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 brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =
  19    { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = 0 } };
  20
  21 struct br_wrlock __br_write_locks[__BR_IDX_MAX] =
  22    { [0 ... __BR_IDX_MAX-1] = { SPIN_LOCK_UNLOCKED } };
  23
  24 void fastcall __br_write_lock (enum brlock_indices idx)
  25 {
  26         int i;
  27
  28 again:
  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
  39 void fastcall __br_write_unlock (enum brlock_indices idx)
  40 {
  41         spin_unlock(&__br_write_locks[idx].lock);
  42 }
  43
  44 #endif /* CONFIG_SMP */