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smp.c

/*
 *  linux/arch/arm/kernel/smp.c
 *
 *  Copyright (C) 2002 ARM Limited, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/cache.h>
#include <linux/profile.h>
#include <linux/errno.h>
#include <linux/ftrace.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/seq_file.h>
#include <linux/irq.h>
#include <linux/percpu.h>
#include <linux/clockchips.h>
#include <linux/completion.h>

#include <asm/atomic.h>
#include <asm/cacheflush.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/ptrace.h>
#include <asm/localtimer.h>

/*
 * as from 2.5, kernels no longer have an init_tasks structure
 * so we need some other way of telling a new secondary core
 * where to place its SVC stack
 */
struct secondary_data secondary_data;

enum ipi_msg_type {
      IPI_TIMER = 2,
      IPI_RESCHEDULE,
      IPI_CALL_FUNC,
      IPI_CALL_FUNC_SINGLE,
      IPI_CPU_STOP,
};

int __cpuinit __cpu_up(unsigned int cpu)
{
      struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);
      struct task_struct *idle = ci->idle;
      pgd_t *pgd;
      int ret;

      /*
       * Spawn a new process manually, if not already done.
       * Grab a pointer to its task struct so we can mess with it
       */
      if (!idle) {
            idle = fork_idle(cpu);
            if (IS_ERR(idle)) {
                  printk(KERN_ERR "CPU%u: fork() failed\n", cpu);
                  return PTR_ERR(idle);
            }
            ci->idle = idle;
      } else {
            /*
             * Since this idle thread is being re-used, call
             * init_idle() to reinitialize the thread structure.
             */
            init_idle(idle, cpu);
      }

      /*
       * Allocate initial page tables to allow the new CPU to
       * enable the MMU safely.  This essentially means a set
       * of our "standard" page tables, with the addition of
       * a 1:1 mapping for the physical address of the kernel.
       */
      pgd = pgd_alloc(&init_mm);
      if (!pgd)
            return -ENOMEM;

      if (PHYS_OFFSET != PAGE_OFFSET) {
#ifndef CONFIG_HOTPLUG_CPU
            identity_mapping_add(pgd, __pa(__init_begin), __pa(__init_end));
#endif
            identity_mapping_add(pgd, __pa(_stext), __pa(_etext));
            identity_mapping_add(pgd, __pa(_sdata), __pa(_edata));
      }

      /*
       * We need to tell the secondary core where to find
       * its stack and the page tables.
       */
      secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
      secondary_data.pgdir = virt_to_phys(pgd);
      __cpuc_flush_dcache_area(&secondary_data, sizeof(secondary_data));
      outer_clean_range(__pa(&secondary_data), __pa(&secondary_data + 1));

      /*
       * Now bring the CPU into our world.
       */
      ret = boot_secondary(cpu, idle);
      if (ret == 0) {
            unsigned long timeout;

            /*
             * CPU was successfully started, wait for it
             * to come online or time out.
             */
            timeout = jiffies + HZ;
            while (time_before(jiffies, timeout)) {
                  if (cpu_online(cpu))
                        break;

                  udelay(10);
                  barrier();
            }

            if (!cpu_online(cpu)) {
                  pr_crit("CPU%u: failed to come online\n", cpu);
                  ret = -EIO;
            }
      } else {
            pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
      }

      secondary_data.stack = NULL;
      secondary_data.pgdir = 0;

      if (PHYS_OFFSET != PAGE_OFFSET) {
#ifndef CONFIG_HOTPLUG_CPU
            identity_mapping_del(pgd, __pa(__init_begin), __pa(__init_end));
#endif
            identity_mapping_del(pgd, __pa(_stext), __pa(_etext));
            identity_mapping_del(pgd, __pa(_sdata), __pa(_edata));
      }

      pgd_free(&init_mm, pgd);

      return ret;
}

#ifdef CONFIG_HOTPLUG_CPU
static void percpu_timer_stop(void);

/*
 * __cpu_disable runs on the processor to be shutdown.
 */
int __cpu_disable(void)
{
      unsigned int cpu = smp_processor_id();
      struct task_struct *p;
      int ret;

      ret = platform_cpu_disable(cpu);
      if (ret)
            return ret;

      /*
       * Take this CPU offline.  Once we clear this, we can't return,
       * and we must not schedule until we're ready to give up the cpu.
       */
      set_cpu_online(cpu, false);

      /*
       * OK - migrate IRQs away from this CPU
       */
      migrate_irqs();

      /*
       * Stop the local timer for this CPU.
       */
      percpu_timer_stop();

      /*
       * Flush user cache and TLB mappings, and then remove this CPU
       * from the vm mask set of all processes.
       */
      flush_cache_all();
      local_flush_tlb_all();

      read_lock(&tasklist_lock);
      for_each_process(p) {
            if (p->mm)
                  cpumask_clear_cpu(cpu, mm_cpumask(p->mm));
      }
      read_unlock(&tasklist_lock);

      return 0;
}

static DECLARE_COMPLETION(cpu_died);

/*
 * called on the thread which is asking for a CPU to be shutdown -
 * waits until shutdown has completed, or it is timed out.
 */
void __cpu_die(unsigned int cpu)
{
      if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) {
            pr_err("CPU%u: cpu didn't die\n", cpu);
            return;
      }
      printk(KERN_NOTICE "CPU%u: shutdown\n", cpu);

      if (!platform_cpu_kill(cpu))
            printk("CPU%u: unable to kill\n", cpu);
}

/*
 * Called from the idle thread for the CPU which has been shutdown.
 *
 * Note that we disable IRQs here, but do not re-enable them
 * before returning to the caller. This is also the behaviour
 * of the other hotplug-cpu capable cores, so presumably coming
 * out of idle fixes this.
 */
void __ref cpu_die(void)
{
      unsigned int cpu = smp_processor_id();

      idle_task_exit();

      local_irq_disable();
      mb();

      /* Tell __cpu_die() that this CPU is now safe to dispose of */
      complete(&cpu_died);

      /*
       * actual CPU shutdown procedure is at least platform (if not
       * CPU) specific.
       */
      platform_cpu_die(cpu);

      /*
       * Do not return to the idle loop - jump back to the secondary
       * cpu initialisation.  There's some initialisation which needs
       * to be repeated to undo the effects of taking the CPU offline.
       */
      __asm__("mov      sp, %0\n"
      "     mov   fp, #0\n"
      "     b     secondary_start_kernel"
            :
            : "r" (task_stack_page(current) + THREAD_SIZE - 8));
}
#endif /* CONFIG_HOTPLUG_CPU */

/*
 * Called by both boot and secondaries to move global data into
 * per-processor storage.
 */
static void __cpuinit smp_store_cpu_info(unsigned int cpuid)
{
      struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);

      cpu_info->loops_per_jiffy = loops_per_jiffy;
}

/*
 * This is the secondary CPU boot entry.  We're using this CPUs
 * idle thread stack, but a set of temporary page tables.
 */
asmlinkage void __cpuinit secondary_start_kernel(void)
{
      struct mm_struct *mm = &init_mm;
      unsigned int cpu = smp_processor_id();

      printk("CPU%u: Booted secondary processor\n", cpu);

      /*
       * All kernel threads share the same mm context; grab a
       * reference and switch to it.
       */
      atomic_inc(&mm->mm_count);
      current->active_mm = mm;
      cpumask_set_cpu(cpu, mm_cpumask(mm));
      cpu_switch_mm(mm->pgd, mm);
      enter_lazy_tlb(mm, current);
      local_flush_tlb_all();

      cpu_init();
      preempt_disable();
      trace_hardirqs_off();

      /*
       * Give the platform a chance to do its own initialisation.
       */
      platform_secondary_init(cpu);

      /*
       * Enable local interrupts.
       */
      notify_cpu_starting(cpu);
      local_irq_enable();
      local_fiq_enable();

      /*
       * Setup the percpu timer for this CPU.
       */
      percpu_timer_setup();

      calibrate_delay();

      smp_store_cpu_info(cpu);

      /*
       * OK, now it's safe to let the boot CPU continue
       */
      set_cpu_online(cpu, true);

      /*
       * OK, it's off to the idle thread for us
       */
      cpu_idle();
}

void __init smp_cpus_done(unsigned int max_cpus)
{
      int cpu;
      unsigned long bogosum = 0;

      for_each_online_cpu(cpu)
            bogosum += per_cpu(cpu_data, cpu).loops_per_jiffy;

      printk(KERN_INFO "SMP: Total of %d processors activated "
             "(%lu.%02lu BogoMIPS).\n",
             num_online_cpus(),
             bogosum / (500000/HZ),
             (bogosum / (5000/HZ)) % 100);
}

void __init smp_prepare_boot_cpu(void)
{
      unsigned int cpu = smp_processor_id();

      per_cpu(cpu_data, cpu).idle = current;
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
      unsigned int ncores = num_possible_cpus();

      smp_store_cpu_info(smp_processor_id());

      /*
       * are we trying to boot more cores than exist?
       */
      if (max_cpus > ncores)
            max_cpus = ncores;

      if (max_cpus > 1) {
            /*
             * Enable the local timer or broadcast device for the
             * boot CPU, but only if we have more than one CPU.
             */
            percpu_timer_setup();

            /*
             * Initialise the SCU if there are more than one CPU
             * and let them know where to start.
             */
            platform_smp_prepare_cpus(max_cpus);
      }
}

void arch_send_call_function_ipi_mask(const struct cpumask *mask)
{
      smp_cross_call(mask, IPI_CALL_FUNC);
}

void arch_send_call_function_single_ipi(int cpu)
{
      smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
}

static const char *ipi_types[NR_IPI] = {
#define S(x,s)    [x - IPI_TIMER] = s
      S(IPI_TIMER, "Timer broadcast interrupts"),
      S(IPI_RESCHEDULE, "Rescheduling interrupts"),
      S(IPI_CALL_FUNC, "Function call interrupts"),
      S(IPI_CALL_FUNC_SINGLE, "Single function call interrupts"),
      S(IPI_CPU_STOP, "CPU stop interrupts"),
};

void show_ipi_list(struct seq_file *p, int prec)
{
      unsigned int cpu, i;

      for (i = 0; i < NR_IPI; i++) {
            seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);

            for_each_present_cpu(cpu)
                  seq_printf(p, "%10u ",
                           __get_irq_stat(cpu, ipi_irqs[i]));

            seq_printf(p, " %s\n", ipi_types[i]);
      }
}

u64 smp_irq_stat_cpu(unsigned int cpu)
{
      u64 sum = 0;
      int i;

      for (i = 0; i < NR_IPI; i++)
            sum += __get_irq_stat(cpu, ipi_irqs[i]);

#ifdef CONFIG_LOCAL_TIMERS
      sum += __get_irq_stat(cpu, local_timer_irqs);
#endif

      return sum;
}

/*
 * Timer (local or broadcast) support
 */
static DEFINE_PER_CPU(struct clock_event_device, percpu_clockevent);

static void ipi_timer(void)
{
      struct clock_event_device *evt = &__get_cpu_var(percpu_clockevent);
      irq_enter();
      evt->event_handler(evt);
      irq_exit();
}

#ifdef CONFIG_LOCAL_TIMERS
asmlinkage void __exception_irq_entry do_local_timer(struct pt_regs *regs)
{
      struct pt_regs *old_regs = set_irq_regs(regs);
      int cpu = smp_processor_id();

      if (local_timer_ack()) {
            __inc_irq_stat(cpu, local_timer_irqs);
            ipi_timer();
      }

      set_irq_regs(old_regs);
}

void show_local_irqs(struct seq_file *p, int prec)
{
      unsigned int cpu;

      seq_printf(p, "%*s: ", prec, "LOC");

      for_each_present_cpu(cpu)
            seq_printf(p, "%10u ", __get_irq_stat(cpu, local_timer_irqs));

      seq_printf(p, " Local timer interrupts\n");
}
#endif

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
static void smp_timer_broadcast(const struct cpumask *mask)
{
      smp_cross_call(mask, IPI_TIMER);
}
#else
#define smp_timer_broadcast   NULL
#endif

#ifndef CONFIG_LOCAL_TIMERS
static void broadcast_timer_set_mode(enum clock_event_mode mode,
      struct clock_event_device *evt)
{
}

static void local_timer_setup(struct clock_event_device *evt)
{
      evt->name   = "dummy_timer";
      evt->features     = CLOCK_EVT_FEAT_ONESHOT |
                    CLOCK_EVT_FEAT_PERIODIC |
                    CLOCK_EVT_FEAT_DUMMY;
      evt->rating = 400;
      evt->mult   = 1;
      evt->set_mode     = broadcast_timer_set_mode;

      clockevents_register_device(evt);
}
#endif

void __cpuinit percpu_timer_setup(void)
{
      unsigned int cpu = smp_processor_id();
      struct clock_event_device *evt = &per_cpu(percpu_clockevent, cpu);

      evt->cpumask = cpumask_of(cpu);
      evt->broadcast = smp_timer_broadcast;

      local_timer_setup(evt);
}

#ifdef CONFIG_HOTPLUG_CPU
/*
 * The generic clock events code purposely does not stop the local timer
 * on CPU_DEAD/CPU_DEAD_FROZEN hotplug events, so we have to do it
 * manually here.
 */
static void percpu_timer_stop(void)
{
      unsigned int cpu = smp_processor_id();
      struct clock_event_device *evt = &per_cpu(percpu_clockevent, cpu);

      evt->set_mode(CLOCK_EVT_MODE_UNUSED, evt);
}
#endif

static DEFINE_SPINLOCK(stop_lock);

/*
 * ipi_cpu_stop - handle IPI from smp_send_stop()
 */
static void ipi_cpu_stop(unsigned int cpu)
{
      if (system_state == SYSTEM_BOOTING ||
          system_state == SYSTEM_RUNNING) {
            spin_lock(&stop_lock);
            printk(KERN_CRIT "CPU%u: stopping\n", cpu);
            dump_stack();
            spin_unlock(&stop_lock);
      }

      set_cpu_online(cpu, false);

      local_fiq_disable();
      local_irq_disable();

      while (1)
            cpu_relax();
}

/*
 * Main handler for inter-processor interrupts
 */
asmlinkage void __exception_irq_entry do_IPI(int ipinr, struct pt_regs *regs)
{
      unsigned int cpu = smp_processor_id();
      struct pt_regs *old_regs = set_irq_regs(regs);

      if (ipinr >= IPI_TIMER && ipinr < IPI_TIMER + NR_IPI)
            __inc_irq_stat(cpu, ipi_irqs[ipinr - IPI_TIMER]);

      switch (ipinr) {
      case IPI_TIMER:
            ipi_timer();
            break;

      case IPI_RESCHEDULE:
            /*
             * nothing more to do - eveything is
             * done on the interrupt return path
             */
            break;

      case IPI_CALL_FUNC:
            generic_smp_call_function_interrupt();
            break;

      case IPI_CALL_FUNC_SINGLE:
            generic_smp_call_function_single_interrupt();
            break;

      case IPI_CPU_STOP:
            ipi_cpu_stop(cpu);
            break;

      default:
            printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",
                   cpu, ipinr);
            break;
      }
      set_irq_regs(old_regs);
}

void smp_send_reschedule(int cpu)
{
      smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}

void smp_send_stop(void)
{
      unsigned long timeout;

      if (num_online_cpus() > 1) {
            cpumask_t mask = cpu_online_map;
            cpu_clear(smp_processor_id(), mask);

            smp_cross_call(&mask, IPI_CPU_STOP);
      }

      /* Wait up to one second for other CPUs to stop */
      timeout = USEC_PER_SEC;
      while (num_online_cpus() > 1 && timeout--)
            udelay(1);

      if (num_online_cpus() > 1)
            pr_warning("SMP: failed to stop secondary CPUs\n");
}

/*
 * not supported here
 */
int setup_profiling_timer(unsigned int multiplier)
{
      return -EINVAL;
}

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