1#ifndef _ALPHA_RWSEM_H
2#define _ALPHA_RWSEM_H
3
4/*
5 * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001.
6 * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
7 */
8
9#ifndef _LINUX_RWSEM_H
10#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
11#endif
12
13#ifdef __KERNEL__
14
15#include <linux/compiler.h>
16#include <linux/list.h>
17#include <linux/spinlock.h>
18
19struct rwsem_waiter;
20
21extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
22extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
23extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
24extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
25
26/*
27 * the semaphore definition
28 */
29struct rw_semaphore {
30	long			count;
31#define RWSEM_UNLOCKED_VALUE		0x0000000000000000L
32#define RWSEM_ACTIVE_BIAS		0x0000000000000001L
33#define RWSEM_ACTIVE_MASK		0x00000000ffffffffL
34#define RWSEM_WAITING_BIAS		(-0x0000000100000000L)
35#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
36#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
37	spinlock_t		wait_lock;
38	struct list_head	wait_list;
39};
40
41#define __RWSEM_INITIALIZER(name) \
42	{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
43	LIST_HEAD_INIT((name).wait_list) }
44
45#define DECLARE_RWSEM(name) \
46	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
47
48static inline void init_rwsem(struct rw_semaphore *sem)
49{
50	sem->count = RWSEM_UNLOCKED_VALUE;
51	spin_lock_init(&sem->wait_lock);
52	INIT_LIST_HEAD(&sem->wait_list);
53}
54
55static inline void __down_read(struct rw_semaphore *sem)
56{
57	long oldcount;
58#ifndef	CONFIG_SMP
59	oldcount = sem->count;
60	sem->count += RWSEM_ACTIVE_READ_BIAS;
61#else
62	long temp;
63	__asm__ __volatile__(
64	"1:	ldq_l	%0,%1\n"
65	"	addq	%0,%3,%2\n"
66	"	stq_c	%2,%1\n"
67	"	beq	%2,2f\n"
68	"	mb\n"
69	".subsection 2\n"
70	"2:	br	1b\n"
71	".previous"
72	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
73	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
74#endif
75	if (unlikely(oldcount < 0))
76		rwsem_down_read_failed(sem);
77}
78
79/*
80 * trylock for reading -- returns 1 if successful, 0 if contention
81 */
82static inline int __down_read_trylock(struct rw_semaphore *sem)
83{
84	long old, new, res;
85
86	res = sem->count;
87	do {
88		new = res + RWSEM_ACTIVE_READ_BIAS;
89		if (new <= 0)
90			break;
91		old = res;
92		res = cmpxchg(&sem->count, old, new);
93	} while (res != old);
94	return res >= 0 ? 1 : 0;
95}
96
97static inline void __down_write(struct rw_semaphore *sem)
98{
99	long oldcount;
100#ifndef	CONFIG_SMP
101	oldcount = sem->count;
102	sem->count += RWSEM_ACTIVE_WRITE_BIAS;
103#else
104	long temp;
105	__asm__ __volatile__(
106	"1:	ldq_l	%0,%1\n"
107	"	addq	%0,%3,%2\n"
108	"	stq_c	%2,%1\n"
109	"	beq	%2,2f\n"
110	"	mb\n"
111	".subsection 2\n"
112	"2:	br	1b\n"
113	".previous"
114	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
115	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
116#endif
117	if (unlikely(oldcount))
118		rwsem_down_write_failed(sem);
119}
120
121/*
122 * trylock for writing -- returns 1 if successful, 0 if contention
123 */
124static inline int __down_write_trylock(struct rw_semaphore *sem)
125{
126	long ret = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
127			   RWSEM_ACTIVE_WRITE_BIAS);
128	if (ret == RWSEM_UNLOCKED_VALUE)
129		return 1;
130	return 0;
131}
132
133static inline void __up_read(struct rw_semaphore *sem)
134{
135	long oldcount;
136#ifndef	CONFIG_SMP
137	oldcount = sem->count;
138	sem->count -= RWSEM_ACTIVE_READ_BIAS;
139#else
140	long temp;
141	__asm__ __volatile__(
142	"	mb\n"
143	"1:	ldq_l	%0,%1\n"
144	"	subq	%0,%3,%2\n"
145	"	stq_c	%2,%1\n"
146	"	beq	%2,2f\n"
147	".subsection 2\n"
148	"2:	br	1b\n"
149	".previous"
150	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
151	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
152#endif
153	if (unlikely(oldcount < 0))
154		if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
155			rwsem_wake(sem);
156}
157
158static inline void __up_write(struct rw_semaphore *sem)
159{
160	long count;
161#ifndef	CONFIG_SMP
162	sem->count -= RWSEM_ACTIVE_WRITE_BIAS;
163	count = sem->count;
164#else
165	long temp;
166	__asm__ __volatile__(
167	"	mb\n"
168	"1:	ldq_l	%0,%1\n"
169	"	subq	%0,%3,%2\n"
170	"	stq_c	%2,%1\n"
171	"	beq	%2,2f\n"
172	"	subq	%0,%3,%0\n"
173	".subsection 2\n"
174	"2:	br	1b\n"
175	".previous"
176	:"=&r" (count), "=m" (sem->count), "=&r" (temp)
177	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
178#endif
179	if (unlikely(count))
180		if ((int)count == 0)
181			rwsem_wake(sem);
182}
183
184/*
185 * downgrade write lock to read lock
186 */
187static inline void __downgrade_write(struct rw_semaphore *sem)
188{
189	long oldcount;
190#ifndef	CONFIG_SMP
191	oldcount = sem->count;
192	sem->count -= RWSEM_WAITING_BIAS;
193#else
194	long temp;
195	__asm__ __volatile__(
196	"1:	ldq_l	%0,%1\n"
197	"	addq	%0,%3,%2\n"
198	"	stq_c	%2,%1\n"
199	"	beq	%2,2f\n"
200	"	mb\n"
201	".subsection 2\n"
202	"2:	br	1b\n"
203	".previous"
204	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
205	:"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
206#endif
207	if (unlikely(oldcount < 0))
208		rwsem_downgrade_wake(sem);
209}
210
211static inline void rwsem_atomic_add(long val, struct rw_semaphore *sem)
212{
213#ifndef	CONFIG_SMP
214	sem->count += val;
215#else
216	long temp;
217	__asm__ __volatile__(
218	"1:	ldq_l	%0,%1\n"
219	"	addq	%0,%2,%0\n"
220	"	stq_c	%0,%1\n"
221	"	beq	%0,2f\n"
222	".subsection 2\n"
223	"2:	br	1b\n"
224	".previous"
225	:"=&r" (temp), "=m" (sem->count)
226	:"Ir" (val), "m" (sem->count));
227#endif
228}
229
230static inline long rwsem_atomic_update(long val, struct rw_semaphore *sem)
231{
232#ifndef	CONFIG_SMP
233	sem->count += val;
234	return sem->count;
235#else
236	long ret, temp;
237	__asm__ __volatile__(
238	"1:	ldq_l	%0,%1\n"
239	"	addq 	%0,%3,%2\n"
240	"	addq	%0,%3,%0\n"
241	"	stq_c	%2,%1\n"
242	"	beq	%2,2f\n"
243	".subsection 2\n"
244	"2:	br	1b\n"
245	".previous"
246	:"=&r" (ret), "=m" (sem->count), "=&r" (temp)
247	:"Ir" (val), "m" (sem->count));
248
249	return ret;
250#endif
251}
252
253static inline int rwsem_is_locked(struct rw_semaphore *sem)
254{
255	return (sem->count != 0);
256}
257
258#endif /* __KERNEL__ */
259#endif /* _ALPHA_RWSEM_H */
260