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spinlock.c

/*
 *  arch/s390/lib/spinlock.c
 *    Out of line spinlock code.
 *
 *    Copyright (C) IBM Corp. 2004, 2006
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
 */

#include <linux/types.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <asm/io.h>

int spin_retry = 1000;

/**
 * spin_retry= parameter
 */
static int __init spin_retry_setup(char *str)
{
      spin_retry = simple_strtoul(str, &str, 0);
      return 1;
}
__setup("spin_retry=", spin_retry_setup);

static inline void _raw_yield(void)
{
      if (MACHINE_HAS_DIAG44)
            asm volatile("diag 0,0,0x44");
}

static inline void _raw_yield_cpu(int cpu)
{
      if (MACHINE_HAS_DIAG9C)
            asm volatile("diag %0,0,0x9c"
                       : : "d" (__cpu_logical_map[cpu]));
      else
            _raw_yield();
}

void _raw_spin_lock_wait(raw_spinlock_t *lp)
{
      int count = spin_retry;
      unsigned int cpu = ~smp_processor_id();

      while (1) {
            if (count-- <= 0) {
                  unsigned int owner = lp->owner_cpu;
                  if (owner != 0)
                        _raw_yield_cpu(~owner);
                  count = spin_retry;
            }
            if (__raw_spin_is_locked(lp))
                  continue;
            if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
                  return;
      }
}
EXPORT_SYMBOL(_raw_spin_lock_wait);

void _raw_spin_lock_wait_flags(raw_spinlock_t *lp, unsigned long flags)
{
      int count = spin_retry;
      unsigned int cpu = ~smp_processor_id();

      local_irq_restore(flags);
      while (1) {
            if (count-- <= 0) {
                  unsigned int owner = lp->owner_cpu;
                  if (owner != 0)
                        _raw_yield_cpu(~owner);
                  count = spin_retry;
            }
            if (__raw_spin_is_locked(lp))
                  continue;
            local_irq_disable();
            if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
                  return;
            local_irq_restore(flags);
      }
}
EXPORT_SYMBOL(_raw_spin_lock_wait_flags);

int _raw_spin_trylock_retry(raw_spinlock_t *lp)
{
      unsigned int cpu = ~smp_processor_id();
      int count;

      for (count = spin_retry; count > 0; count--) {
            if (__raw_spin_is_locked(lp))
                  continue;
            if (_raw_compare_and_swap(&lp->owner_cpu, 0, cpu) == 0)
                  return 1;
      }
      return 0;
}
EXPORT_SYMBOL(_raw_spin_trylock_retry);

void _raw_spin_relax(raw_spinlock_t *lock)
{
      unsigned int cpu = lock->owner_cpu;
      if (cpu != 0)
            _raw_yield_cpu(~cpu);
}
EXPORT_SYMBOL(_raw_spin_relax);

void _raw_read_lock_wait(raw_rwlock_t *rw)
{
      unsigned int old;
      int count = spin_retry;

      while (1) {
            if (count-- <= 0) {
                  _raw_yield();
                  count = spin_retry;
            }
            if (!__raw_read_can_lock(rw))
                  continue;
            old = rw->lock & 0x7fffffffU;
            if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
                  return;
      }
}
EXPORT_SYMBOL(_raw_read_lock_wait);

int _raw_read_trylock_retry(raw_rwlock_t *rw)
{
      unsigned int old;
      int count = spin_retry;

      while (count-- > 0) {
            if (!__raw_read_can_lock(rw))
                  continue;
            old = rw->lock & 0x7fffffffU;
            if (_raw_compare_and_swap(&rw->lock, old, old + 1) == old)
                  return 1;
      }
      return 0;
}
EXPORT_SYMBOL(_raw_read_trylock_retry);

void _raw_write_lock_wait(raw_rwlock_t *rw)
{
      int count = spin_retry;

      while (1) {
            if (count-- <= 0) {
                  _raw_yield();
                  count = spin_retry;
            }
            if (!__raw_write_can_lock(rw))
                  continue;
            if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
                  return;
      }
}
EXPORT_SYMBOL(_raw_write_lock_wait);

int _raw_write_trylock_retry(raw_rwlock_t *rw)
{
      int count = spin_retry;

      while (count-- > 0) {
            if (!__raw_write_can_lock(rw))
                  continue;
            if (_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0)
                  return 1;
      }
      return 0;
}
EXPORT_SYMBOL(_raw_write_trylock_retry);

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