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 
__br_write_lock(enum brlock_indices idx)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 
__br_write_unlock(enum brlock_indices idx)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 */
45