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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 */