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lglock.h
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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 /* can make br locks by using local lock for read side, global lock for write */
29 #define br_lock_init(name) lg_lock_init(name, #name)
30 #define br_read_lock(name) lg_local_lock(name)
31 #define br_read_unlock(name) lg_local_unlock(name)
32 #define br_write_lock(name) lg_global_lock(name)
33 #define br_write_unlock(name) lg_global_unlock(name)
34 
35 #define DEFINE_BRLOCK(name) DEFINE_LGLOCK(name)
36 #define DEFINE_STATIC_BRLOCK(name) DEFINE_STATIC_LGLOCK(name)
37 
38 #ifdef CONFIG_DEBUG_LOCK_ALLOC
39 #define LOCKDEP_INIT_MAP lockdep_init_map
40 #else
41 #define LOCKDEP_INIT_MAP(a, b, c, d)
42 #endif
43 
44 struct lglock {
46 #ifdef CONFIG_DEBUG_LOCK_ALLOC
47  struct lock_class_key lock_key;
48  struct lockdep_map lock_dep_map;
49 #endif
50 };
51 
52 #define DEFINE_LGLOCK(name) \
53  static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
54  = __ARCH_SPIN_LOCK_UNLOCKED; \
55  struct lglock name = { .lock = &name ## _lock }
56 
57 #define DEFINE_STATIC_LGLOCK(name) \
58  static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
59  = __ARCH_SPIN_LOCK_UNLOCKED; \
60  static struct lglock name = { .lock = &name ## _lock }
61 
62 void lg_lock_init(struct lglock *lg, char *name);
63 void lg_local_lock(struct lglock *lg);
64 void lg_local_unlock(struct lglock *lg);
65 void lg_local_lock_cpu(struct lglock *lg, int cpu);
66 void lg_local_unlock_cpu(struct lglock *lg, int cpu);
67 void lg_global_lock(struct lglock *lg);
68 void lg_global_unlock(struct lglock *lg);
69 
70 #endif