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
|
/*
* R/W semaphores for ia64
*
* Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com>
* Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com>
* Copyright (C) 2005 Christoph Lameter <cl@linux.com>
*
* Based on asm-i386/rwsem.h and other architecture implementation.
*
* The MSW of the count is the negated number of active writers and
* waiting lockers, and the LSW is the total number of active locks.
*
* The lock count is initialized to 0 (no active and no waiting lockers).
*
* When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for
* the case of an uncontended lock. Readers increment by 1 and see a positive
* value when uncontended, negative if there are writers (and maybe) readers
* waiting (in which case it goes to sleep).
*/
#ifndef _ASM_IA64_RWSEM_H
#define _ASM_IA64_RWSEM_H
#ifndef _LINUX_RWSEM_H
#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
#endif
#include <asm/intrinsics.h>
#define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000)
#define RWSEM_ACTIVE_BIAS (1L)
#define RWSEM_ACTIVE_MASK (0xffffffffL)
#define RWSEM_WAITING_BIAS (-0x100000000L)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
/*
* lock for reading
*/
static inline void
__down_read (struct rw_semaphore *sem)
{
long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1);
if (result < 0)
rwsem_down_read_failed(sem);
}
/*
* lock for writing
*/
static inline long
___down_write (struct rw_semaphore *sem)
{
long old, new;
do {
old = atomic_long_read(&sem->count);
new = old + RWSEM_ACTIVE_WRITE_BIAS;
} while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old);
return old;
}
static inline void
__down_write (struct rw_semaphore *sem)
{
if (___down_write(sem))
rwsem_down_write_failed(sem);
}
static inline int
__down_write_killable (struct rw_semaphore *sem)
{
if (___down_write(sem))
if (IS_ERR(rwsem_down_write_failed_killable(sem)))
return -EINTR;
return 0;
}
/*
* unlock after reading
*/
static inline void
__up_read (struct rw_semaphore *sem)
{
long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1);
if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
rwsem_wake(sem);
}
/*
* unlock after writing
*/
static inline void
__up_write (struct rw_semaphore *sem)
{
long old, new;
do {
old = atomic_long_read(&sem->count);
new = old - RWSEM_ACTIVE_WRITE_BIAS;
} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
rwsem_wake(sem);
}
/*
* trylock for reading -- returns 1 if successful, 0 if contention
*/
static inline int
__down_read_trylock (struct rw_semaphore *sem)
{
long tmp;
while ((tmp = atomic_long_read(&sem->count)) >= 0) {
if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) {
return 1;
}
}
return 0;
}
/*
* trylock for writing -- returns 1 if successful, 0 if contention
*/
static inline int
__down_write_trylock (struct rw_semaphore *sem)
{
long tmp = atomic_long_cmpxchg_acquire(&sem->count,
RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS);
return tmp == RWSEM_UNLOCKED_VALUE;
}
/*
* downgrade write lock to read lock
*/
static inline void
__downgrade_write (struct rw_semaphore *sem)
{
long old, new;
do {
old = atomic_long_read(&sem->count);
new = old - RWSEM_WAITING_BIAS;
} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
if (old < 0)
rwsem_downgrade_wake(sem);
}
/*
* Implement atomic add functionality. These used to be "inline" functions, but GCC v3.1
* doesn't quite optimize this stuff right and ends up with bad calls to fetchandadd.
*/
#define rwsem_atomic_add(delta, sem) atomic64_add(delta, (atomic64_t *)(&(sem)->count))
#define rwsem_atomic_update(delta, sem) atomic64_add_return(delta, (atomic64_t *)(&(sem)->count))
#endif /* _ASM_IA64_RWSEM_H */
|
