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 compat_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 __COMPAT_RWSEM_INITIALIZER(name) \
47 { 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
48
49 #define COMPAT_DECLARE_RWSEM(name) \
50 struct compat_rw_semaphore name = __COMPAT_RWSEM_INITIALIZER(name)
51
52 extern void __compat_init_rwsem(struct compat_rw_semaphore *sem, const char *name,
53 struct lock_class_key *key);
54
55 #define compat_init_rwsem(sem) \
56 do { \
57 static struct lock_class_key __key; \
58 \
59 __compat_init_rwsem((sem), #sem, &__key); \
60 } while (0)
61
62 extern void __down_read(struct compat_rw_semaphore *sem);
63 extern int __down_read_trylock(struct compat_rw_semaphore *sem);
64 extern void __down_write(struct compat_rw_semaphore *sem);
65 extern void __down_write_nested(struct compat_rw_semaphore *sem, int subclass);
66 extern int __down_write_trylock(struct compat_rw_semaphore *sem);
67 extern void __up_read(struct compat_rw_semaphore *sem);
68 extern void __up_write(struct compat_rw_semaphore *sem);
69 extern void __downgrade_write(struct compat_rw_semaphore *sem);
70
71 static inline int compat_rwsem_is_locked(struct compat_rw_semaphore *sem)
72 {
73 return (sem->activity != 0);
74 }
75
76 #endif /* __KERNEL__ */
77 #endif /* _LINUX_RWSEM_SPINLOCK_H */
78
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