blob: a93960e232cffabb43de39d78a97dc9d7542f154 (
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
|
#ifndef __ASM_SPINLOCK_H
#define __ASM_SPINLOCK_H
#include <asm/system.h>
#include <asm/processor.h>
#include <asm/spinlock_types.h>
static inline int __raw_spin_is_locked(raw_spinlock_t *x)
{
volatile unsigned int *a = __ldcw_align(x);
return *a == 0;
}
#define __raw_spin_lock(lock) __raw_spin_lock_flags(lock, 0)
#define __raw_spin_unlock_wait(x) \
do { cpu_relax(); } while (__raw_spin_is_locked(x))
static inline void __raw_spin_lock_flags(raw_spinlock_t *x,
unsigned long flags)
{
volatile unsigned int *a;
mb();
a = __ldcw_align(x);
while (__ldcw(a) == 0)
while (*a == 0)
if (flags & PSW_SM_I) {
local_irq_enable();
cpu_relax();
local_irq_disable();
} else
cpu_relax();
mb();
}
static inline void __raw_spin_unlock(raw_spinlock_t *x)
{
volatile unsigned int *a;
mb();
a = __ldcw_align(x);
*a = 1;
mb();
}
static inline int __raw_spin_trylock(raw_spinlock_t *x)
{
volatile unsigned int *a;
int ret;
mb();
a = __ldcw_align(x);
ret = __ldcw(a) != 0;
mb();
return ret;
}
/*
* Read-write spinlocks, allowing multiple readers
* but only one writer.
*/
#define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
/* read_lock, read_unlock are pretty straightforward. Of course it somehow
* sucks we end up saving/restoring flags twice for read_lock_irqsave aso. */
static __inline__ void __raw_read_lock(raw_rwlock_t *rw)
{
__raw_spin_lock(&rw->lock);
rw->counter++;
__raw_spin_unlock(&rw->lock);
}
static __inline__ void __raw_read_unlock(raw_rwlock_t *rw)
{
__raw_spin_lock(&rw->lock);
rw->counter--;
__raw_spin_unlock(&rw->lock);
}
/* write_lock is less trivial. We optimistically grab the lock and check
* if we surprised any readers. If so we release the lock and wait till
* they're all gone before trying again
*
* Also note that we don't use the _irqsave / _irqrestore suffixes here.
* If we're called with interrupts enabled and we've got readers (or other
* writers) in interrupt handlers someone fucked up and we'd dead-lock
* sooner or later anyway. prumpf */
static __inline__ void __raw_write_lock(raw_rwlock_t *rw)
{
retry:
__raw_spin_lock(&rw->lock);
if(rw->counter != 0) {
/* this basically never happens */
__raw_spin_unlock(&rw->lock);
while (rw->counter != 0)
cpu_relax();
goto retry;
}
/* got it. now leave without unlocking */
rw->counter = -1; /* remember we are locked */
}
/* write_unlock is absolutely trivial - we don't have to wait for anything */
static __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
{
rw->counter = 0;
__raw_spin_unlock(&rw->lock);
}
static __inline__ int __raw_write_trylock(raw_rwlock_t *rw)
{
__raw_spin_lock(&rw->lock);
if (rw->counter != 0) {
/* this basically never happens */
__raw_spin_unlock(&rw->lock);
return 0;
}
/* got it. now leave without unlocking */
rw->counter = -1; /* remember we are locked */
return 1;
}
/*
* read_can_lock - would read_trylock() succeed?
* @lock: the rwlock in question.
*/
static __inline__ int __raw_read_can_lock(raw_rwlock_t *rw)
{
return rw->counter >= 0;
}
/*
* write_can_lock - would write_trylock() succeed?
* @lock: the rwlock in question.
*/
static __inline__ int __raw_write_can_lock(raw_rwlock_t *rw)
{
return !rw->counter;
}
#endif /* __ASM_SPINLOCK_H */
|
