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/*

 *

 * linux/lib/brlock.c

 *

 * 'Big Reader' read-write spinlocks.  See linux/brlock.h for details.

 *

 * Copyright 2000, Ingo Molnar <mingo@redhat.com>

 * Copyright 2000, David S. Miller <davem@redhat.com>

 */

#include <linux/config.h>

#ifdef CONFIG_SMP

#include <linux/sched.h>

#include <linux/brlock.h>

#ifdef __BRLOCK_USE_ATOMICS

brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =

   { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = RW_LOCK_UNLOCKED } };

void __br_write_lock (enum brlock_indices idx)

{

        int i;

        for (i = 0; i < smp_num_cpus; i++)

                write_lock(&__brlock_array[cpu_logical_map(i)][idx]);

}

void __br_write_unlock (enum brlock_indices idx)

{

        int i;

        for (i = 0; i < smp_num_cpus; i++)

                write_unlock(&__brlock_array[cpu_logical_map(i)][idx]);

}

#else /* ! __BRLOCK_USE_ATOMICS */

brlock_read_lock_t __brlock_array[NR_CPUS][__BR_IDX_MAX] =

   { [0 ... NR_CPUS-1] = { [0 ... __BR_IDX_MAX-1] = 0 } };

struct br_wrlock __br_write_locks[__BR_IDX_MAX] =

   { [0 ... __BR_IDX_MAX-1] = { SPIN_LOCK_UNLOCKED } };

void __br_write_lock (enum brlock_indices idx)

{

        int i;

again:

        spin_lock(&__br_write_locks[idx].lock);

        for (i = 0; i < smp_num_cpus; i++)

                if (__brlock_array[cpu_logical_map(i)][idx] != 0) {

                        spin_unlock(&__br_write_locks[idx].lock);

                        barrier();

                        cpu_relax();

                        goto again;

                }

}

void __br_write_unlock (enum brlock_indices idx)

{

        spin_unlock(&__br_write_locks[idx].lock);

}

#endif /* __BRLOCK_USE_ATOMICS */

#endif /* CONFIG_SMP */