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smp.c

/*
 * SMP Support
 *
 * Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
 * Copyright (C) 1999, 2001, 2003 David Mosberger-Tang <davidm@hpl.hp.com>
 *
 * Lots of stuff stolen from arch/alpha/kernel/smp.c
 *
 * 01/05/16 Rohit Seth <rohit.seth@intel.com>  IA64-SMP functions. Reorganized
 * the existing code (on the lines of x86 port).
 * 00/09/11 David Mosberger <davidm@hpl.hp.com> Do loops_per_jiffy
 * calibration on each CPU.
 * 00/08/23 Asit Mallick <asit.k.mallick@intel.com> fixed logical processor id
 * 00/03/31 Rohit Seth <rohit.seth@intel.com>   Fixes for Bootstrap Processor
 * & cpu_online_map now gets done here (instead of setup.c)
 * 99/10/05 davidm      Update to bring it in sync with new command-line processing
 *  scheme.
 * 10/13/00 Goutham Rao <goutham.rao@intel.com> Updated smp_call_function and
 *          smp_call_function_single to resend IPI on timeouts
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/cache.h>
#include <linux/delay.h>
#include <linux/efi.h>
#include <linux/bitops.h>
#include <linux/kexec.h>

#include <asm/atomic.h>
#include <asm/current.h>
#include <asm/delay.h>
#include <asm/machvec.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/sal.h>
#include <asm/system.h>
#include <asm/tlbflush.h>
#include <asm/unistd.h>
#include <asm/mca.h>

/*
 * Note: alignment of 4 entries/cacheline was empirically determined
 * to be a good tradeoff between hot cachelines & spreading the array
 * across too many cacheline.
 */
static struct local_tlb_flush_counts {
      unsigned int count;
} __attribute__((__aligned__(32))) local_tlb_flush_counts[NR_CPUS];

static DEFINE_PER_CPU(unsigned int, shadow_flush_counts[NR_CPUS]) ____cacheline_aligned;


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

struct call_data_struct {
      void (*func) (void *info);
      void *info;
      long wait;
      atomic_t started;
      atomic_t finished;
};

static volatile struct call_data_struct *call_data;

#define IPI_CALL_FUNC         0
#define IPI_CPU_STOP          1
#define IPI_KDUMP_CPU_STOP    3

/* This needs to be cacheline aligned because it is written to by *other* CPUs.  */
static DEFINE_PER_CPU_SHARED_ALIGNED(u64, ipi_operation);

extern void cpu_halt (void);

void
lock_ipi_calllock(void)
{
      spin_lock_irq(&call_lock);
}

void
unlock_ipi_calllock(void)
{
      spin_unlock_irq(&call_lock);
}

static void
stop_this_cpu (void)
{
      /*
       * Remove this CPU:
       */
      cpu_clear(smp_processor_id(), cpu_online_map);
      max_xtp();
      local_irq_disable();
      cpu_halt();
}

void
cpu_die(void)
{
      max_xtp();
      local_irq_disable();
      cpu_halt();
      /* Should never be here */
      BUG();
      for (;;);
}

irqreturn_t
handle_IPI (int irq, void *dev_id)
{
      int this_cpu = get_cpu();
      unsigned long *pending_ipis = &__ia64_per_cpu_var(ipi_operation);
      unsigned long ops;

      mb(); /* Order interrupt and bit testing. */
      while ((ops = xchg(pending_ipis, 0)) != 0) {
            mb(); /* Order bit clearing and data access. */
            do {
                  unsigned long which;

                  which = ffz(~ops);
                  ops &= ~(1 << which);

                  switch (which) {
                        case IPI_CALL_FUNC:
                        {
                              struct call_data_struct *data;
                              void (*func)(void *info);
                              void *info;
                              int wait;

                              /* release the 'pointer lock' */
                              data = (struct call_data_struct *) call_data;
                              func = data->func;
                              info = data->info;
                              wait = data->wait;

                              mb();
                              atomic_inc(&data->started);
                              /*
                               * At this point the structure may be gone unless
                               * wait is true.
                               */
                              (*func)(info);

                              /* Notify the sending CPU that the task is done.  */
                              mb();
                              if (wait)
                                    atomic_inc(&data->finished);
                        }
                        break;

                        case IPI_CPU_STOP:
                        stop_this_cpu();
                        break;
#ifdef CONFIG_KEXEC
                        case IPI_KDUMP_CPU_STOP:
                        unw_init_running(kdump_cpu_freeze, NULL);
                        break;
#endif
                        default:
                        printk(KERN_CRIT "Unknown IPI on CPU %d: %lu\n", this_cpu, which);
                        break;
                  }
            } while (ops);
            mb(); /* Order data access and bit testing. */
      }
      put_cpu();
      return IRQ_HANDLED;
}

/*
 * Called with preemption disabled.
 */
static inline void
send_IPI_single (int dest_cpu, int op)
{
      set_bit(op, &per_cpu(ipi_operation, dest_cpu));
      platform_send_ipi(dest_cpu, IA64_IPI_VECTOR, IA64_IPI_DM_INT, 0);
}

/*
 * Called with preemption disabled.
 */
static inline void
send_IPI_allbutself (int op)
{
      unsigned int i;

      for_each_online_cpu(i) {
            if (i != smp_processor_id())
                  send_IPI_single(i, op);
      }
}

/*
 * Called with preemption disabled.
 */
static inline void
send_IPI_all (int op)
{
      int i;

      for_each_online_cpu(i) {
            send_IPI_single(i, op);
      }
}

/*
 * Called with preemption disabled.
 */
static inline void
send_IPI_self (int op)
{
      send_IPI_single(smp_processor_id(), op);
}

#ifdef CONFIG_KEXEC
void
kdump_smp_send_stop(void)
{
      send_IPI_allbutself(IPI_KDUMP_CPU_STOP);
}

void
kdump_smp_send_init(void)
{
      unsigned int cpu, self_cpu;
      self_cpu = smp_processor_id();
      for_each_online_cpu(cpu) {
            if (cpu != self_cpu) {
                  if(kdump_status[cpu] == 0)
                        platform_send_ipi(cpu, 0, IA64_IPI_DM_INIT, 0);
            }
      }
}
#endif
/*
 * Called with preemption disabled.
 */
void
smp_send_reschedule (int cpu)
{
      platform_send_ipi(cpu, IA64_IPI_RESCHEDULE, IA64_IPI_DM_INT, 0);
}

/*
 * Called with preemption disabled.
 */
static void
smp_send_local_flush_tlb (int cpu)
{
      platform_send_ipi(cpu, IA64_IPI_LOCAL_TLB_FLUSH, IA64_IPI_DM_INT, 0);
}

void
smp_local_flush_tlb(void)
{
      /*
       * Use atomic ops. Otherwise, the load/increment/store sequence from
       * a "++" operation can have the line stolen between the load & store.
       * The overhead of the atomic op in negligible in this case & offers
       * significant benefit for the brief periods where lots of cpus
       * are simultaneously flushing TLBs.
       */
      ia64_fetchadd(1, &local_tlb_flush_counts[smp_processor_id()].count, acq);
      local_flush_tlb_all();
}

#define FLUSH_DELAY     5 /* Usec backoff to eliminate excessive cacheline bouncing */

void
smp_flush_tlb_cpumask(cpumask_t xcpumask)
{
      unsigned int *counts = __ia64_per_cpu_var(shadow_flush_counts);
      cpumask_t cpumask = xcpumask;
      int mycpu, cpu, flush_mycpu = 0;

      preempt_disable();
      mycpu = smp_processor_id();

      for_each_cpu_mask(cpu, cpumask)
            counts[cpu] = local_tlb_flush_counts[cpu].count;

      mb();
      for_each_cpu_mask(cpu, cpumask) {
            if (cpu == mycpu)
                  flush_mycpu = 1;
            else
                  smp_send_local_flush_tlb(cpu);
      }

      if (flush_mycpu)
            smp_local_flush_tlb();

      for_each_cpu_mask(cpu, cpumask)
            while(counts[cpu] == local_tlb_flush_counts[cpu].count)
                  udelay(FLUSH_DELAY);

      preempt_enable();
}

void
smp_flush_tlb_all (void)
{
      on_each_cpu((void (*)(void *))local_flush_tlb_all, NULL, 1, 1);
}

void
smp_flush_tlb_mm (struct mm_struct *mm)
{
      preempt_disable();
      /* this happens for the common case of a single-threaded fork():  */
      if (likely(mm == current->active_mm && atomic_read(&mm->mm_users) == 1))
      {
            local_finish_flush_tlb_mm(mm);
            preempt_enable();
            return;
      }

      preempt_enable();
      /*
       * We could optimize this further by using mm->cpu_vm_mask to track which CPUs
       * have been running in the address space.  It's not clear that this is worth the
       * trouble though: to avoid races, we have to raise the IPI on the target CPU
       * anyhow, and once a CPU is interrupted, the cost of local_flush_tlb_all() is
       * rather trivial.
       */
      on_each_cpu((void (*)(void *))local_finish_flush_tlb_mm, mm, 1, 1);
}

/*
 * Run a function on a specific CPU
 *  <func>  The function to run. This must be fast and non-blocking.
 *  <info>  An arbitrary pointer to pass to the function.
 *  <nonatomic>   Currently unused.
 *  <wait>  If true, wait until function has completed on other CPUs.
 *  [RETURNS]   0 on success, else a negative status code.
 *
 * Does not return until the remote CPU is nearly ready to execute <func>
 * or is or has executed.
 */

int
smp_call_function_single (int cpuid, void (*func) (void *info), void *info, int nonatomic,
                    int wait)
{
      struct call_data_struct data;
      int cpus = 1;
      int me = get_cpu(); /* prevent preemption and reschedule on another processor */

      if (cpuid == me) {
            local_irq_disable();
            func(info);
            local_irq_enable();
            put_cpu();
            return 0;
      }

      data.func = func;
      data.info = info;
      atomic_set(&data.started, 0);
      data.wait = wait;
      if (wait)
            atomic_set(&data.finished, 0);

      spin_lock_bh(&call_lock);

      call_data = &data;
      mb(); /* ensure store to call_data precedes setting of IPI_CALL_FUNC */
      send_IPI_single(cpuid, IPI_CALL_FUNC);

      /* Wait for response */
      while (atomic_read(&data.started) != cpus)
            cpu_relax();

      if (wait)
            while (atomic_read(&data.finished) != cpus)
                  cpu_relax();
      call_data = NULL;

      spin_unlock_bh(&call_lock);
      put_cpu();
      return 0;
}
EXPORT_SYMBOL(smp_call_function_single);

/*
 * this function sends a 'generic call function' IPI to all other CPUs
 * in the system.
 */

/*
 *  [SUMMARY]     Run a function on all other CPUs.
 *  <func>  The function to run. This must be fast and non-blocking.
 *  <info>  An arbitrary pointer to pass to the function.
 *  <nonatomic>   currently unused.
 *  <wait>  If true, wait (atomically) until function has completed on other CPUs.
 *  [RETURNS]   0 on success, else a negative status code.
 *
 * Does not return until remote CPUs are nearly ready to execute <func> or are or have
 * executed.
 *
 * You must not call this function with disabled interrupts or from a
 * hardware interrupt handler or from a bottom half handler.
 */
int
smp_call_function (void (*func) (void *info), void *info, int nonatomic, int wait)
{
      struct call_data_struct data;
      int cpus;

      spin_lock(&call_lock);
      cpus = num_online_cpus() - 1;
      if (!cpus) {
            spin_unlock(&call_lock);
            return 0;
      }

      /* Can deadlock when called with interrupts disabled */
      WARN_ON(irqs_disabled());

      data.func = func;
      data.info = info;
      atomic_set(&data.started, 0);
      data.wait = wait;
      if (wait)
            atomic_set(&data.finished, 0);

      call_data = &data;
      mb(); /* ensure store to call_data precedes setting of IPI_CALL_FUNC */
      send_IPI_allbutself(IPI_CALL_FUNC);

      /* Wait for response */
      while (atomic_read(&data.started) != cpus)
            cpu_relax();

      if (wait)
            while (atomic_read(&data.finished) != cpus)
                  cpu_relax();
      call_data = NULL;

      spin_unlock(&call_lock);
      return 0;
}
EXPORT_SYMBOL(smp_call_function);

/*
 * this function calls the 'stop' function on all other CPUs in the system.
 */
void
smp_send_stop (void)
{
      send_IPI_allbutself(IPI_CPU_STOP);
}

int
setup_profiling_timer (unsigned int multiplier)
{
      return -EINVAL;
}

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