[PATCH] lockdep: prove rwsem locking correctness
[linux-2.6.git] / include / linux / rwsem-spinlock.h
1 /* rwsem-spinlock.h: fallback C implementation
2  *
3  * Copyright (c) 2001   David Howells (dhowells@redhat.com).
4  * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
5  * - Derived also from comments by Linus
6  */
7
8 #ifndef _LINUX_RWSEM_SPINLOCK_H
9 #define _LINUX_RWSEM_SPINLOCK_H
10
11 #ifndef _LINUX_RWSEM_H
12 #error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
13 #endif
14
15 #include <linux/spinlock.h>
16 #include <linux/list.h>
17
18 #ifdef __KERNEL__
19
20 #include <linux/types.h>
21
22 struct rwsem_waiter;
23
24 /*
25  * the rw-semaphore definition
26  * - if activity is 0 then there are no active readers or writers
27  * - if activity is +ve then that is the number of active readers
28  * - if activity is -1 then there is one active writer
29  * - if wait_list is not empty, then there are processes waiting for the semaphore
30  */
31 struct rw_semaphore {
32         __s32                   activity;
33         spinlock_t              wait_lock;
34         struct list_head        wait_list;
35 #ifdef CONFIG_DEBUG_LOCK_ALLOC
36         struct lockdep_map dep_map;
37 #endif
38 };
39
40 #ifdef CONFIG_DEBUG_LOCK_ALLOC
41 # define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
42 #else
43 # define __RWSEM_DEP_MAP_INIT(lockname)
44 #endif
45
46 #define __RWSEM_INITIALIZER(name) \
47 { 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
48
49 #define DECLARE_RWSEM(name) \
50         struct rw_semaphore name = __RWSEM_INITIALIZER(name)
51
52 extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
53                          struct lock_class_key *key);
54
55 #define init_rwsem(sem)                                         \
56 do {                                                            \
57         static struct lock_class_key __key;                     \
58                                                                 \
59         __init_rwsem((sem), #sem, &__key);                      \
60 } while (0)
61
62 extern void FASTCALL(__down_read(struct rw_semaphore *sem));
63 extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
64 extern void FASTCALL(__down_write(struct rw_semaphore *sem));
65 extern void FASTCALL(__down_write_nested(struct rw_semaphore *sem, int subclass));
66 extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
67 extern void FASTCALL(__up_read(struct rw_semaphore *sem));
68 extern void FASTCALL(__up_write(struct rw_semaphore *sem));
69 extern void FASTCALL(__downgrade_write(struct rw_semaphore *sem));
70
71 static inline int rwsem_is_locked(struct rw_semaphore *sem)
72 {
73         return (sem->activity != 0);
74 }
75
76 #endif /* __KERNEL__ */
77 #endif /* _LINUX_RWSEM_SPINLOCK_H */