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1 /*
2 * Specialised local-global spinlock. Can only be declared as global variables
3 * to avoid overhead and keep things simple (and we don't want to start using
4 * these inside dynamically allocated structures).
5 *
6 * "local/global locks" (lglocks) can be used to:
7 *
8 * - Provide fast exclusive access to per-CPU data, with exclusive access to
9 * another CPU's data allowed but possibly subject to contention, and to
10 * provide very slow exclusive access to all per-CPU data.
11 * - Or to provide very fast and scalable read serialisation, and to provide
12 * very slow exclusive serialisation of data (not necessarily per-CPU data).
13 *
14 * Brlocks are also implemented as a short-hand notation for the latter use
15 * case.
16 *
17 * Copyright 2009, 2010, Nick Piggin, Novell Inc.
18 */
19 #ifndef __LINUX_LGLOCK_H
20 #define __LINUX_LGLOCK_H
21
22 #include <linux/spinlock.h>
23 #include <linux/lockdep.h>
24 #include <linux/percpu.h>
25 #include <linux/cpu.h>
26 #include <linux/notifier.h>
27
28 #ifdef CONFIG_SMP
29
30 #ifdef CONFIG_DEBUG_LOCK_ALLOC
31 #define LOCKDEP_INIT_MAP lockdep_init_map
32 #else
33 #define LOCKDEP_INIT_MAP(a, b, c, d)
34 #endif
35
36 struct lglock {
37 arch_spinlock_t __percpu *lock;
38 #ifdef CONFIG_DEBUG_LOCK_ALLOC
39 struct lock_class_key lock_key;
40 struct lockdep_map lock_dep_map;
41 #endif
42 };
43
44 #define DEFINE_LGLOCK(name) \
45 static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
46 = __ARCH_SPIN_LOCK_UNLOCKED; \
47 struct lglock name = { .lock = &name ## _lock }
48
49 #define DEFINE_STATIC_LGLOCK(name) \
50 static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
51 = __ARCH_SPIN_LOCK_UNLOCKED; \
52 static struct lglock name = { .lock = &name ## _lock }
53
54 void lg_lock_init(struct lglock *lg, char *name);
55 void lg_local_lock(struct lglock *lg);
56 void lg_local_unlock(struct lglock *lg);
57 void lg_local_lock_cpu(struct lglock *lg, int cpu);
58 void lg_local_unlock_cpu(struct lglock *lg, int cpu);
59 void lg_global_lock(struct lglock *lg);
60 void lg_global_unlock(struct lglock *lg);
61
62 #else
63 /* When !CONFIG_SMP, map lglock to spinlock */
64 #define lglock spinlock
65 #define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name)
66 #define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name)
67 #define lg_lock_init(lg, name) spin_lock_init(lg)
68 #define lg_local_lock spin_lock
69 #define lg_local_unlock spin_unlock
70 #define lg_local_lock_cpu(lg, cpu) spin_lock(lg)
71 #define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg)
72 #define lg_global_lock spin_lock
73 #define lg_global_unlock spin_unlock
74 #endif
75
76 #endif