FreeBSD/Linux Kernel Cross Reference
sys/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[cpu_logical_map(i)][idx]);
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[cpu_logical_map(i)][idx]);
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 again:
52 spin_lock(&__br_write_locks[idx].lock);
53 for (i = 0; i < smp_num_cpus; i++)
54 if (__brlock_array[cpu_logical_map(i)][idx] != 0) {
55 spin_unlock(&__br_write_locks[idx].lock);
56 barrier();
57 cpu_relax();
58 goto again;
59 }
60 }
61
62 void __br_write_unlock (enum brlock_indices idx)
63 {
64 spin_unlock(&__br_write_locks[idx].lock);
65 }
66
67 #endif /* __BRLOCK_USE_ATOMICS */
68
69 #endif /* CONFIG_SMP */
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