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Diffstat (limited to 'lib/semaphore-sleepers.c')
-rw-r--r-- | lib/semaphore-sleepers.c | 176 |
1 files changed, 0 insertions, 176 deletions
diff --git a/lib/semaphore-sleepers.c b/lib/semaphore-sleepers.c deleted file mode 100644 index 0198782cdacb..000000000000 --- a/lib/semaphore-sleepers.c +++ /dev/null | |||
@@ -1,176 +0,0 @@ | |||
1 | /* | ||
2 | * i386 and x86-64 semaphore implementation. | ||
3 | * | ||
4 | * (C) Copyright 1999 Linus Torvalds | ||
5 | * | ||
6 | * Portions Copyright 1999 Red Hat, Inc. | ||
7 | * | ||
8 | * This program is free software; you can redistribute it and/or | ||
9 | * modify it under the terms of the GNU General Public License | ||
10 | * as published by the Free Software Foundation; either version | ||
11 | * 2 of the License, or (at your option) any later version. | ||
12 | * | ||
13 | * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org> | ||
14 | */ | ||
15 | #include <linux/sched.h> | ||
16 | #include <linux/err.h> | ||
17 | #include <linux/init.h> | ||
18 | #include <asm/semaphore.h> | ||
19 | |||
20 | /* | ||
21 | * Semaphores are implemented using a two-way counter: | ||
22 | * The "count" variable is decremented for each process | ||
23 | * that tries to acquire the semaphore, while the "sleeping" | ||
24 | * variable is a count of such acquires. | ||
25 | * | ||
26 | * Notably, the inline "up()" and "down()" functions can | ||
27 | * efficiently test if they need to do any extra work (up | ||
28 | * needs to do something only if count was negative before | ||
29 | * the increment operation. | ||
30 | * | ||
31 | * "sleeping" and the contention routine ordering is protected | ||
32 | * by the spinlock in the semaphore's waitqueue head. | ||
33 | * | ||
34 | * Note that these functions are only called when there is | ||
35 | * contention on the lock, and as such all this is the | ||
36 | * "non-critical" part of the whole semaphore business. The | ||
37 | * critical part is the inline stuff in <asm/semaphore.h> | ||
38 | * where we want to avoid any extra jumps and calls. | ||
39 | */ | ||
40 | |||
41 | /* | ||
42 | * Logic: | ||
43 | * - only on a boundary condition do we need to care. When we go | ||
44 | * from a negative count to a non-negative, we wake people up. | ||
45 | * - when we go from a non-negative count to a negative do we | ||
46 | * (a) synchronize with the "sleeper" count and (b) make sure | ||
47 | * that we're on the wakeup list before we synchronize so that | ||
48 | * we cannot lose wakeup events. | ||
49 | */ | ||
50 | |||
51 | void __up(struct semaphore *sem) | ||
52 | { | ||
53 | wake_up(&sem->wait); | ||
54 | } | ||
55 | |||
56 | void __sched __down(struct semaphore *sem) | ||
57 | { | ||
58 | struct task_struct *tsk = current; | ||
59 | DECLARE_WAITQUEUE(wait, tsk); | ||
60 | unsigned long flags; | ||
61 | |||
62 | tsk->state = TASK_UNINTERRUPTIBLE; | ||
63 | spin_lock_irqsave(&sem->wait.lock, flags); | ||
64 | add_wait_queue_exclusive_locked(&sem->wait, &wait); | ||
65 | |||
66 | sem->sleepers++; | ||
67 | for (;;) { | ||
68 | int sleepers = sem->sleepers; | ||
69 | |||
70 | /* | ||
71 | * Add "everybody else" into it. They aren't | ||
72 | * playing, because we own the spinlock in | ||
73 | * the wait_queue_head. | ||
74 | */ | ||
75 | if (!atomic_add_negative(sleepers - 1, &sem->count)) { | ||
76 | sem->sleepers = 0; | ||
77 | break; | ||
78 | } | ||
79 | sem->sleepers = 1; /* us - see -1 above */ | ||
80 | spin_unlock_irqrestore(&sem->wait.lock, flags); | ||
81 | |||
82 | schedule(); | ||
83 | |||
84 | spin_lock_irqsave(&sem->wait.lock, flags); | ||
85 | tsk->state = TASK_UNINTERRUPTIBLE; | ||
86 | } | ||
87 | remove_wait_queue_locked(&sem->wait, &wait); | ||
88 | wake_up_locked(&sem->wait); | ||
89 | spin_unlock_irqrestore(&sem->wait.lock, flags); | ||
90 | tsk->state = TASK_RUNNING; | ||
91 | } | ||
92 | |||
93 | int __sched __down_interruptible(struct semaphore *sem) | ||
94 | { | ||
95 | int retval = 0; | ||
96 | struct task_struct *tsk = current; | ||
97 | DECLARE_WAITQUEUE(wait, tsk); | ||
98 | unsigned long flags; | ||
99 | |||
100 | tsk->state = TASK_INTERRUPTIBLE; | ||
101 | spin_lock_irqsave(&sem->wait.lock, flags); | ||
102 | add_wait_queue_exclusive_locked(&sem->wait, &wait); | ||
103 | |||
104 | sem->sleepers++; | ||
105 | for (;;) { | ||
106 | int sleepers = sem->sleepers; | ||
107 | |||
108 | /* | ||
109 | * With signals pending, this turns into | ||
110 | * the trylock failure case - we won't be | ||
111 | * sleeping, and we* can't get the lock as | ||
112 | * it has contention. Just correct the count | ||
113 | * and exit. | ||
114 | */ | ||
115 | if (signal_pending(current)) { | ||
116 | retval = -EINTR; | ||
117 | sem->sleepers = 0; | ||
118 | atomic_add(sleepers, &sem->count); | ||
119 | break; | ||
120 | } | ||
121 | |||
122 | /* | ||
123 | * Add "everybody else" into it. They aren't | ||
124 | * playing, because we own the spinlock in | ||
125 | * wait_queue_head. The "-1" is because we're | ||
126 | * still hoping to get the semaphore. | ||
127 | */ | ||
128 | if (!atomic_add_negative(sleepers - 1, &sem->count)) { | ||
129 | sem->sleepers = 0; | ||
130 | break; | ||
131 | } | ||
132 | sem->sleepers = 1; /* us - see -1 above */ | ||
133 | spin_unlock_irqrestore(&sem->wait.lock, flags); | ||
134 | |||
135 | schedule(); | ||
136 | |||
137 | spin_lock_irqsave(&sem->wait.lock, flags); | ||
138 | tsk->state = TASK_INTERRUPTIBLE; | ||
139 | } | ||
140 | remove_wait_queue_locked(&sem->wait, &wait); | ||
141 | wake_up_locked(&sem->wait); | ||
142 | spin_unlock_irqrestore(&sem->wait.lock, flags); | ||
143 | |||
144 | tsk->state = TASK_RUNNING; | ||
145 | return retval; | ||
146 | } | ||
147 | |||
148 | /* | ||
149 | * Trylock failed - make sure we correct for | ||
150 | * having decremented the count. | ||
151 | * | ||
152 | * We could have done the trylock with a | ||
153 | * single "cmpxchg" without failure cases, | ||
154 | * but then it wouldn't work on a 386. | ||
155 | */ | ||
156 | int __down_trylock(struct semaphore *sem) | ||
157 | { | ||
158 | int sleepers; | ||
159 | unsigned long flags; | ||
160 | |||
161 | spin_lock_irqsave(&sem->wait.lock, flags); | ||
162 | sleepers = sem->sleepers + 1; | ||
163 | sem->sleepers = 0; | ||
164 | |||
165 | /* | ||
166 | * Add "everybody else" and us into it. They aren't | ||
167 | * playing, because we own the spinlock in the | ||
168 | * wait_queue_head. | ||
169 | */ | ||
170 | if (!atomic_add_negative(sleepers, &sem->count)) { | ||
171 | wake_up_locked(&sem->wait); | ||
172 | } | ||
173 | |||
174 | spin_unlock_irqrestore(&sem->wait.lock, flags); | ||
175 | return 1; | ||
176 | } | ||