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-rw-r--r--arch/sh64/kernel/semaphore.c140
1 files changed, 0 insertions, 140 deletions
diff --git a/arch/sh64/kernel/semaphore.c b/arch/sh64/kernel/semaphore.c
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index 72c16533436..00000000000
--- a/arch/sh64/kernel/semaphore.c
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1/*
2 * Just taken from alpha implementation.
3 * This can't work well, perhaps.
4 */
5/*
6 * Generic semaphore code. Buyer beware. Do your own
7 * specific changes in <asm/semaphore-helper.h>
8 */
9
10#include <linux/errno.h>
11#include <linux/rwsem.h>
12#include <linux/sched.h>
13#include <linux/wait.h>
14#include <linux/init.h>
15#include <asm/semaphore.h>
16#include <asm/semaphore-helper.h>
17
18spinlock_t semaphore_wake_lock;
19
20/*
21 * Semaphores are implemented using a two-way counter:
22 * The "count" variable is decremented for each process
23 * that tries to sleep, while the "waking" variable is
24 * incremented when the "up()" code goes to wake up waiting
25 * processes.
26 *
27 * Notably, the inline "up()" and "down()" functions can
28 * efficiently test if they need to do any extra work (up
29 * needs to do something only if count was negative before
30 * the increment operation.
31 *
32 * waking_non_zero() (from asm/semaphore.h) must execute
33 * atomically.
34 *
35 * When __up() is called, the count was negative before
36 * incrementing it, and we need to wake up somebody.
37 *
38 * This routine adds one to the count of processes that need to
39 * wake up and exit. ALL waiting processes actually wake up but
40 * only the one that gets to the "waking" field first will gate
41 * through and acquire the semaphore. The others will go back
42 * to sleep.
43 *
44 * Note that these functions are only called when there is
45 * contention on the lock, and as such all this is the
46 * "non-critical" part of the whole semaphore business. The
47 * critical part is the inline stuff in <asm/semaphore.h>
48 * where we want to avoid any extra jumps and calls.
49 */
50void __up(struct semaphore *sem)
51{
52 wake_one_more(sem);
53 wake_up(&sem->wait);
54}
55
56/*
57 * Perform the "down" function. Return zero for semaphore acquired,
58 * return negative for signalled out of the function.
59 *
60 * If called from __down, the return is ignored and the wait loop is
61 * not interruptible. This means that a task waiting on a semaphore
62 * using "down()" cannot be killed until someone does an "up()" on
63 * the semaphore.
64 *
65 * If called from __down_interruptible, the return value gets checked
66 * upon return. If the return value is negative then the task continues
67 * with the negative value in the return register (it can be tested by
68 * the caller).
69 *
70 * Either form may be used in conjunction with "up()".
71 *
72 */
73
74#define DOWN_VAR \
75 struct task_struct *tsk = current; \
76 wait_queue_t wait; \
77 init_waitqueue_entry(&wait, tsk);
78
79#define DOWN_HEAD(task_state) \
80 \
81 \
82 tsk->state = (task_state); \
83 add_wait_queue(&sem->wait, &wait); \
84 \
85 /* \
86 * Ok, we're set up. sem->count is known to be less than zero \
87 * so we must wait. \
88 * \
89 * We can let go the lock for purposes of waiting. \
90 * We re-acquire it after awaking so as to protect \
91 * all semaphore operations. \
92 * \
93 * If "up()" is called before we call waking_non_zero() then \
94 * we will catch it right away. If it is called later then \
95 * we will have to go through a wakeup cycle to catch it. \
96 * \
97 * Multiple waiters contend for the semaphore lock to see \
98 * who gets to gate through and who has to wait some more. \
99 */ \
100 for (;;) {
101
102#define DOWN_TAIL(task_state) \
103 tsk->state = (task_state); \
104 } \
105 tsk->state = TASK_RUNNING; \
106 remove_wait_queue(&sem->wait, &wait);
107
108void __sched __down(struct semaphore * sem)
109{
110 DOWN_VAR
111 DOWN_HEAD(TASK_UNINTERRUPTIBLE)
112 if (waking_non_zero(sem))
113 break;
114 schedule();
115 DOWN_TAIL(TASK_UNINTERRUPTIBLE)
116}
117
118int __sched __down_interruptible(struct semaphore * sem)
119{
120 int ret = 0;
121 DOWN_VAR
122 DOWN_HEAD(TASK_INTERRUPTIBLE)
123
124 ret = waking_non_zero_interruptible(sem, tsk);
125 if (ret)
126 {
127 if (ret == 1)
128 /* ret != 0 only if we get interrupted -arca */
129 ret = 0;
130 break;
131 }
132 schedule();
133 DOWN_TAIL(TASK_INTERRUPTIBLE)
134 return ret;
135}
136
137int __down_trylock(struct semaphore * sem)
138{
139 return waking_non_zero_trylock(sem);
140}