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1da177e4 LT |
1 | /* $Id: semaphore.c,v 1.9 2001/11/18 00:12:56 davem Exp $ |
2 | * semaphore.c: Sparc64 semaphore implementation. | |
3 | * | |
4 | * This is basically the PPC semaphore scheme ported to use | |
5 | * the sparc64 atomic instructions, so see the PPC code for | |
6 | * credits. | |
7 | */ | |
8 | ||
9 | #include <linux/sched.h> | |
10 | #include <linux/errno.h> | |
11 | #include <linux/init.h> | |
12 | ||
13 | /* | |
14 | * Atomically update sem->count. | |
15 | * This does the equivalent of the following: | |
16 | * | |
17 | * old_count = sem->count; | |
18 | * tmp = MAX(old_count, 0) + incr; | |
19 | * sem->count = tmp; | |
20 | * return old_count; | |
21 | */ | |
22 | static __inline__ int __sem_update_count(struct semaphore *sem, int incr) | |
23 | { | |
24 | int old_count, tmp; | |
25 | ||
26 | __asm__ __volatile__("\n" | |
27 | " ! __sem_update_count old_count(%0) tmp(%1) incr(%4) &sem->count(%3)\n" | |
28 | "1: ldsw [%3], %0\n" | |
29 | " mov %0, %1\n" | |
30 | " cmp %0, 0\n" | |
31 | " movl %%icc, 0, %1\n" | |
32 | " add %1, %4, %1\n" | |
33 | " cas [%3], %0, %1\n" | |
34 | " cmp %0, %1\n" | |
35 | " bne,pn %%icc, 1b\n" | |
36 | " membar #StoreLoad | #StoreStore\n" | |
37 | : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count) | |
38 | : "r" (&sem->count), "r" (incr), "m" (sem->count) | |
39 | : "cc"); | |
40 | ||
41 | return old_count; | |
42 | } | |
43 | ||
44 | static void __up(struct semaphore *sem) | |
45 | { | |
46 | __sem_update_count(sem, 1); | |
47 | wake_up(&sem->wait); | |
48 | } | |
49 | ||
50 | void up(struct semaphore *sem) | |
51 | { | |
52 | /* This atomically does: | |
53 | * old_val = sem->count; | |
54 | * new_val = sem->count + 1; | |
55 | * sem->count = new_val; | |
56 | * if (old_val < 0) | |
57 | * __up(sem); | |
58 | * | |
59 | * The (old_val < 0) test is equivalent to | |
60 | * the more straightforward (new_val <= 0), | |
61 | * but it is easier to test the former because | |
62 | * of how the CAS instruction works. | |
63 | */ | |
64 | ||
65 | __asm__ __volatile__("\n" | |
66 | " ! up sem(%0)\n" | |
67 | " membar #StoreLoad | #LoadLoad\n" | |
68 | "1: lduw [%0], %%g1\n" | |
69 | " add %%g1, 1, %%g7\n" | |
70 | " cas [%0], %%g1, %%g7\n" | |
71 | " cmp %%g1, %%g7\n" | |
72 | " bne,pn %%icc, 1b\n" | |
73 | " addcc %%g7, 1, %%g0\n" | |
74 | " ble,pn %%icc, 3f\n" | |
75 | " membar #StoreLoad | #StoreStore\n" | |
76 | "2:\n" | |
77 | " .subsection 2\n" | |
78 | "3: mov %0, %%g1\n" | |
79 | " save %%sp, -160, %%sp\n" | |
80 | " call %1\n" | |
81 | " mov %%g1, %%o0\n" | |
82 | " ba,pt %%xcc, 2b\n" | |
83 | " restore\n" | |
84 | " .previous\n" | |
85 | : : "r" (sem), "i" (__up) | |
86 | : "g1", "g2", "g3", "g7", "memory", "cc"); | |
87 | } | |
88 | ||
89 | static void __sched __down(struct semaphore * sem) | |
90 | { | |
91 | struct task_struct *tsk = current; | |
92 | DECLARE_WAITQUEUE(wait, tsk); | |
93 | ||
94 | tsk->state = TASK_UNINTERRUPTIBLE; | |
95 | add_wait_queue_exclusive(&sem->wait, &wait); | |
96 | ||
97 | while (__sem_update_count(sem, -1) <= 0) { | |
98 | schedule(); | |
99 | tsk->state = TASK_UNINTERRUPTIBLE; | |
100 | } | |
101 | remove_wait_queue(&sem->wait, &wait); | |
102 | tsk->state = TASK_RUNNING; | |
103 | ||
104 | wake_up(&sem->wait); | |
105 | } | |
106 | ||
107 | void __sched down(struct semaphore *sem) | |
108 | { | |
109 | might_sleep(); | |
110 | /* This atomically does: | |
111 | * old_val = sem->count; | |
112 | * new_val = sem->count - 1; | |
113 | * sem->count = new_val; | |
114 | * if (old_val < 1) | |
115 | * __down(sem); | |
116 | * | |
117 | * The (old_val < 1) test is equivalent to | |
118 | * the more straightforward (new_val < 0), | |
119 | * but it is easier to test the former because | |
120 | * of how the CAS instruction works. | |
121 | */ | |
122 | ||
123 | __asm__ __volatile__("\n" | |
124 | " ! down sem(%0)\n" | |
125 | "1: lduw [%0], %%g1\n" | |
126 | " sub %%g1, 1, %%g7\n" | |
127 | " cas [%0], %%g1, %%g7\n" | |
128 | " cmp %%g1, %%g7\n" | |
129 | " bne,pn %%icc, 1b\n" | |
130 | " cmp %%g7, 1\n" | |
131 | " bl,pn %%icc, 3f\n" | |
132 | " membar #StoreLoad | #StoreStore\n" | |
133 | "2:\n" | |
134 | " .subsection 2\n" | |
135 | "3: mov %0, %%g1\n" | |
136 | " save %%sp, -160, %%sp\n" | |
137 | " call %1\n" | |
138 | " mov %%g1, %%o0\n" | |
139 | " ba,pt %%xcc, 2b\n" | |
140 | " restore\n" | |
141 | " .previous\n" | |
142 | : : "r" (sem), "i" (__down) | |
143 | : "g1", "g2", "g3", "g7", "memory", "cc"); | |
144 | } | |
145 | ||
146 | int down_trylock(struct semaphore *sem) | |
147 | { | |
148 | int ret; | |
149 | ||
150 | /* This atomically does: | |
151 | * old_val = sem->count; | |
152 | * new_val = sem->count - 1; | |
153 | * if (old_val < 1) { | |
154 | * ret = 1; | |
155 | * } else { | |
156 | * sem->count = new_val; | |
157 | * ret = 0; | |
158 | * } | |
159 | * | |
160 | * The (old_val < 1) test is equivalent to | |
161 | * the more straightforward (new_val < 0), | |
162 | * but it is easier to test the former because | |
163 | * of how the CAS instruction works. | |
164 | */ | |
165 | ||
166 | __asm__ __volatile__("\n" | |
167 | " ! down_trylock sem(%1) ret(%0)\n" | |
168 | "1: lduw [%1], %%g1\n" | |
169 | " sub %%g1, 1, %%g7\n" | |
170 | " cmp %%g1, 1\n" | |
171 | " bl,pn %%icc, 2f\n" | |
172 | " mov 1, %0\n" | |
173 | " cas [%1], %%g1, %%g7\n" | |
174 | " cmp %%g1, %%g7\n" | |
175 | " bne,pn %%icc, 1b\n" | |
176 | " mov 0, %0\n" | |
177 | " membar #StoreLoad | #StoreStore\n" | |
178 | "2:\n" | |
179 | : "=&r" (ret) | |
180 | : "r" (sem) | |
181 | : "g1", "g7", "memory", "cc"); | |
182 | ||
183 | return ret; | |
184 | } | |
185 | ||
186 | static int __sched __down_interruptible(struct semaphore * sem) | |
187 | { | |
188 | int retval = 0; | |
189 | struct task_struct *tsk = current; | |
190 | DECLARE_WAITQUEUE(wait, tsk); | |
191 | ||
192 | tsk->state = TASK_INTERRUPTIBLE; | |
193 | add_wait_queue_exclusive(&sem->wait, &wait); | |
194 | ||
195 | while (__sem_update_count(sem, -1) <= 0) { | |
196 | if (signal_pending(current)) { | |
197 | __sem_update_count(sem, 0); | |
198 | retval = -EINTR; | |
199 | break; | |
200 | } | |
201 | schedule(); | |
202 | tsk->state = TASK_INTERRUPTIBLE; | |
203 | } | |
204 | tsk->state = TASK_RUNNING; | |
205 | remove_wait_queue(&sem->wait, &wait); | |
206 | wake_up(&sem->wait); | |
207 | return retval; | |
208 | } | |
209 | ||
210 | int __sched down_interruptible(struct semaphore *sem) | |
211 | { | |
212 | int ret = 0; | |
213 | ||
214 | might_sleep(); | |
215 | /* This atomically does: | |
216 | * old_val = sem->count; | |
217 | * new_val = sem->count - 1; | |
218 | * sem->count = new_val; | |
219 | * if (old_val < 1) | |
220 | * ret = __down_interruptible(sem); | |
221 | * | |
222 | * The (old_val < 1) test is equivalent to | |
223 | * the more straightforward (new_val < 0), | |
224 | * but it is easier to test the former because | |
225 | * of how the CAS instruction works. | |
226 | */ | |
227 | ||
228 | __asm__ __volatile__("\n" | |
229 | " ! down_interruptible sem(%2) ret(%0)\n" | |
230 | "1: lduw [%2], %%g1\n" | |
231 | " sub %%g1, 1, %%g7\n" | |
232 | " cas [%2], %%g1, %%g7\n" | |
233 | " cmp %%g1, %%g7\n" | |
234 | " bne,pn %%icc, 1b\n" | |
235 | " cmp %%g7, 1\n" | |
236 | " bl,pn %%icc, 3f\n" | |
237 | " membar #StoreLoad | #StoreStore\n" | |
238 | "2:\n" | |
239 | " .subsection 2\n" | |
240 | "3: mov %2, %%g1\n" | |
241 | " save %%sp, -160, %%sp\n" | |
242 | " call %3\n" | |
243 | " mov %%g1, %%o0\n" | |
244 | " ba,pt %%xcc, 2b\n" | |
245 | " restore\n" | |
246 | " .previous\n" | |
247 | : "=r" (ret) | |
248 | : "0" (ret), "r" (sem), "i" (__down_interruptible) | |
249 | : "g1", "g2", "g3", "g7", "memory", "cc"); | |
250 | return ret; | |
251 | } |