LXR linux-old/lib/brlock.c

   1/*
   2 *
   3 * linux/lib/brlock.c
   4 *
   5 * 'Big Reader' read-write spinlocks.  See linux/brlock.h for details.
   6 *
   7 * Copyright 2000, Ingo Molnar <mingo@redhat.com>
   8 * Copyright 2000, David S. Miller <davem@redhat.com>
   9 */
  10
  11#include <linux/config.h>
  12
  13#ifdef CONFIG_SMP
  14
  15#include <linux/sched.h>
  16#include <linux/brlock.h>
  17
  18#ifdef __BRLOCK_USE_ATOMICS
  19
  20brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =
  21   { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = RW_LOCK_UNLOCKED } };
  22
  23void __br_write_lock (enum brlock_indices idx)
  24{
  25        int i;
  26
  27        for (i = 0; i < smp_num_cpus; i++)
  28                write_lock(&__brlock_array[cpu_logical_map(i)][idx]);
  29}
  30
  31void __br_write_unlock (enum brlock_indices idx)
  32{
  33        int i;
  34
  35        for (i = 0; i < smp_num_cpus; i++)
  36                write_unlock(&__brlock_array[cpu_logical_map(i)][idx]);
  37}
  38
  39#else /* ! __BRLOCK_USE_ATOMICS */
  40
  41brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =
  42   { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = 0 } };
  43
  44struct br_wrlock __br_write_locks[__BR_IDX_MAX] =
  45   { [0 ... __BR_IDX_MAX-1] = { SPIN_LOCK_UNLOCKED } };
  46
  47void __br_write_lock (enum brlock_indices idx)
  48{
  49        int i;
  50
  51again:
  52        spin_lock(&__br_write_locks[idx].lock);
  53        for (i = 0; i < smp_num_cpus; i++)
  54                if (__brlock_array[cpu_logical_map(i)][idx] != 0) {
  55                        spin_unlock(&__br_write_locks[idx].lock);
  56                        barrier();
  57                        cpu_relax();
  58                        goto again;
  59                }
  60}
  61
  62void __br_write_unlock (enum brlock_indices idx)
  63{
  64        spin_unlock(&__br_write_locks[idx].lock);
  65}
  66
  67#endif /* __BRLOCK_USE_ATOMICS */
  68
  69#endif /* CONFIG_SMP */
  70