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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * R/W semaphores for ia64
4 *
5 * Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com>
6 * Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com>
7 * Copyright (C) 2005 Christoph Lameter <cl@linux.com>
8 *
9 * Based on asm-i386/rwsem.h and other architecture implementation.
10 *
11 * The MSW of the count is the negated number of active writers and
12 * waiting lockers, and the LSW is the total number of active locks.
13 *
14 * The lock count is initialized to 0 (no active and no waiting lockers).
15 *
16 * When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for
17 * the case of an uncontended lock. Readers increment by 1 and see a positive
18 * value when uncontended, negative if there are writers (and maybe) readers
19 * waiting (in which case it goes to sleep).
20 */
21
22#ifndef _ASM_IA64_RWSEM_H
23#define _ASM_IA64_RWSEM_H
24
25#ifndef _LINUX_RWSEM_H
26#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
27#endif
28
29#include <asm/intrinsics.h>
30
31#define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000)
32#define RWSEM_ACTIVE_BIAS (1L)
33#define RWSEM_ACTIVE_MASK (0xffffffffL)
34#define RWSEM_WAITING_BIAS (-0x100000000L)
35#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
36#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
37
38/*
39 * lock for reading
40 */
41static inline int
42___down_read (struct rw_semaphore *sem)
43{
44 long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1);
45
46 return (result < 0);
47}
48
49static inline void
50__down_read (struct rw_semaphore *sem)
51{
52 if (___down_read(sem))
53 rwsem_down_read_failed(sem);
54}
55
56static inline int
57__down_read_killable (struct rw_semaphore *sem)
58{
59 if (___down_read(sem))
60 if (IS_ERR(rwsem_down_read_failed_killable(sem)))
61 return -EINTR;
62
63 return 0;
64}
65
66/*
67 * lock for writing
68 */
69static inline long
70___down_write (struct rw_semaphore *sem)
71{
72 long old, new;
73
74 do {
75 old = atomic_long_read(&sem->count);
76 new = old + RWSEM_ACTIVE_WRITE_BIAS;
77 } while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old);
78
79 return old;
80}
81
82static inline void
83__down_write (struct rw_semaphore *sem)
84{
85 if (___down_write(sem))
86 rwsem_down_write_failed(sem);
87}
88
89static inline int
90__down_write_killable (struct rw_semaphore *sem)
91{
92 if (___down_write(sem)) {
93 if (IS_ERR(rwsem_down_write_failed_killable(sem)))
94 return -EINTR;
95 }
96
97 return 0;
98}
99
100/*
101 * unlock after reading
102 */
103static inline void
104__up_read (struct rw_semaphore *sem)
105{
106 long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1);
107
108 if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
109 rwsem_wake(sem);
110}
111
112/*
113 * unlock after writing
114 */
115static inline void
116__up_write (struct rw_semaphore *sem)
117{
118 long old, new;
119
120 do {
121 old = atomic_long_read(&sem->count);
122 new = old - RWSEM_ACTIVE_WRITE_BIAS;
123 } while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
124
125 if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
126 rwsem_wake(sem);
127}
128
129/*
130 * trylock for reading -- returns 1 if successful, 0 if contention
131 */
132static inline int
133__down_read_trylock (struct rw_semaphore *sem)
134{
135 long tmp;
136 while ((tmp = atomic_long_read(&sem->count)) >= 0) {
137 if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) {
138 return 1;
139 }
140 }
141 return 0;
142}
143
144/*
145 * trylock for writing -- returns 1 if successful, 0 if contention
146 */
147static inline int
148__down_write_trylock (struct rw_semaphore *sem)
149{
150 long tmp = atomic_long_cmpxchg_acquire(&sem->count,
151 RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS);
152 return tmp == RWSEM_UNLOCKED_VALUE;
153}
154
155/*
156 * downgrade write lock to read lock
157 */
158static inline void
159__downgrade_write (struct rw_semaphore *sem)
160{
161 long old, new;
162
163 do {
164 old = atomic_long_read(&sem->count);
165 new = old - RWSEM_WAITING_BIAS;
166 } while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
167
168 if (old < 0)
169 rwsem_downgrade_wake(sem);
170}
171
172#endif /* _ASM_IA64_RWSEM_H */