linux-old/lib/brlock.c
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   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
  18brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =
  19   { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = 0 } };
  20
  21struct br_wrlock __br_write_locks[__BR_IDX_MAX] =
  22   { [0 ... __BR_IDX_MAX-1] = { SPIN_LOCK_UNLOCKED } };
  23
  24void fastcall __br_write_lock (enum brlock_indices idx)
  25{
  26        int i;
  27
  28again:
  29        spin_lock(&__br_write_locks[idx].lock);
  30        for (i = 0; i < smp_num_cpus; i++)
  31                if (__brlock_array[cpu_logical_map(i)][idx] != 0) {
  32                        spin_unlock(&__br_write_locks[idx].lock);
  33                        barrier();
  34                        cpu_relax();
  35                        goto again;
  36                }
  37}
  38
  39void fastcall __br_write_unlock (enum brlock_indices idx)
  40{
  41        spin_unlock(&__br_write_locks[idx].lock);
  42}
  43
  44#endif /* CONFIG_SMP */
  45
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