summaryrefslogtreecommitdiffstats
path: root/arch/alpha/include/asm/rwsem.h
blob: 9624cb4cbf2fa388cf09ca2f76ba9e087560da67 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
#ifndef _ALPHA_RWSEM_H
#define _ALPHA_RWSEM_H

/*
 * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001.
 * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
 */

#ifndef _LINUX_RWSEM_H
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
#endif

#ifdef __KERNEL__

#include <linux/compiler.h>

#define RWSEM_UNLOCKED_VALUE		0x0000000000000000L
#define RWSEM_ACTIVE_BIAS		0x0000000000000001L
#define RWSEM_ACTIVE_MASK		0x00000000ffffffffL
#define RWSEM_WAITING_BIAS		(-0x0000000100000000L)
#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)

static inline int ___down_read(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count.counter;
	sem->count.counter += RWSEM_ACTIVE_READ_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	mb\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
#endif
	return (oldcount < 0);
}

static inline void __down_read(struct rw_semaphore *sem)
{
	if (unlikely(___down_read(sem)))
		rwsem_down_read_failed(sem);
}

static inline int __down_read_killable(struct rw_semaphore *sem)
{
	if (unlikely(___down_read(sem)))
		if (IS_ERR(rwsem_down_read_failed_killable(sem)))
			return -EINTR;

	return 0;
}

/*
 * trylock for reading -- returns 1 if successful, 0 if contention
 */
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
	long old, new, res;

	res = atomic_long_read(&sem->count);
	do {
		new = res + RWSEM_ACTIVE_READ_BIAS;
		if (new <= 0)
			break;
		old = res;
		res = atomic_long_cmpxchg(&sem->count, old, new);
	} while (res != old);
	return res >= 0 ? 1 : 0;
}

static inline long ___down_write(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count.counter;
	sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	mb\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
#endif
	return oldcount;
}

static inline void __down_write(struct rw_semaphore *sem)
{
	if (unlikely(___down_write(sem)))
		rwsem_down_write_failed(sem);
}

static inline int __down_write_killable(struct rw_semaphore *sem)
{
	if (unlikely(___down_write(sem))) {
		if (IS_ERR(rwsem_down_write_failed_killable(sem)))
			return -EINTR;
	}

	return 0;
}

/*
 * trylock for writing -- returns 1 if successful, 0 if contention
 */
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
	long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
			   RWSEM_ACTIVE_WRITE_BIAS);
	if (ret == RWSEM_UNLOCKED_VALUE)
		return 1;
	return 0;
}

static inline void __up_read(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count.counter;
	sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"	mb\n"
	"1:	ldq_l	%0,%1\n"
	"	subq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
#endif
	if (unlikely(oldcount < 0))
		if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
			rwsem_wake(sem);
}

static inline void __up_write(struct rw_semaphore *sem)
{
	long count;
#ifndef	CONFIG_SMP
	sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
	count = sem->count.counter;
#else
	long temp;
	__asm__ __volatile__(
	"	mb\n"
	"1:	ldq_l	%0,%1\n"
	"	subq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	subq	%0,%3,%0\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (count), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
#endif
	if (unlikely(count))
		if ((int)count == 0)
			rwsem_wake(sem);
}

/*
 * downgrade write lock to read lock
 */
static inline void __downgrade_write(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count.counter;
	sem->count.counter -= RWSEM_WAITING_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	mb\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
#endif
	if (unlikely(oldcount < 0))
		rwsem_downgrade_wake(sem);
}

#endif /* __KERNEL__ */
#endif /* _ALPHA_RWSEM_H */