[PATCH] arch/alpha/kernel/machvec_impl.h: C99 struct initializer
[linux-2.6] / arch / alpha / kernel / semaphore.c
1 /*
2  * Alpha semaphore implementation.
3  *
4  * (C) Copyright 1996 Linus Torvalds
5  * (C) Copyright 1999, 2000 Richard Henderson
6  */
7
8 #include <linux/errno.h>
9 #include <linux/sched.h>
10 #include <linux/init.h>
11
12 /*
13  * This is basically the PPC semaphore scheme ported to use
14  * the Alpha ll/sc sequences, so see the PPC code for
15  * credits.
16  */
17
18 /*
19  * Atomically update sem->count.
20  * This does the equivalent of the following:
21  *
22  *      old_count = sem->count;
23  *      tmp = MAX(old_count, 0) + incr;
24  *      sem->count = tmp;
25  *      return old_count;
26  */
27 static inline int __sem_update_count(struct semaphore *sem, int incr)
28 {
29         long old_count, tmp = 0;
30
31         __asm__ __volatile__(
32         "1:     ldl_l   %0,%2\n"
33         "       cmovgt  %0,%0,%1\n"
34         "       addl    %1,%3,%1\n"
35         "       stl_c   %1,%2\n"
36         "       beq     %1,2f\n"
37         "       mb\n"
38         ".subsection 2\n"
39         "2:     br      1b\n"
40         ".previous"
41         : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
42         : "Ir" (incr), "1" (tmp), "m" (sem->count));
43
44         return old_count;
45 }
46
47 /*
48  * Perform the "down" function.  Return zero for semaphore acquired,
49  * return negative for signalled out of the function.
50  *
51  * If called from down, the return is ignored and the wait loop is
52  * not interruptible.  This means that a task waiting on a semaphore
53  * using "down()" cannot be killed until someone does an "up()" on
54  * the semaphore.
55  *
56  * If called from down_interruptible, the return value gets checked
57  * upon return.  If the return value is negative then the task continues
58  * with the negative value in the return register (it can be tested by
59  * the caller).
60  *
61  * Either form may be used in conjunction with "up()".
62  */
63
64 void __sched
65 __down_failed(struct semaphore *sem)
66 {
67         struct task_struct *tsk = current;
68         DECLARE_WAITQUEUE(wait, tsk);
69
70 #ifdef CONFIG_DEBUG_SEMAPHORE
71         printk("%s(%d): down failed(%p)\n",
72                tsk->comm, tsk->pid, sem);
73 #endif
74
75         tsk->state = TASK_UNINTERRUPTIBLE;
76         wmb();
77         add_wait_queue_exclusive(&sem->wait, &wait);
78
79         /*
80          * Try to get the semaphore.  If the count is > 0, then we've
81          * got the semaphore; we decrement count and exit the loop.
82          * If the count is 0 or negative, we set it to -1, indicating
83          * that we are asleep, and then sleep.
84          */
85         while (__sem_update_count(sem, -1) <= 0) {
86                 schedule();
87                 set_task_state(tsk, TASK_UNINTERRUPTIBLE);
88         }
89         remove_wait_queue(&sem->wait, &wait);
90         tsk->state = TASK_RUNNING;
91
92         /*
93          * If there are any more sleepers, wake one of them up so
94          * that it can either get the semaphore, or set count to -1
95          * indicating that there are still processes sleeping.
96          */
97         wake_up(&sem->wait);
98
99 #ifdef CONFIG_DEBUG_SEMAPHORE
100         printk("%s(%d): down acquired(%p)\n",
101                tsk->comm, tsk->pid, sem);
102 #endif
103 }
104
105 int __sched
106 __down_failed_interruptible(struct semaphore *sem)
107 {
108         struct task_struct *tsk = current;
109         DECLARE_WAITQUEUE(wait, tsk);
110         long ret = 0;
111
112 #ifdef CONFIG_DEBUG_SEMAPHORE
113         printk("%s(%d): down failed(%p)\n",
114                tsk->comm, tsk->pid, sem);
115 #endif
116
117         tsk->state = TASK_INTERRUPTIBLE;
118         wmb();
119         add_wait_queue_exclusive(&sem->wait, &wait);
120
121         while (__sem_update_count(sem, -1) <= 0) {
122                 if (signal_pending(current)) {
123                         /*
124                          * A signal is pending - give up trying.
125                          * Set sem->count to 0 if it is negative,
126                          * since we are no longer sleeping.
127                          */
128                         __sem_update_count(sem, 0);
129                         ret = -EINTR;
130                         break;
131                 }
132                 schedule();
133                 set_task_state(tsk, TASK_INTERRUPTIBLE);
134         }
135
136         remove_wait_queue(&sem->wait, &wait);
137         tsk->state = TASK_RUNNING;
138         wake_up(&sem->wait);
139
140 #ifdef CONFIG_DEBUG_SEMAPHORE
141         printk("%s(%d): down %s(%p)\n",
142                current->comm, current->pid,
143                (ret < 0 ? "interrupted" : "acquired"), sem);
144 #endif
145         return ret;
146 }
147
148 void
149 __up_wakeup(struct semaphore *sem)
150 {
151         /*
152          * Note that we incremented count in up() before we came here,
153          * but that was ineffective since the result was <= 0, and
154          * any negative value of count is equivalent to 0.
155          * This ends up setting count to 1, unless count is now > 0
156          * (i.e. because some other cpu has called up() in the meantime),
157          * in which case we just increment count.
158          */
159         __sem_update_count(sem, 1);
160         wake_up(&sem->wait);
161 }
162
163 void __sched
164 down(struct semaphore *sem)
165 {
166 #ifdef WAITQUEUE_DEBUG
167         CHECK_MAGIC(sem->__magic);
168 #endif
169 #ifdef CONFIG_DEBUG_SEMAPHORE
170         printk("%s(%d): down(%p) <count=%d> from %p\n",
171                current->comm, current->pid, sem,
172                atomic_read(&sem->count), __builtin_return_address(0));
173 #endif
174         __down(sem);
175 }
176
177 int __sched
178 down_interruptible(struct semaphore *sem)
179 {
180 #ifdef WAITQUEUE_DEBUG
181         CHECK_MAGIC(sem->__magic);
182 #endif
183 #ifdef CONFIG_DEBUG_SEMAPHORE
184         printk("%s(%d): down(%p) <count=%d> from %p\n",
185                current->comm, current->pid, sem,
186                atomic_read(&sem->count), __builtin_return_address(0));
187 #endif
188         return __down_interruptible(sem);
189 }
190
191 int
192 down_trylock(struct semaphore *sem)
193 {
194         int ret;
195
196 #ifdef WAITQUEUE_DEBUG
197         CHECK_MAGIC(sem->__magic);
198 #endif
199
200         ret = __down_trylock(sem);
201
202 #ifdef CONFIG_DEBUG_SEMAPHORE
203         printk("%s(%d): down_trylock %s from %p\n",
204                current->comm, current->pid,
205                ret ? "failed" : "acquired",
206                __builtin_return_address(0));
207 #endif
208
209         return ret;
210 }
211
212 void
213 up(struct semaphore *sem)
214 {
215 #ifdef WAITQUEUE_DEBUG
216         CHECK_MAGIC(sem->__magic);
217 #endif
218 #ifdef CONFIG_DEBUG_SEMAPHORE
219         printk("%s(%d): up(%p) <count=%d> from %p\n",
220                current->comm, current->pid, sem,
221                atomic_read(&sem->count), __builtin_return_address(0));
222 #endif
223         __up(sem);
224 }