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
|
/*
* SMP- and interrupt-safe semaphores helper functions.
*
* Copyright (C) 1996 Linus Torvalds
* Copyright (C) 1999 Andrea Arcangeli
* Copyright (C) 1999 Ralf Baechle
* Copyright (C) 1999 Silicon Graphics, Inc.
* Copyright (C) 2000 MIPS Technologies, Inc.
*/
#ifndef _ASM_SEMAPHORE_HELPER_H
#define _ASM_SEMAPHORE_HELPER_H
#include <linux/config.h>
#define sem_read(a) ((a)->counter)
#define sem_inc(a) (((a)->counter)++)
#define sem_dec(a) (((a)->counter)--)
/*
* These two _must_ execute atomically wrt each other.
*/
static inline void wake_one_more(struct semaphore * sem)
{
atomic_inc(&sem->waking);
}
#ifdef CONFIG_CPU_HAS_LLSC
static inline int waking_non_zero(struct semaphore *sem)
{
int ret, tmp;
__asm__ __volatile__(
"1:\tll\t%1, %2\t\t\t# waking_non_zero\n\t"
"blez\t%1, 2f\n\t"
"subu\t%0, %1, 1\n\t"
"sc\t%0, %2\n\t"
"beqz\t%0, 1b\n"
"2:"
: "=r" (ret), "=r" (tmp), "+m" (sem->waking)
: "0"(0));
return ret;
}
#else /* !CONFIG_CPU_HAS_LLSC */
/*
* It doesn't make sense, IMHO, to endlessly turn interrupts off and on again.
* Do it once and that's it. ll/sc *has* it's advantages. HK
*/
static inline int waking_non_zero(struct semaphore *sem)
{
unsigned long flags;
int ret = 0;
local_irq_save(flags);
if (sem_read(&sem->waking) > 0) {
sem_dec(&sem->waking);
ret = 1;
}
local_irq_restore(flags);
return ret;
}
#endif /* !CONFIG_CPU_HAS_LLSC */
#ifdef CONFIG_CPU_HAS_LLDSCD
/*
* waking_non_zero_interruptible:
* 1 got the lock
* 0 go to sleep
* -EINTR interrupted
*
* We must undo the sem->count down_interruptible decrement
* simultaneously and atomically with the sem->waking adjustment,
* otherwise we can race with wake_one_more.
*
* This is accomplished by doing a 64-bit lld/scd on the 2 32-bit words.
*
* This is crazy. Normally it's strictly forbidden to use 64-bit operations
* in the 32-bit MIPS kernel. In this case it's however ok because if an
* interrupt has destroyed the upper half of registers sc will fail.
* Note also that this will not work for MIPS32 CPUs!
*
* Pseudocode:
*
* If(sem->waking > 0) {
* Decrement(sem->waking)
* Return(SUCCESS)
* } else If(signal_pending(tsk)) {
* Increment(sem->count)
* Return(-EINTR)
* } else {
* Return(SLEEP)
* }
*/
static inline int
waking_non_zero_interruptible(struct semaphore *sem, struct task_struct *tsk)
{
long ret, tmp;
__asm__ __volatile__(
".set\tpush\n\t"
".set\tmips3\n\t"
".set\tnoat\n"
"0:\tlld\t%1, %2\n\t"
"li\t%0, 0\n\t"
"sll\t$1, %1, 0\n\t"
"blez\t$1, 1f\n\t"
"daddiu\t%1, %1, -1\n\t"
"li\t%0, 1\n\t"
"b\t2f\n"
"1:\tbeqz\t%3, 2f\n\t"
"li\t%0, %4\n\t"
"dli\t$1, 0x0000000100000000\n\t"
"daddu\t%1, %1, $1\n"
"2:\tscd\t%1, %2\n\t"
"beqz\t%1, 0b\n\t"
".set\tpop"
: "=&r" (ret), "=&r" (tmp), "=m" (*sem)
: "r" (signal_pending(tsk)), "i" (-EINTR));
return ret;
}
/*
* waking_non_zero_trylock is unused. we do everything in
* down_trylock and let non-ll/sc hosts bounce around.
*/
static inline int waking_non_zero_trylock(struct semaphore *sem)
{
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
return 0;
}
#else /* !CONFIG_CPU_HAS_LLDSCD */
static inline int waking_non_zero_interruptible(struct semaphore *sem,
struct task_struct *tsk)
{
int ret = 0;
unsigned long flags;
local_irq_save(flags);
if (sem_read(&sem->waking) > 0) {
sem_dec(&sem->waking);
ret = 1;
} else if (signal_pending(tsk)) {
sem_inc(&sem->count);
ret = -EINTR;
}
local_irq_restore(flags);
return ret;
}
static inline int waking_non_zero_trylock(struct semaphore *sem)
{
int ret = 1;
unsigned long flags;
local_irq_save(flags);
if (sem_read(&sem->waking) <= 0)
sem_inc(&sem->count);
else {
sem_dec(&sem->waking);
ret = 0;
}
local_irq_restore(flags);
return ret;
}
#endif /* !CONFIG_CPU_HAS_LLDSCD */
#endif /* _ASM_SEMAPHORE_HELPER_H */
|
