of 'struct mce'
 * and historically has been the register value of the
 * MSR_IA32_THERMAL_STATUS (Intel) msr.
 */
void mce_log_therm_throt_event(unsigned int cpu, __u64 status)
{
        struct mce m;

        memset(&m, 0, sizeof(m));
        m.cpu = cpu;
        m.bank = MCE_THERMAL_BANK;
        m.status = status;
        rdtscll(m.tsc);
        mce_log(&m);
}
#endif /* CONFIG_X86_MCE_INTEL */

/*
 * Periodic polling timer for "silent" machine check errors.  If the
 * poller finds an MCE, poll 2x faster.  When the poller finds no more
 * errors, poll 2x slower (up to check_interval seconds).
 */

static int check_interval = 5 * 60; /* 5 minutes */
static int next_interval; /* in jiffies */
static void mcheck_timer(struct work_struct *work);
static DECLARE_DELAYED_WORK(mcheck_work, mcheck_timer);

static void mcheck_check_cpu(void *info)
{
        if (mce_available(&current_cpu_data))
                do_machine_check(NULL, 0);
}

static void mcheck_timer(struct work_struct *work)
{
        on_each_cpu(mcheck_check_cpu, NULL, 1, 1);

        /*
         * Alert userspace if needed.  If we logged an MCE, reduce the
         * polling interval, otherwise increase the polling interval.
         */
        if (mce_notify_user()) {
                next_interval = max(next_interval/2, HZ/100);
        } else {
                next_interval = min(next_interval*2,
                                (int)round_jiffies_relative(check_interval*HZ));
        }

        schedule_delayed_work(&mcheck_work, next_interval);
}

/*
 * This is only called from process context.  This is where we do
 * anything we need to alert userspace about new MCEs.  This is called
 * directly from the poller and also from entry.S and idle, thanks to
 * TIF_MCE_NOTIFY.
 */
int mce_notify_user(void)
{
        clear_thread_flag(TIF_MCE_NOTIFY);
        if (test_and_clear_bit(0, &notify_user)) {
                static unsigned long last_print;
                unsigned long now = jiffies;

                wake_up_interruptible(&mce_wait);
                if (trigger[0])
                        call_usermodehelper(trigger, trigger_argv, NULL,
                                                UMH_NO_WAIT);

                if (time_after_eq(now, last_print + (check_interval*HZ))) {
                        last_print = now;
                        printk(KERN_INFO "Machine check events logged\n");
                }

                return 1;
        }
        return 0;
}

/* see if the idle task needs to notify userspace */
static int
mce_idle_callback(struct notifier_block *nfb, unsigned long action, void *junk)
{
        /* IDLE_END should be safe - interrupts are back on */
        if (action == IDLE_END && test_thread_flag(TIF_MCE_NOTIFY))
                mce_notify_user();

        return NOTIFY_OK;
}

static struct notifier_block mce_idle_notifier = {
        .notifier_call = mce_idle_callback,
};

static __init int periodic_mcheck_init(void)
{ 
        next_interval = check_interval * HZ;
        if (next_interval)
                schedule_delayed_work(&mcheck_work,
                                      round_jiffies_relative(next_interval));
        idle_notifier_register(&mce_idle_notifier);
        return 0;
} 
__initcall(periodic_mcheck_init);


/* 
 * Initialize Machine Checks for a CPU.
 */
static void mce_init(void *dummy)
{
        u64 cap;
        int i;

        rdmsrl(MSR_IA32_MCG_CAP, cap);
        banks = cap & 0xff;
        if (banks > NR_BANKS) { 
                printk(KERN_INFO "MCE: warning: using only %d banks\n", banks);
                banks = NR_BANKS; 
        }
        /* Use accurate RIP reporting if available. */
        if ((cap & (1<<9)) && ((cap >> 16) & 0xff) >= 9)
                rip_msr = MSR_IA32_MCG_EIP;

        /* Log the machine checks left over from the previous reset.
           This also clears all registers */
        do_machine_check(NULL, mce_bootlog ? -1 : -2);

        set_in_cr4(X86_CR4_MCE);

        if (cap & MCG_CTL_P)
                wrmsr(MSR_IA32_MCG_CTL, 0xffffffff, 0xffffffff);

        for (i = 0; i < banks; i++) {
                wrmsrl(MSR_IA32_MC0_CTL+4*i, bank[i]);
                wrmsrl(MSR_IA32_MC0_STATUS+4*i, 0);
        }       
}

/* Add per CPU specific workarounds here */
static void __cpuinit mce_cpu_quirks(struct cpuinfo_x86 *c)
{ 
        /* This should be disabled by the BIOS, but isn't always */
        if (c->x86_vendor == X86_VENDOR_AMD && c->x86 == 15) {
                /* disable GART TBL walk error reporting, which trips off 
                   incorrectly with the IOMMU & 3ware & Cerberus. */
                clear_bit(10, &bank[4]);
                /* Lots of broken BIOS around that don't clear them
                   by default and leave crap in there. Don't log. */
                mce_bootlog = 0;
        }

}                       

static void __cpuinit mce_cpu_features(struct cpuinfo_x86 *c)
{
        switch (c->x86_vendor) {
        case X86_VENDOR_INTEL:
                mce_intel_feature_init(c);
                break;
        case X86_VENDOR_AMD:
                mce_amd_feature_init(c);
                break;
        default:
                break;
        }
}

/* 
 * Called for each booted CPU to set up machine checks.
 * Must be called with preempt off. 
 */
void __cpuinit mcheck_init(struct cpuinfo_x86 *c)
{
        static cpumask_t mce_cpus = CPU_MASK_NONE;

        mce_cpu_quirks(c); 

        if (mce_dont_init ||
            cpu_test_and_set(smp_processor_id(), mce_cpus) ||
            !mce_available(c))
                return;

        mce_init(NULL);
        mce_cpu_features(c);
}

/*
 * Character device to read and clear the MCE log.
 */

static DEFINE_SPINLOCK(mce_state_lock);
static int open_count;  /* #times opened */
static int open_exclu;  /* already open exclusive? */

static int mce_open(struct inode *inode, struct file *file)
{
        spin_lock(&mce_state_lock);

        if (open_exclu || (open_count && (file->f_flags & O_EXCL))) {
                spin_unlock(&mce_state_lock);
                return -EBUSY;
        }

        if (file->f_flags & O_EXCL)
                open_exclu = 1;
        open_count++;

        spin_unlock(&mce_state_lock);

        return nonseekable_open(inode, file);
}

static int mce_release(struct inode *inode, struct file *file)
{
        spin_lock(&mce_state_lock);

        open_count--;
        open_exclu = 0;

        spin_unlock(&mce_state_lock);

        return 0;
}

static void collect_tscs(void *data) 
{ 
        unsigned long *cpu_tsc = (unsigned long *)data;
        rdtscll(cpu_tsc[smp_processor_id()]);
} 

static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize, loff_t *off)
{
        unsigned long *cpu_tsc;
        static DECLARE_MUTEX(mce_read_sem);
        unsigned next;
        char __user *buf = ubuf;
        int i, err;

        cpu_tsc = kmalloc(NR_CPUS * sizeof(long), GFP_KERNEL);
        if (!cpu_tsc)
                return -ENOMEM;

        down(&mce_read_sem); 
        next = rcu_dereference(mcelog.next);

        /* Only supports full reads right now */
        if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce)) { 
                up(&mce_read_sem);
                kfree(cpu_tsc);
                return -EINVAL;
        }

        err = 0;
        for (i = 0; i < next; i++) {            
                unsigned long start = jiffies;
                while (!mcelog.entry[i].finished) {
                        if (time_after_eq(jiffies, start + 2)) {
                                memset(mcelog.entry + i,0, sizeof(struct mce));
                                goto timeout;
                        }
                        cpu_relax();
                }
                smp_rmb();
                err |= copy_to_user(buf, mcelog.entry + i, sizeof(struct mce));
                buf += sizeof(struct mce); 
 timeout:
                ;
        } 

        memset(mcelog.entry, 0, next * sizeof(struct mce));
        mcelog.next = 0;

        synchronize_sched();

        /* Collect entries that were still getting written before the synchronize. */

        on_each_cpu(collect_tscs, cpu_tsc, 1, 1);
        for (i = next; i < MCE_LOG_LEN; i++) { 
                if (mcelog.entry[i].finished && 
                    mcelog.entry[i].tsc < cpu_tsc[mcelog.entry[i].cpu]) {  
                        err |= copy_to_user(buf, mcelog.entry+i, sizeof(struct mce));
                        smp_rmb();
                        buf += sizeof(struct mce);
                        memset(&mcelog.entry[i], 0, sizeof(struct mce));
                }
        }       
        up(&mce_read_sem);
        kfree(cpu_tsc);
        return err ? -EFAULT : buf - ubuf; 
}

static unsigned int mce_poll(struct file *file, poll_table *wait)
{
        poll_wait(file, &mce_wait, wait);
        if (rcu_dereference(mcelog.next))
                return POLLIN | POLLRDNORM;
        return 0;
}

static int mce_ioctl(struct inode *i, struct file *f,unsigned int cmd, unsigned long arg)
{
        int __user *p = (int __user *)arg;
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM; 
        switch (cmd) {
        case MCE_GET_RECORD_LEN: 
                return put_user(sizeof(struct mce), p);
        case MCE_GET_LOG_LEN:
                return put_user(MCE_LOG_LEN, p);                
        case MCE_GETCLEAR_FLAGS: {
                unsigned flags;
                do { 
                        flags = mcelog.flags;
                } while (cmpxchg(&mcelog.flags, flags, 0) != flags); 
                return put_user(flags, p); 
        }
        default:
                return -ENOTTY; 
        } 
}

static const struct file_operations mce_chrdev_ops = {
        .open = mce_open,
        .release = mce_release,
        .read = mce_read,
        .poll = mce_poll,
        .ioctl = mce_ioctl,
};

static struct miscdevice mce_log_device = {
        MISC_MCELOG_MINOR,
        "mcelog",
        &mce_chrdev_ops,
};

/* 
 * Old style boot options parsing. Only for compatibility. 
 */

static int __init mcheck_disable(char *str)
{
        mce_dont_init = 1;
        return 1;
}

/* mce=off disables machine check. Note you can reenable it later
   using sysfs.
   mce=TOLERANCELEVEL (number, see above)
   mce=bootlog Log MCEs from before booting. Disabled by default on AMD.
   mce=nobootlog Don't log MCEs from before booting. */
static int __init mcheck_enable(char *str)
{
        if (*str == '=')
                str++;
        if (!strcmp(str, "off"))
                mce_dont_init = 1;
        else if (!strcmp(str, "bootlog") || !strcmp(str,"nobootlog"))
                mce_bootlog = str[0] == 'b';
        else if (isdigit(str[0]))
                get_option(&str, &tolerant);
        else
                printk("mce= argument %s ignored. Please use /sys", str); 
        return 1;
}

__setup("nomce", mcheck_disable);
__setup("mce", mcheck_enable);

/* 
 * Sysfs support
 */ 

/* On resume clear all MCE state. Don't want to see leftovers from the BIOS.
   Only one CPU is active at this time, the others get readded later using
   CPU hotplug. */
static int mce_resume(struct sys_device *dev)
{
        mce_init(NULL);
        return 0;
}

/* Reinit MCEs after user configuration changes */
static void mce_restart(void) 
{ 
        if (next_interval)
                cancel_delayed_work(&mcheck_work);
        /* Timer race is harmless here */
        on_each_cpu(mce_init, NULL, 1, 1);       
        next_interval = check_interval * HZ;
        if (next_interval)
                schedule_delayed_work(&mcheck_work,
                                      round_jiffies_relative(next_interval));
}

static struct sysdev_class mce_sysclass = {
        .resume = mce_resume,
        set_kset_name("machinecheck"),
};

DEFINE_PER_CPU(struct sys_device, device_mce);

/* Why are there no generic functions for this? */
#define ACCESSOR(name, var, start) \
        static ssize_t show_ ## name(struct sys_device *s, char *buf) {                    \
                return sprintf(buf, "%lx\n", (unsigned long)var);                  \
        }                                                                          \
        static ssize_t set_ ## name(struct sys_device *s,const char *buf,size_t siz) { \
                char *end;                                                         \
                unsigned long new = simple_strtoul(buf, &end, 0);                  \
                if (end == buf) return -EINVAL;                                    \
                var = new;                                                         \
                start;                                                             \
                return end-buf;                                                    \
        }                                                                          \
        static SYSDEV_ATTR(name, 0644, show_ ## name, set_ ## name);

/* TBD should generate these dynamically based on number of available banks */
ACCESSOR(bank0ctl,bank[0],mce_restart())
ACCESSOR(bank1ctl,bank[1],mce_restart())
ACCESSOR(bank2ctl,bank[2],mce_restart())
ACCESSOR(bank3ctl,bank[3],mce_restart())
ACCESSOR(bank4ctl,bank[4],mce_restart())
ACCESSOR(bank5ctl,bank[5],mce_restart())

static ssize_t show_trigger(struct sys_device *s, char *buf)
{
        strcpy(buf, trigger);
        strcat(buf, "\n");
        return strlen(trigger) + 1;
}

static ssize_t set_trigger(struct sys_device *s,const char *buf,size_t siz)
{
        char *p;
        int len;
        strncpy(trigger, buf, sizeof(trigger));
        trigger[sizeof(trigger)-1] = 0;
        len = strlen(trigger);
        p = strchr(trigger, '\n');
        if (*p) *p = 0;
        return len;
}

static SYSDEV_ATTR(trigger, 0644, show_trigger, set_trigger);
ACCESSOR(tolerant,tolerant,)
ACCESSOR(check_interval,check_interval,mce_restart())
static struct sysdev_attribute *mce_attributes[] = {
        &attr_bank0ctl, &attr_bank1ctl, &attr_bank2ctl,
        &attr_bank3ctl, &attr_bank4ctl, &attr_bank5ctl,
        &attr_tolerant, &attr_check_interval, &attr_trigger,
        NULL
};

/* Per cpu sysdev init.  All of the cpus still share the same ctl bank */
static __cpuinit int mce_create_device(unsigned int cpu)
{
        int err;
        int i;
        if (!mce_available(&cpu_data[cpu]))
                return -EIO;

        per_cpu(device_mce,cpu).id = cpu;
        per_cpu(device_mce,cpu).cls = &mce_sysclass;

        err = sysdev_register(&per_cpu(device_mce,cpu));

        if (!err) {
                for (i = 0; mce_attributes[i]; i++)
                        sysdev_create_file(&per_cpu(device_mce,cpu),
                                mce_attributes[i]);
        }
        return err;
}

static void mce_remove_device(unsigned int cpu)
{
        int i;

        for (i = 0; mce_attributes[i]; i++)
                sysdev_remove_file(&per_cpu(device_mce,cpu),
                        mce_attributes[i]);
        sysdev_unregister(&per_cpu(device_mce,cpu));
        memset(&per_cpu(device_mce, cpu).kobj, 0, sizeof(struct kobject));
}

/* Get notified when a cpu comes on/off. Be hotplug friendly. */
static int
mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
        unsigned int cpu = (unsigned long)hcpu;

        switch (action) {
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                mce_create_device(cpu);
                break;
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
                mce_remove_device(cpu);
                break;
        }
        return NOTIFY_OK;
}

static struct notifier_block mce_cpu_notifier = {
        .notifier_call = mce_cpu_callback,
};

static __init int mce_init_device(void)
{
        int err;
        int i = 0;

        if (!mce_available(&boot_cpu_data))
                return -EIO;
        err = sysdev_class_register(&mce_sysclass);

        for_each_online_cpu(i) {
                mce_create_device(i);
        }

        register_hotcpu_notifier(&mce_cpu_notifier);
        misc_register(&mce_log_device);
        return err;
}

device_initcall(mce_init_device);