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Linux kernel mirror (for testing)
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1/* SMP- and interrupt-safe semaphores.
2 * PA-RISC version by Matthew Wilcox
3 *
4 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
5 * Copyright (C) 1996 Linus Torvalds
6 * Copyright (C) 1999-2001 Matthew Wilcox < willy at debian d0T org >
7 * Copyright (C) 2000 Grant Grundler < grundler a debian org >
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 */
23
24#ifndef _ASM_PARISC_SEMAPHORE_H
25#define _ASM_PARISC_SEMAPHORE_H
26
27#include <linux/spinlock.h>
28#include <linux/wait.h>
29#include <linux/rwsem.h>
30
31#include <asm/system.h>
32
33/*
34 * The `count' is initialised to the number of people who are allowed to
35 * take the lock. (Normally we want a mutex, so this is `1'). if
36 * `count' is positive, the lock can be taken. if it's 0, no-one is
37 * waiting on it. if it's -1, at least one task is waiting.
38 */
39struct semaphore {
40 spinlock_t sentry;
41 int count;
42 wait_queue_head_t wait;
43};
44
45#define __SEMAPHORE_INITIALIZER(name, n) \
46{ \
47 .sentry = SPIN_LOCK_UNLOCKED, \
48 .count = n, \
49 .wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
50}
51
52#define __MUTEX_INITIALIZER(name) \
53 __SEMAPHORE_INITIALIZER(name,1)
54
55#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
56 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
57
58#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
59#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
60
61extern inline void sema_init (struct semaphore *sem, int val)
62{
63 *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
64}
65
66static inline void init_MUTEX (struct semaphore *sem)
67{
68 sema_init(sem, 1);
69}
70
71static inline void init_MUTEX_LOCKED (struct semaphore *sem)
72{
73 sema_init(sem, 0);
74}
75
76static inline int sem_getcount(struct semaphore *sem)
77{
78 return sem->count;
79}
80
81asmlinkage void __down(struct semaphore * sem);
82asmlinkage int __down_interruptible(struct semaphore * sem);
83asmlinkage void __up(struct semaphore * sem);
84
85/* Semaphores can be `tried' from irq context. So we have to disable
86 * interrupts while we're messing with the semaphore. Sorry.
87 */
88
89extern __inline__ void down(struct semaphore * sem)
90{
91 might_sleep();
92 spin_lock_irq(&sem->sentry);
93 if (sem->count > 0) {
94 sem->count--;
95 } else {
96 __down(sem);
97 }
98 spin_unlock_irq(&sem->sentry);
99}
100
101extern __inline__ int down_interruptible(struct semaphore * sem)
102{
103 int ret = 0;
104 might_sleep();
105 spin_lock_irq(&sem->sentry);
106 if (sem->count > 0) {
107 sem->count--;
108 } else {
109 ret = __down_interruptible(sem);
110 }
111 spin_unlock_irq(&sem->sentry);
112 return ret;
113}
114
115/*
116 * down_trylock returns 0 on success, 1 if we failed to get the lock.
117 * May not sleep, but must preserve irq state
118 */
119extern __inline__ int down_trylock(struct semaphore * sem)
120{
121 int flags, count;
122
123 spin_lock_irqsave(&sem->sentry, flags);
124 count = sem->count - 1;
125 if (count >= 0)
126 sem->count = count;
127 spin_unlock_irqrestore(&sem->sentry, flags);
128 return (count < 0);
129}
130
131/*
132 * Note! This is subtle. We jump to wake people up only if
133 * the semaphore was negative (== somebody was waiting on it).
134 */
135extern __inline__ void up(struct semaphore * sem)
136{
137 int flags;
138 spin_lock_irqsave(&sem->sentry, flags);
139 if (sem->count < 0) {
140 __up(sem);
141 } else {
142 sem->count++;
143 }
144 spin_unlock_irqrestore(&sem->sentry, flags);
145}
146
147#endif /* _ASM_PARISC_SEMAPHORE_H */