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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/* 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070052#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
53 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
54
55#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
56#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
57
58extern inline void sema_init (struct semaphore *sem, int val)
59{
60 *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
61}
62
63static inline void init_MUTEX (struct semaphore *sem)
64{
65 sema_init(sem, 1);
66}
67
68static inline void init_MUTEX_LOCKED (struct semaphore *sem)
69{
70 sema_init(sem, 0);
71}
72
73static inline int sem_getcount(struct semaphore *sem)
74{
75 return sem->count;
76}
77
78asmlinkage void __down(struct semaphore * sem);
79asmlinkage int __down_interruptible(struct semaphore * sem);
80asmlinkage void __up(struct semaphore * sem);
81
82/* Semaphores can be `tried' from irq context. So we have to disable
83 * interrupts while we're messing with the semaphore. Sorry.
84 */
85
86extern __inline__ void down(struct semaphore * sem)
87{
88 might_sleep();
89 spin_lock_irq(&sem->sentry);
90 if (sem->count > 0) {
91 sem->count--;
92 } else {
93 __down(sem);
94 }
95 spin_unlock_irq(&sem->sentry);
96}
97
98extern __inline__ int down_interruptible(struct semaphore * sem)
99{
100 int ret = 0;
101 might_sleep();
102 spin_lock_irq(&sem->sentry);
103 if (sem->count > 0) {
104 sem->count--;
105 } else {
106 ret = __down_interruptible(sem);
107 }
108 spin_unlock_irq(&sem->sentry);
109 return ret;
110}
111
112/*
113 * down_trylock returns 0 on success, 1 if we failed to get the lock.
114 * May not sleep, but must preserve irq state
115 */
116extern __inline__ int down_trylock(struct semaphore * sem)
117{
118 int flags, count;
119
120 spin_lock_irqsave(&sem->sentry, flags);
121 count = sem->count - 1;
122 if (count >= 0)
123 sem->count = count;
124 spin_unlock_irqrestore(&sem->sentry, flags);
125 return (count < 0);
126}
127
128/*
129 * Note! This is subtle. We jump to wake people up only if
130 * the semaphore was negative (== somebody was waiting on it).
131 */
132extern __inline__ void up(struct semaphore * sem)
133{
134 int flags;
135 spin_lock_irqsave(&sem->sentry, flags);
136 if (sem->count < 0) {
137 __up(sem);
138 } else {
139 sem->count++;
140 }
141 spin_unlock_irqrestore(&sem->sentry, flags);
142}
143
144#endif /* _ASM_PARISC_SEMAPHORE_H */