1/* $Id: semaphore.h,v 1.1.1.1 2007/08/03 18:53:22 Exp $ */
2
3/* On the i386 these are coded in asm, perhaps we should as well. Later.. */
4
5#ifndef _CRIS_SEMAPHORE_H
6#define _CRIS_SEMAPHORE_H
7
8#define RW_LOCK_BIAS             0x01000000
9
10#include <linux/wait.h>
11#include <linux/spinlock.h>
12#include <linux/rwsem.h>
13
14#include <asm/system.h>
15#include <asm/atomic.h>
16
17/*
18 * CRIS semaphores, implemented in C-only so far.
19 */
20
21struct semaphore {
22	atomic_t count;
23	atomic_t waking;
24	wait_queue_head_t wait;
25};
26
27#define __SEMAPHORE_INITIALIZER(name, n)				\
28{									\
29	.count		= ATOMIC_INIT(n),				\
30	.waking		= ATOMIC_INIT(0),				\
31	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)    \
32}
33
34#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
35        struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
36
37#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
38#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
39
40static inline void sema_init(struct semaphore *sem, int val)
41{
42	*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
43}
44
45static inline void init_MUTEX (struct semaphore *sem)
46{
47        sema_init(sem, 1);
48}
49
50static inline void init_MUTEX_LOCKED (struct semaphore *sem)
51{
52        sema_init(sem, 0);
53}
54
55extern void __down(struct semaphore * sem);
56extern int __down_interruptible(struct semaphore * sem);
57extern int __down_trylock(struct semaphore * sem);
58extern void __up(struct semaphore * sem);
59
60/* notice - we probably can do cli/sti here instead of saving */
61
62static inline void down(struct semaphore * sem)
63{
64	unsigned long flags;
65	int failed;
66
67	might_sleep();
68
69	/* atomically decrement the semaphores count, and if its negative, we wait */
70	cris_atomic_save(sem, flags);
71	failed = --(sem->count.counter) < 0;
72	cris_atomic_restore(sem, flags);
73	if(failed) {
74		__down(sem);
75	}
76}
77
78/*
79 * This version waits in interruptible state so that the waiting
80 * process can be killed.  The down_interruptible routine
81 * returns negative for signalled and zero for semaphore acquired.
82 */
83
84static inline int down_interruptible(struct semaphore * sem)
85{
86	unsigned long flags;
87	int failed;
88
89	might_sleep();
90
91	/* atomically decrement the semaphores count, and if its negative, we wait */
92	cris_atomic_save(sem, flags);
93	failed = --(sem->count.counter) < 0;
94	cris_atomic_restore(sem, flags);
95	if(failed)
96		failed = __down_interruptible(sem);
97	return(failed);
98}
99
100static inline int down_trylock(struct semaphore * sem)
101{
102	unsigned long flags;
103	int failed;
104
105	cris_atomic_save(sem, flags);
106	failed = --(sem->count.counter) < 0;
107	cris_atomic_restore(sem, flags);
108	if(failed)
109		failed = __down_trylock(sem);
110	return(failed);
111
112}
113
114/*
115 * Note! This is subtle. We jump to wake people up only if
116 * the semaphore was negative (== somebody was waiting on it).
117 * The default case (no contention) will result in NO
118 * jumps for both down() and up().
119 */
120static inline void up(struct semaphore * sem)
121{
122	unsigned long flags;
123	int wakeup;
124
125	/* atomically increment the semaphores count, and if it was negative, we wake people */
126	cris_atomic_save(sem, flags);
127	wakeup = ++(sem->count.counter) <= 0;
128	cris_atomic_restore(sem, flags);
129	if(wakeup) {
130		__up(sem);
131	}
132}
133
134#endif
135