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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/h8300/kernel/semaphore.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/h8300/kernel/semaphore.c')
-rw-r--r--arch/h8300/kernel/semaphore.c133
1 files changed, 133 insertions, 0 deletions
diff --git a/arch/h8300/kernel/semaphore.c b/arch/h8300/kernel/semaphore.c
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index 000000000000..1ebb79baaa8c
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+++ b/arch/h8300/kernel/semaphore.c
@@ -0,0 +1,133 @@
1/*
2 * Generic semaphore code. Buyer beware. Do your own
3 * specific changes in <asm/semaphore-helper.h>
4 */
5
6#include <linux/config.h>
7#include <linux/sched.h>
8#include <linux/init.h>
9#include <asm/semaphore-helper.h>
10
11#ifndef CONFIG_RMW_INSNS
12spinlock_t semaphore_wake_lock;
13#endif
14
15/*
16 * Semaphores are implemented using a two-way counter:
17 * The "count" variable is decremented for each process
18 * that tries to sleep, while the "waking" variable is
19 * incremented when the "up()" code goes to wake up waiting
20 * processes.
21 *
22 * Notably, the inline "up()" and "down()" functions can
23 * efficiently test if they need to do any extra work (up
24 * needs to do something only if count was negative before
25 * the increment operation.
26 *
27 * waking_non_zero() (from asm/semaphore.h) must execute
28 * atomically.
29 *
30 * When __up() is called, the count was negative before
31 * incrementing it, and we need to wake up somebody.
32 *
33 * This routine adds one to the count of processes that need to
34 * wake up and exit. ALL waiting processes actually wake up but
35 * only the one that gets to the "waking" field first will gate
36 * through and acquire the semaphore. The others will go back
37 * to sleep.
38 *
39 * Note that these functions are only called when there is
40 * contention on the lock, and as such all this is the
41 * "non-critical" part of the whole semaphore business. The
42 * critical part is the inline stuff in <asm/semaphore.h>
43 * where we want to avoid any extra jumps and calls.
44 */
45void __up(struct semaphore *sem)
46{
47 wake_one_more(sem);
48 wake_up(&sem->wait);
49}
50
51/*
52 * Perform the "down" function. Return zero for semaphore acquired,
53 * return negative for signalled out of the function.
54 *
55 * If called from __down, the return is ignored and the wait loop is
56 * not interruptible. This means that a task waiting on a semaphore
57 * using "down()" cannot be killed until someone does an "up()" on
58 * the semaphore.
59 *
60 * If called from __down_interruptible, the return value gets checked
61 * upon return. If the return value is negative then the task continues
62 * with the negative value in the return register (it can be tested by
63 * the caller).
64 *
65 * Either form may be used in conjunction with "up()".
66 *
67 */
68
69
70#define DOWN_HEAD(task_state) \
71 \
72 \
73 current->state = (task_state); \
74 add_wait_queue(&sem->wait, &wait); \
75 \
76 /* \
77 * Ok, we're set up. sem->count is known to be less than zero \
78 * so we must wait. \
79 * \
80 * We can let go the lock for purposes of waiting. \
81 * We re-acquire it after awaking so as to protect \
82 * all semaphore operations. \
83 * \
84 * If "up()" is called before we call waking_non_zero() then \
85 * we will catch it right away. If it is called later then \
86 * we will have to go through a wakeup cycle to catch it. \
87 * \
88 * Multiple waiters contend for the semaphore lock to see \
89 * who gets to gate through and who has to wait some more. \
90 */ \
91 for (;;) {
92
93#define DOWN_TAIL(task_state) \
94 current->state = (task_state); \
95 } \
96 current->state = TASK_RUNNING; \
97 remove_wait_queue(&sem->wait, &wait);
98
99void __sched __down(struct semaphore * sem)
100{
101 DECLARE_WAITQUEUE(wait, current);
102
103 DOWN_HEAD(TASK_UNINTERRUPTIBLE)
104 if (waking_non_zero(sem))
105 break;
106 schedule();
107 DOWN_TAIL(TASK_UNINTERRUPTIBLE)
108}
109
110int __sched __down_interruptible(struct semaphore * sem)
111{
112 DECLARE_WAITQUEUE(wait, current);
113 int ret = 0;
114
115 DOWN_HEAD(TASK_INTERRUPTIBLE)
116
117 ret = waking_non_zero_interruptible(sem, current);
118 if (ret)
119 {
120 if (ret == 1)
121 /* ret != 0 only if we get interrupted -arca */
122 ret = 0;
123 break;
124 }
125 schedule();
126 DOWN_TAIL(TASK_INTERRUPTIBLE)
127 return ret;
128}
129
130int __down_trylock(struct semaphore * sem)
131{
132 return waking_non_zero_trylock(sem);
133}