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smp.c

/*
 *  arch/s390/kernel/smp.c
 *
 *    Copyright IBM Corp. 1999,2007
 *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
 *           Martin Schwidefsky (schwidefsky@de.ibm.com)
 *           Heiko Carstens (heiko.carstens@de.ibm.com)
 *
 *  based on other smp stuff by
 *    (c) 1995 Alan Cox, CymruNET Ltd  <alan@cymru.net>
 *    (c) 1998 Ingo Molnar
 *
 * We work with logical cpu numbering everywhere we can. The only
 * functions using the real cpu address (got from STAP) are the sigp
 * functions. For all other functions we use the identity mapping.
 * That means that cpu_number_map[i] == i for every cpu. cpu_number_map is
 * used e.g. to find the idle task belonging to a logical cpu. Every array
 * in the kernel is sorted by the logical cpu number and not by the physical
 * one which is causing all the confusion with __cpu_logical_map and
 * cpu_number_map in other architectures.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/kernel_stat.h>
#include <linux/delay.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/timex.h>
#include <linux/bootmem.h>
#include <asm/ipl.h>
#include <asm/setup.h>
#include <asm/sigp.h>
#include <asm/pgalloc.h>
#include <asm/irq.h>
#include <asm/s390_ext.h>
#include <asm/cpcmd.h>
#include <asm/tlbflush.h>
#include <asm/timer.h>
#include <asm/lowcore.h>
#include <asm/cpu.h>

/*
 * An array with a pointer the lowcore of every CPU.
 */
struct _lowcore *lowcore_ptr[NR_CPUS];
EXPORT_SYMBOL(lowcore_ptr);

cpumask_t cpu_online_map = CPU_MASK_NONE;
EXPORT_SYMBOL(cpu_online_map);

cpumask_t cpu_possible_map = CPU_MASK_NONE;
EXPORT_SYMBOL(cpu_possible_map);

static struct task_struct *current_set[NR_CPUS];

static void smp_ext_bitcall(int, ec_bit_sig);

/*
 * Structure and data for __smp_call_function_map(). This is designed to
 * minimise static memory requirements. It also looks cleaner.
 */
static DEFINE_SPINLOCK(call_lock);

struct call_data_struct {
      void (*func) (void *info);
      void *info;
      cpumask_t started;
      cpumask_t finished;
      int wait;
};

static struct call_data_struct *call_data;

/*
 * 'Call function' interrupt callback
 */
static void do_call_function(void)
{
      void (*func) (void *info) = call_data->func;
      void *info = call_data->info;
      int wait = call_data->wait;

      cpu_set(smp_processor_id(), call_data->started);
      (*func)(info);
      if (wait)
            cpu_set(smp_processor_id(), call_data->finished);;
}

static void __smp_call_function_map(void (*func) (void *info), void *info,
                            int nonatomic, int wait, cpumask_t map)
{
      struct call_data_struct data;
      int cpu, local = 0;

      /*
       * Can deadlock when interrupts are disabled or if in wrong context.
       */
      WARN_ON(irqs_disabled() || in_irq());

      /*
       * Check for local function call. We have to have the same call order
       * as in on_each_cpu() because of machine_restart_smp().
       */
      if (cpu_isset(smp_processor_id(), map)) {
            local = 1;
            cpu_clear(smp_processor_id(), map);
      }

      cpus_and(map, map, cpu_online_map);
      if (cpus_empty(map))
            goto out;

      data.func = func;
      data.info = info;
      data.started = CPU_MASK_NONE;
      data.wait = wait;
      if (wait)
            data.finished = CPU_MASK_NONE;

      spin_lock(&call_lock);
      call_data = &data;

      for_each_cpu_mask(cpu, map)
            smp_ext_bitcall(cpu, ec_call_function);

      /* Wait for response */
      while (!cpus_equal(map, data.started))
            cpu_relax();
      if (wait)
            while (!cpus_equal(map, data.finished))
                  cpu_relax();
      spin_unlock(&call_lock);
out:
      if (local) {
            local_irq_disable();
            func(info);
            local_irq_enable();
      }
}

/*
 * smp_call_function:
 * @func: the function to run; this must be fast and non-blocking
 * @info: an arbitrary pointer to pass to the function
 * @nonatomic: unused
 * @wait: if true, wait (atomically) until function has completed on other CPUs
 *
 * Run a function on all other CPUs.
 *
 * You must not call this function with disabled interrupts, from a
 * hardware interrupt handler or from a bottom half.
 */
int smp_call_function(void (*func) (void *info), void *info, int nonatomic,
                  int wait)
{
      cpumask_t map;

      preempt_disable();
      map = cpu_online_map;
      cpu_clear(smp_processor_id(), map);
      __smp_call_function_map(func, info, nonatomic, wait, map);
      preempt_enable();
      return 0;
}
EXPORT_SYMBOL(smp_call_function);

/*
 * smp_call_function_single:
 * @cpu: the CPU where func should run
 * @func: the function to run; this must be fast and non-blocking
 * @info: an arbitrary pointer to pass to the function
 * @nonatomic: unused
 * @wait: if true, wait (atomically) until function has completed on other CPUs
 *
 * Run a function on one processor.
 *
 * You must not call this function with disabled interrupts, from a
 * hardware interrupt handler or from a bottom half.
 */
int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
                       int nonatomic, int wait)
{
      preempt_disable();
      __smp_call_function_map(func, info, nonatomic, wait,
                        cpumask_of_cpu(cpu));
      preempt_enable();
      return 0;
}
EXPORT_SYMBOL(smp_call_function_single);

void smp_send_stop(void)
{
      int cpu, rc;

      /* Disable all interrupts/machine checks */
      __load_psw_mask(psw_kernel_bits & ~PSW_MASK_MCHECK);

      /* write magic number to zero page (absolute 0) */
      lowcore_ptr[smp_processor_id()]->panic_magic = __PANIC_MAGIC;

      /* stop all processors */
      for_each_online_cpu(cpu) {
            if (cpu == smp_processor_id())
                  continue;
            do {
                  rc = signal_processor(cpu, sigp_stop);
            } while (rc == sigp_busy);

            while (!smp_cpu_not_running(cpu))
                  cpu_relax();
      }
}

/*
 * Reboot, halt and power_off routines for SMP.
 */
void machine_restart_smp(char *__unused)
{
      smp_send_stop();
      do_reipl();
}

void machine_halt_smp(void)
{
      smp_send_stop();
      if (MACHINE_IS_VM && strlen(vmhalt_cmd) > 0)
            __cpcmd(vmhalt_cmd, NULL, 0, NULL);
      signal_processor(smp_processor_id(), sigp_stop_and_store_status);
      for (;;);
}

void machine_power_off_smp(void)
{
      smp_send_stop();
      if (MACHINE_IS_VM && strlen(vmpoff_cmd) > 0)
            __cpcmd(vmpoff_cmd, NULL, 0, NULL);
      signal_processor(smp_processor_id(), sigp_stop_and_store_status);
      for (;;);
}

/*
 * This is the main routine where commands issued by other
 * cpus are handled.
 */

static void do_ext_call_interrupt(__u16 code)
{
      unsigned long bits;

      /*
       * handle bit signal external calls
       *
       * For the ec_schedule signal we have to do nothing. All the work
       * is done automatically when we return from the interrupt.
       */
      bits = xchg(&S390_lowcore.ext_call_fast, 0);

      if (test_bit(ec_call_function, &bits))
            do_call_function();
}

/*
 * Send an external call sigp to another cpu and return without waiting
 * for its completion.
 */
static void smp_ext_bitcall(int cpu, ec_bit_sig sig)
{
      /*
       * Set signaling bit in lowcore of target cpu and kick it
       */
      set_bit(sig, (unsigned long *) &lowcore_ptr[cpu]->ext_call_fast);
      while (signal_processor(cpu, sigp_emergency_signal) == sigp_busy)
            udelay(10);
}

#ifndef CONFIG_64BIT
/*
 * this function sends a 'purge tlb' signal to another CPU.
 */
void smp_ptlb_callback(void *info)
{
      __tlb_flush_local();
}

void smp_ptlb_all(void)
{
      on_each_cpu(smp_ptlb_callback, NULL, 0, 1);
}
EXPORT_SYMBOL(smp_ptlb_all);
#endif /* ! CONFIG_64BIT */

/*
 * this function sends a 'reschedule' IPI to another CPU.
 * it goes straight through and wastes no time serializing
 * anything. Worst case is that we lose a reschedule ...
 */
void smp_send_reschedule(int cpu)
{
      smp_ext_bitcall(cpu, ec_schedule);
}

/*
 * parameter area for the set/clear control bit callbacks
 */
struct ec_creg_mask_parms {
      unsigned long orvals[16];
      unsigned long andvals[16];
};

/*
 * callback for setting/clearing control bits
 */
static void smp_ctl_bit_callback(void *info)
{
      struct ec_creg_mask_parms *pp = info;
      unsigned long cregs[16];
      int i;

      __ctl_store(cregs, 0, 15);
      for (i = 0; i <= 15; i++)
            cregs[i] = (cregs[i] & pp->andvals[i]) | pp->orvals[i];
      __ctl_load(cregs, 0, 15);
}

/*
 * Set a bit in a control register of all cpus
 */
void smp_ctl_set_bit(int cr, int bit)
{
      struct ec_creg_mask_parms parms;

      memset(&parms.orvals, 0, sizeof(parms.orvals));
      memset(&parms.andvals, 0xff, sizeof(parms.andvals));
      parms.orvals[cr] = 1 << bit;
      on_each_cpu(smp_ctl_bit_callback, &parms, 0, 1);
}
EXPORT_SYMBOL(smp_ctl_set_bit);

/*
 * Clear a bit in a control register of all cpus
 */
void smp_ctl_clear_bit(int cr, int bit)
{
      struct ec_creg_mask_parms parms;

      memset(&parms.orvals, 0, sizeof(parms.orvals));
      memset(&parms.andvals, 0xff, sizeof(parms.andvals));
      parms.andvals[cr] = ~(1L << bit);
      on_each_cpu(smp_ctl_bit_callback, &parms, 0, 1);
}
EXPORT_SYMBOL(smp_ctl_clear_bit);

#if defined(CONFIG_ZFCPDUMP) || defined(CONFIG_ZFCPDUMP_MODULE)

/*
 * zfcpdump_prefix_array holds prefix registers for the following scenario:
 * 64 bit zfcpdump kernel and 31 bit kernel which is to be dumped. We have to
 * save its prefix registers, since they get lost, when switching from 31 bit
 * to 64 bit.
 */
unsigned int zfcpdump_prefix_array[NR_CPUS + 1] \
      __attribute__((__section__(".data")));

static void __init smp_get_save_area(unsigned int cpu, unsigned int phy_cpu)
{
      if (ipl_info.type != IPL_TYPE_FCP_DUMP)
            return;
      if (cpu >= NR_CPUS) {
            printk(KERN_WARNING "Registers for cpu %i not saved since dump "
                   "kernel was compiled with NR_CPUS=%i\n", cpu, NR_CPUS);
            return;
      }
      zfcpdump_save_areas[cpu] = alloc_bootmem(sizeof(union save_area));
      __cpu_logical_map[1] = (__u16) phy_cpu;
      while (signal_processor(1, sigp_stop_and_store_status) == sigp_busy)
            cpu_relax();
      memcpy(zfcpdump_save_areas[cpu],
             (void *)(unsigned long) store_prefix() + SAVE_AREA_BASE,
             SAVE_AREA_SIZE);
#ifdef CONFIG_64BIT
      /* copy original prefix register */
      zfcpdump_save_areas[cpu]->s390x.pref_reg = zfcpdump_prefix_array[cpu];
#endif
}

union save_area *zfcpdump_save_areas[NR_CPUS + 1];
EXPORT_SYMBOL_GPL(zfcpdump_save_areas);

#else

static inline void smp_get_save_area(unsigned int cpu, unsigned int phy_cpu) { }

#endif /* CONFIG_ZFCPDUMP || CONFIG_ZFCPDUMP_MODULE */

/*
 * Lets check how many CPUs we have.
 */
static unsigned int __init smp_count_cpus(void)
{
      unsigned int cpu, num_cpus;
      __u16 boot_cpu_addr;

      /*
       * cpu 0 is the boot cpu. See smp_prepare_boot_cpu.
       */
      boot_cpu_addr = S390_lowcore.cpu_data.cpu_addr;
      current_thread_info()->cpu = 0;
      num_cpus = 1;
      for (cpu = 0; cpu <= 65535; cpu++) {
            if ((__u16) cpu == boot_cpu_addr)
                  continue;
            __cpu_logical_map[1] = (__u16) cpu;
            if (signal_processor(1, sigp_sense) == sigp_not_operational)
                  continue;
            smp_get_save_area(num_cpus, cpu);
            num_cpus++;
      }
      printk("Detected %d CPU's\n", (int) num_cpus);
      printk("Boot cpu address %2X\n", boot_cpu_addr);
      return num_cpus;
}

/*
 *    Activate a secondary processor.
 */
int __cpuinit start_secondary(void *cpuvoid)
{
      /* Setup the cpu */
      cpu_init();
      preempt_disable();
      /* Enable TOD clock interrupts on the secondary cpu. */
      init_cpu_timer();
#ifdef CONFIG_VIRT_TIMER
      /* Enable cpu timer interrupts on the secondary cpu. */
      init_cpu_vtimer();
#endif
      /* Enable pfault pseudo page faults on this cpu. */
      pfault_init();

      /* Mark this cpu as online */
      cpu_set(smp_processor_id(), cpu_online_map);
      /* Switch on interrupts */
      local_irq_enable();
      /* Print info about this processor */
      print_cpu_info(&S390_lowcore.cpu_data);
      /* cpu_idle will call schedule for us */
      cpu_idle();
      return 0;
}

DEFINE_PER_CPU(struct s390_idle_data, s390_idle);

static void __init smp_create_idle(unsigned int cpu)
{
      struct task_struct *p;

      /*
       *  don't care about the psw and regs settings since we'll never
       *  reschedule the forked task.
       */
      p = fork_idle(cpu);
      if (IS_ERR(p))
            panic("failed fork for CPU %u: %li", cpu, PTR_ERR(p));
      current_set[cpu] = p;
      spin_lock_init(&(&per_cpu(s390_idle, cpu))->lock);
}

static int cpu_stopped(int cpu)
{
      __u32 status;

      /* Check for stopped state */
      if (signal_processor_ps(&status, 0, cpu, sigp_sense) ==
          sigp_status_stored) {
            if (status & 0x40)
                  return 1;
      }
      return 0;
}

/* Upping and downing of CPUs */

int __cpu_up(unsigned int cpu)
{
      struct task_struct *idle;
      struct _lowcore *cpu_lowcore;
      struct stack_frame *sf;
      sigp_ccode ccode;
      int curr_cpu;

      for (curr_cpu = 0; curr_cpu <= 65535; curr_cpu++) {
            __cpu_logical_map[cpu] = (__u16) curr_cpu;
            if (cpu_stopped(cpu))
                  break;
      }

      if (!cpu_stopped(cpu))
            return -ENODEV;

      ccode = signal_processor_p((__u32)(unsigned long)(lowcore_ptr[cpu]),
                           cpu, sigp_set_prefix);
      if (ccode) {
            printk("sigp_set_prefix failed for cpu %d "
                   "with condition code %d\n",
                   (int) cpu, (int) ccode);
            return -EIO;
      }

      idle = current_set[cpu];
      cpu_lowcore = lowcore_ptr[cpu];
      cpu_lowcore->kernel_stack = (unsigned long)
            task_stack_page(idle) + THREAD_SIZE;
      sf = (struct stack_frame *) (cpu_lowcore->kernel_stack
                             - sizeof(struct pt_regs)
                             - sizeof(struct stack_frame));
      memset(sf, 0, sizeof(struct stack_frame));
      sf->gprs[9] = (unsigned long) sf;
      cpu_lowcore->save_area[15] = (unsigned long) sf;
      __ctl_store(cpu_lowcore->cregs_save_area[0], 0, 15);
      asm volatile(
            "     stam  0,15,0(%0)"
            : : "a" (&cpu_lowcore->access_regs_save_area) : "memory");
      cpu_lowcore->percpu_offset = __per_cpu_offset[cpu];
      cpu_lowcore->current_task = (unsigned long) idle;
      cpu_lowcore->cpu_data.cpu_nr = cpu;
      eieio();

      while (signal_processor(cpu, sigp_restart) == sigp_busy)
            udelay(10);

      while (!cpu_online(cpu))
            cpu_relax();
      return 0;
}

static unsigned int __initdata additional_cpus;
static unsigned int __initdata possible_cpus;

void __init smp_setup_cpu_possible_map(void)
{
      unsigned int phy_cpus, pos_cpus, cpu;

      phy_cpus = smp_count_cpus();
      pos_cpus = min(phy_cpus + additional_cpus, (unsigned int) NR_CPUS);

      if (possible_cpus)
            pos_cpus = min(possible_cpus, (unsigned int) NR_CPUS);

      for (cpu = 0; cpu < pos_cpus; cpu++)
            cpu_set(cpu, cpu_possible_map);

      phy_cpus = min(phy_cpus, pos_cpus);

      for (cpu = 0; cpu < phy_cpus; cpu++)
            cpu_set(cpu, cpu_present_map);
}

#ifdef CONFIG_HOTPLUG_CPU

static int __init setup_additional_cpus(char *s)
{
      additional_cpus = simple_strtoul(s, NULL, 0);
      return 0;
}
early_param("additional_cpus", setup_additional_cpus);

static int __init setup_possible_cpus(char *s)
{
      possible_cpus = simple_strtoul(s, NULL, 0);
      return 0;
}
early_param("possible_cpus", setup_possible_cpus);

int __cpu_disable(void)
{
      struct ec_creg_mask_parms cr_parms;
      int cpu = smp_processor_id();

      cpu_clear(cpu, cpu_online_map);

      /* Disable pfault pseudo page faults on this cpu. */
      pfault_fini();

      memset(&cr_parms.orvals, 0, sizeof(cr_parms.orvals));
      memset(&cr_parms.andvals, 0xff, sizeof(cr_parms.andvals));

      /* disable all external interrupts */
      cr_parms.orvals[0] = 0;
      cr_parms.andvals[0] = ~(1 << 15 | 1 << 14 | 1 << 13 | 1 << 12 |
                        1 << 11 | 1 << 10 | 1 <<  6 | 1 <<  4);
      /* disable all I/O interrupts */
      cr_parms.orvals[6] = 0;
      cr_parms.andvals[6] = ~(1 << 31 | 1 << 30 | 1 << 29 | 1 << 28 |
                        1 << 27 | 1 << 26 | 1 << 25 | 1 << 24);
      /* disable most machine checks */
      cr_parms.orvals[14] = 0;
      cr_parms.andvals[14] = ~(1 << 28 | 1 << 27 | 1 << 26 |
                         1 << 25 | 1 << 24);

      smp_ctl_bit_callback(&cr_parms);

      return 0;
}

void __cpu_die(unsigned int cpu)
{
      /* Wait until target cpu is down */
      while (!smp_cpu_not_running(cpu))
            cpu_relax();
      printk("Processor %d spun down\n", cpu);
}

void cpu_die(void)
{
      idle_task_exit();
      signal_processor(smp_processor_id(), sigp_stop);
      BUG();
      for (;;);
}

#endif /* CONFIG_HOTPLUG_CPU */

/*
 *    Cycle through the processors and setup structures.
 */

void __init smp_prepare_cpus(unsigned int max_cpus)
{
      unsigned long stack;
      unsigned int cpu;
      int i;

      /* request the 0x1201 emergency signal external interrupt */
      if (register_external_interrupt(0x1201, do_ext_call_interrupt) != 0)
            panic("Couldn't request external interrupt 0x1201");
      memset(lowcore_ptr, 0, sizeof(lowcore_ptr));
      /*
       *  Initialize prefix pages and stacks for all possible cpus
       */
      print_cpu_info(&S390_lowcore.cpu_data);

      for_each_possible_cpu(i) {
            lowcore_ptr[i] = (struct _lowcore *)
                  __get_free_pages(GFP_KERNEL | GFP_DMA,
                               sizeof(void*) == 8 ? 1 : 0);
            stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
            if (!lowcore_ptr[i] || !stack)
                  panic("smp_boot_cpus failed to allocate memory\n");

            *(lowcore_ptr[i]) = S390_lowcore;
            lowcore_ptr[i]->async_stack = stack + ASYNC_SIZE;
            stack = __get_free_pages(GFP_KERNEL, 0);
            if (!stack)
                  panic("smp_boot_cpus failed to allocate memory\n");
            lowcore_ptr[i]->panic_stack = stack + PAGE_SIZE;
#ifndef CONFIG_64BIT
            if (MACHINE_HAS_IEEE) {
                  lowcore_ptr[i]->extended_save_area_addr =
                        (__u32) __get_free_pages(GFP_KERNEL, 0);
                  if (!lowcore_ptr[i]->extended_save_area_addr)
                        panic("smp_boot_cpus failed to "
                              "allocate memory\n");
            }
#endif
      }
#ifndef CONFIG_64BIT
      if (MACHINE_HAS_IEEE)
            ctl_set_bit(14, 29); /* enable extended save area */
#endif
      set_prefix((u32)(unsigned long) lowcore_ptr[smp_processor_id()]);

      for_each_possible_cpu(cpu)
            if (cpu != smp_processor_id())
                  smp_create_idle(cpu);
}

void __init smp_prepare_boot_cpu(void)
{
      BUG_ON(smp_processor_id() != 0);

      cpu_set(0, cpu_online_map);
      S390_lowcore.percpu_offset = __per_cpu_offset[0];
      current_set[0] = current;
      spin_lock_init(&(&__get_cpu_var(s390_idle))->lock);
}

void __init smp_cpus_done(unsigned int max_cpus)
{
      cpu_present_map = cpu_possible_map;
}

/*
 * the frequency of the profiling timer can be changed
 * by writing a multiplier value into /proc/profile.
 *
 * usually you want to run this on all CPUs ;)
 */
int setup_profiling_timer(unsigned int multiplier)
{
      return 0;
}

static DEFINE_PER_CPU(struct cpu, cpu_devices);

static ssize_t show_capability(struct sys_device *dev, char *buf)
{
      unsigned int capability;
      int rc;

      rc = get_cpu_capability(&capability);
      if (rc)
            return rc;
      return sprintf(buf, "%u\n", capability);
}
static SYSDEV_ATTR(capability, 0444, show_capability, NULL);

static ssize_t show_idle_count(struct sys_device *dev, char *buf)
{
      struct s390_idle_data *idle;
      unsigned long long idle_count;

      idle = &per_cpu(s390_idle, dev->id);
      spin_lock_irq(&idle->lock);
      idle_count = idle->idle_count;
      spin_unlock_irq(&idle->lock);
      return sprintf(buf, "%llu\n", idle_count);
}
static SYSDEV_ATTR(idle_count, 0444, show_idle_count, NULL);

static ssize_t show_idle_time(struct sys_device *dev, char *buf)
{
      struct s390_idle_data *idle;
      unsigned long long new_time;

      idle = &per_cpu(s390_idle, dev->id);
      spin_lock_irq(&idle->lock);
      if (idle->in_idle) {
            new_time = get_clock();
            idle->idle_time += new_time - idle->idle_enter;
            idle->idle_enter = new_time;
      }
      new_time = idle->idle_time;
      spin_unlock_irq(&idle->lock);
      return sprintf(buf, "%llu\n", new_time >> 12);
}
static SYSDEV_ATTR(idle_time_us, 0444, show_idle_time, NULL);

static struct attribute *cpu_attrs[] = {
      &attr_capability.attr,
      &attr_idle_count.attr,
      &attr_idle_time_us.attr,
      NULL,
};

static struct attribute_group cpu_attr_group = {
      .attrs = cpu_attrs,
};

static int __cpuinit smp_cpu_notify(struct notifier_block *self,
                            unsigned long action, void *hcpu)
{
      unsigned int cpu = (unsigned int)(long)hcpu;
      struct cpu *c = &per_cpu(cpu_devices, cpu);
      struct sys_device *s = &c->sysdev;
      struct s390_idle_data *idle;

      switch (action) {
      case CPU_ONLINE:
      case CPU_ONLINE_FROZEN:
            idle = &per_cpu(s390_idle, cpu);
            spin_lock_irq(&idle->lock);
            idle->idle_enter = 0;
            idle->idle_time = 0;
            idle->idle_count = 0;
            spin_unlock_irq(&idle->lock);
            if (sysfs_create_group(&s->kobj, &cpu_attr_group))
                  return NOTIFY_BAD;
            break;
      case CPU_DEAD:
      case CPU_DEAD_FROZEN:
            sysfs_remove_group(&s->kobj, &cpu_attr_group);
            break;
      }
      return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata smp_cpu_nb = {
      .notifier_call = smp_cpu_notify,
};

static int __init topology_init(void)
{
      int cpu;
      int rc;

      register_cpu_notifier(&smp_cpu_nb);

      for_each_possible_cpu(cpu) {
            struct cpu *c = &per_cpu(cpu_devices, cpu);
            struct sys_device *s = &c->sysdev;

            c->hotpluggable = 1;
            register_cpu(c, cpu);
            if (!cpu_online(cpu))
                  continue;
            s = &c->sysdev;
            rc = sysfs_create_group(&s->kobj, &cpu_attr_group);
            if (rc)
                  return rc;
      }
      return 0;
}
subsys_initcall(topology_init);

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