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
  20 brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =
  21    { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = RW_LOCK_UNLOCKED } };
  22
  23 void __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[idx] + cpu_logical_map(i));
  29 }
  30
  31 void __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[idx] + cpu_logical_map(i));
  37 }
  38
  39 #else /* ! __BRLOCK_USE_ATOMICS */
  40
  41 brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =
  42    { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = 0 } };
  43
  44 struct br_wrlock __br_write_locks[__BR_IDX_MAX] =
  45    { [0 ... __BR_IDX_MAX-1] = { SPIN_LOCK_UNLOCKED } };
  46
  47 void __br_write_lock (enum brlock_indices idx)
  48 {
  49         int i;
  50
  51         spin_lock(&__br_write_locks[idx].lock);
  52 again:
  53         for (i = 0; i < smp_num_cpus; i++)
  54                 if (__brlock_array[cpu_logical_map(i)][idx] != 0)
  55                         goto again;
  56 }
  57
  58 void __br_write_unlock (enum brlock_indices idx)
  59 {
  60         spin_unlock(&__br_write_locks[idx].lock);
  61 }
  62
  63 #endif /* __BRLOCK_USE_ATOMICS */
  64
  65 #endif /* CONFIG_SMP */