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
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
|
/* semaphore.c: Sparc64 semaphore implementation.
*
* This is basically the PPC semaphore scheme ported to use
* the sparc64 atomic instructions, so see the PPC code for
* credits.
*/
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/init.h>
/*
* Atomically update sem->count.
* This does the equivalent of the following:
*
* old_count = sem->count;
* tmp = MAX(old_count, 0) + incr;
* sem->count = tmp;
* return old_count;
*/
static inline int __sem_update_count(struct semaphore *sem, int incr)
{
int old_count, tmp;
__asm__ __volatile__("\n"
" ! __sem_update_count old_count(%0) tmp(%1) incr(%4) &sem->count(%3)\n"
"1: ldsw [%3], %0\n"
" mov %0, %1\n"
" cmp %0, 0\n"
" movl %%icc, 0, %1\n"
" add %1, %4, %1\n"
" cas [%3], %0, %1\n"
" cmp %0, %1\n"
" membar #StoreLoad | #StoreStore\n"
" bne,pn %%icc, 1b\n"
" nop\n"
: "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
: "r" (&sem->count), "r" (incr), "m" (sem->count)
: "cc");
return old_count;
}
static void __up(struct semaphore *sem)
{
__sem_update_count(sem, 1);
wake_up(&sem->wait);
}
void up(struct semaphore *sem)
{
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count + 1;
* sem->count = new_val;
* if (old_val < 0)
* __up(sem);
*
* The (old_val < 0) test is equivalent to
* the more straightforward (new_val <= 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! up sem(%0)\n"
" membar #StoreLoad | #LoadLoad\n"
"1: lduw [%0], %%g1\n"
" add %%g1, 1, %%g7\n"
" cas [%0], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" addcc %%g7, 1, %%g0\n"
" membar #StoreLoad | #StoreStore\n"
" ble,pn %%icc, 3f\n"
" nop\n"
"2:\n"
" .subsection 2\n"
"3: mov %0, %%g1\n"
" save %%sp, -160, %%sp\n"
" call %1\n"
" mov %%g1, %%o0\n"
" ba,pt %%xcc, 2b\n"
" restore\n"
" .previous\n"
: : "r" (sem), "i" (__up)
: "g1", "g2", "g3", "g7", "memory", "cc");
}
static void __sched __down(struct semaphore * sem)
{
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
tsk->state = TASK_UNINTERRUPTIBLE;
add_wait_queue_exclusive(&sem->wait, &wait);
while (__sem_update_count(sem, -1) <= 0) {
schedule();
tsk->state = TASK_UNINTERRUPTIBLE;
}
remove_wait_queue(&sem->wait, &wait);
tsk->state = TASK_RUNNING;
wake_up(&sem->wait);
}
void __sched down(struct semaphore *sem)
{
might_sleep();
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count - 1;
* sem->count = new_val;
* if (old_val < 1)
* __down(sem);
*
* The (old_val < 1) test is equivalent to
* the more straightforward (new_val < 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! down sem(%0)\n"
"1: lduw [%0], %%g1\n"
" sub %%g1, 1, %%g7\n"
" cas [%0], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" cmp %%g7, 1\n"
" membar #StoreLoad | #StoreStore\n"
" bl,pn %%icc, 3f\n"
" nop\n"
"2:\n"
" .subsection 2\n"
"3: mov %0, %%g1\n"
" save %%sp, -160, %%sp\n"
" call %1\n"
" mov %%g1, %%o0\n"
" ba,pt %%xcc, 2b\n"
" restore\n"
" .previous\n"
: : "r" (sem), "i" (__down)
: "g1", "g2", "g3", "g7", "memory", "cc");
}
int down_trylock(struct semaphore *sem)
{
int ret;
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count - 1;
* if (old_val < 1) {
* ret = 1;
* } else {
* sem->count = new_val;
* ret = 0;
* }
*
* The (old_val < 1) test is equivalent to
* the more straightforward (new_val < 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! down_trylock sem(%1) ret(%0)\n"
"1: lduw [%1], %%g1\n"
" sub %%g1, 1, %%g7\n"
" cmp %%g1, 1\n"
" bl,pn %%icc, 2f\n"
" mov 1, %0\n"
" cas [%1], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" mov 0, %0\n"
" membar #StoreLoad | #StoreStore\n"
"2:\n"
: "=&r" (ret)
: "r" (sem)
: "g1", "g7", "memory", "cc");
return ret;
}
static int __sched __down_interruptible(struct semaphore * sem)
{
int retval = 0;
struct task_struct *tsk = current;
DECLARE_WAITQUEUE(wait, tsk);
tsk->state = TASK_INTERRUPTIBLE;
add_wait_queue_exclusive(&sem->wait, &wait);
while (__sem_update_count(sem, -1) <= 0) {
if (signal_pending(current)) {
__sem_update_count(sem, 0);
retval = -EINTR;
break;
}
schedule();
tsk->state = TASK_INTERRUPTIBLE;
}
tsk->state = TASK_RUNNING;
remove_wait_queue(&sem->wait, &wait);
wake_up(&sem->wait);
return retval;
}
int __sched down_interruptible(struct semaphore *sem)
{
int ret = 0;
might_sleep();
/* This atomically does:
* old_val = sem->count;
* new_val = sem->count - 1;
* sem->count = new_val;
* if (old_val < 1)
* ret = __down_interruptible(sem);
*
* The (old_val < 1) test is equivalent to
* the more straightforward (new_val < 0),
* but it is easier to test the former because
* of how the CAS instruction works.
*/
__asm__ __volatile__("\n"
" ! down_interruptible sem(%2) ret(%0)\n"
"1: lduw [%2], %%g1\n"
" sub %%g1, 1, %%g7\n"
" cas [%2], %%g1, %%g7\n"
" cmp %%g1, %%g7\n"
" bne,pn %%icc, 1b\n"
" cmp %%g7, 1\n"
" membar #StoreLoad | #StoreStore\n"
" bl,pn %%icc, 3f\n"
" nop\n"
"2:\n"
" .subsection 2\n"
"3: mov %2, %%g1\n"
" save %%sp, -160, %%sp\n"
" call %3\n"
" mov %%g1, %%o0\n"
" ba,pt %%xcc, 2b\n"
" restore\n"
" .previous\n"
: "=r" (ret)
: "0" (ret), "r" (sem), "i" (__down_interruptible)
: "g1", "g2", "g3", "g7", "memory", "cc");
return ret;
}
|
