1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ALPHA_RWSEM_H
3 #define _ALPHA_RWSEM_H
4
5 /*
6 * Written by Ivan Kokshaysky <ink@jurassic.park.msu.ru>, 2001.
7 * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
8 */
9
10 #ifndef _LINUX_RWSEM_H
11 #error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
12 #endif
13
14 #ifdef __KERNEL__
15
16 #include <linux/compiler.h>
17
18 #define RWSEM_UNLOCKED_VALUE 0x0000000000000000L
19 #define RWSEM_ACTIVE_BIAS 0x0000000000000001L
20 #define RWSEM_ACTIVE_MASK 0x00000000ffffffffL
21 #define RWSEM_WAITING_BIAS (-0x0000000100000000L)
22 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
23 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
24
___down_read(struct rw_semaphore * sem)25 static inline int ___down_read(struct rw_semaphore *sem)
26 {
27 long oldcount;
28 #ifndef CONFIG_SMP
29 oldcount = sem->count.counter;
30 sem->count.counter += RWSEM_ACTIVE_READ_BIAS;
31 #else
32 long temp;
33 __asm__ __volatile__(
34 "1: ldq_l %0,%1\n"
35 " addq %0,%3,%2\n"
36 " stq_c %2,%1\n"
37 " beq %2,2f\n"
38 " mb\n"
39 ".subsection 2\n"
40 "2: br 1b\n"
41 ".previous"
42 :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
43 :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
44 #endif
45 return (oldcount < 0);
46 }
47
__down_read(struct rw_semaphore * sem)48 static inline void __down_read(struct rw_semaphore *sem)
49 {
50 if (unlikely(___down_read(sem)))
51 rwsem_down_read_failed(sem);
52 }
53
__down_read_killable(struct rw_semaphore * sem)54 static inline int __down_read_killable(struct rw_semaphore *sem)
55 {
56 if (unlikely(___down_read(sem)))
57 if (IS_ERR(rwsem_down_read_failed_killable(sem)))
58 return -EINTR;
59
60 return 0;
61 }
62
63 /*
64 * trylock for reading -- returns 1 if successful, 0 if contention
65 */
__down_read_trylock(struct rw_semaphore * sem)66 static inline int __down_read_trylock(struct rw_semaphore *sem)
67 {
68 long old, new, res;
69
70 res = atomic_long_read(&sem->count);
71 do {
72 new = res + RWSEM_ACTIVE_READ_BIAS;
73 if (new <= 0)
74 break;
75 old = res;
76 res = atomic_long_cmpxchg(&sem->count, old, new);
77 } while (res != old);
78 return res >= 0 ? 1 : 0;
79 }
80
___down_write(struct rw_semaphore * sem)81 static inline long ___down_write(struct rw_semaphore *sem)
82 {
83 long oldcount;
84 #ifndef CONFIG_SMP
85 oldcount = sem->count.counter;
86 sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
87 #else
88 long temp;
89 __asm__ __volatile__(
90 "1: ldq_l %0,%1\n"
91 " addq %0,%3,%2\n"
92 " stq_c %2,%1\n"
93 " beq %2,2f\n"
94 " mb\n"
95 ".subsection 2\n"
96 "2: br 1b\n"
97 ".previous"
98 :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
99 :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
100 #endif
101 return oldcount;
102 }
103
__down_write(struct rw_semaphore * sem)104 static inline void __down_write(struct rw_semaphore *sem)
105 {
106 if (unlikely(___down_write(sem)))
107 rwsem_down_write_failed(sem);
108 }
109
__down_write_killable(struct rw_semaphore * sem)110 static inline int __down_write_killable(struct rw_semaphore *sem)
111 {
112 if (unlikely(___down_write(sem))) {
113 if (IS_ERR(rwsem_down_write_failed_killable(sem)))
114 return -EINTR;
115 }
116
117 return 0;
118 }
119
120 /*
121 * trylock for writing -- returns 1 if successful, 0 if contention
122 */
__down_write_trylock(struct rw_semaphore * sem)123 static inline int __down_write_trylock(struct rw_semaphore *sem)
124 {
125 long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
126 RWSEM_ACTIVE_WRITE_BIAS);
127 if (ret == RWSEM_UNLOCKED_VALUE)
128 return 1;
129 return 0;
130 }
131
__up_read(struct rw_semaphore * sem)132 static inline void __up_read(struct rw_semaphore *sem)
133 {
134 long oldcount;
135 #ifndef CONFIG_SMP
136 oldcount = sem->count.counter;
137 sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
138 #else
139 long temp;
140 __asm__ __volatile__(
141 " mb\n"
142 "1: ldq_l %0,%1\n"
143 " subq %0,%3,%2\n"
144 " stq_c %2,%1\n"
145 " beq %2,2f\n"
146 ".subsection 2\n"
147 "2: br 1b\n"
148 ".previous"
149 :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
150 :"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
151 #endif
152 if (unlikely(oldcount < 0))
153 if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
154 rwsem_wake(sem);
155 }
156
__up_write(struct rw_semaphore * sem)157 static inline void __up_write(struct rw_semaphore *sem)
158 {
159 long count;
160 #ifndef CONFIG_SMP
161 sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
162 count = sem->count.counter;
163 #else
164 long temp;
165 __asm__ __volatile__(
166 " mb\n"
167 "1: ldq_l %0,%1\n"
168 " subq %0,%3,%2\n"
169 " stq_c %2,%1\n"
170 " beq %2,2f\n"
171 " subq %0,%3,%0\n"
172 ".subsection 2\n"
173 "2: br 1b\n"
174 ".previous"
175 :"=&r" (count), "=m" (sem->count), "=&r" (temp)
176 :"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
177 #endif
178 if (unlikely(count))
179 if ((int)count == 0)
180 rwsem_wake(sem);
181 }
182
183 /*
184 * downgrade write lock to read lock
185 */
__downgrade_write(struct rw_semaphore * sem)186 static inline void __downgrade_write(struct rw_semaphore *sem)
187 {
188 long oldcount;
189 #ifndef CONFIG_SMP
190 oldcount = sem->count.counter;
191 sem->count.counter -= RWSEM_WAITING_BIAS;
192 #else
193 long temp;
194 __asm__ __volatile__(
195 "1: ldq_l %0,%1\n"
196 " addq %0,%3,%2\n"
197 " stq_c %2,%1\n"
198 " beq %2,2f\n"
199 " mb\n"
200 ".subsection 2\n"
201 "2: br 1b\n"
202 ".previous"
203 :"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
204 :"Ir" (-RWSEM_WAITING_BIAS), "m" (sem->count) : "memory");
205 #endif
206 if (unlikely(oldcount < 0))
207 rwsem_downgrade_wake(sem);
208 }
209
210 #endif /* __KERNEL__ */
211 #endif /* _ALPHA_RWSEM_H */
212
