source: cmedia/trunk/Include/Asm/semaphore.h

Last change on this file was 354, checked in by stevenhl, 17 years ago

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1/* $Id: semaphore.h,v 1.1 2000/04/23 14:55:29 ktk Exp $ */
2
3#ifndef _I386_SEMAPHORE_H
4#define _I386_SEMAPHORE_H
5
6/*
7 * SMP- and interrupt-safe semaphores..
8 *
9 * (C) Copyright 1996 Linus Torvalds
10 *
11 * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
12 * the original code and to make semaphore waits
13 * interruptible so that processes waiting on
14 * semaphores can be killed.
15 * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
16 * functions in asm/sempahore-helper.h while fixing a
17 * potential and subtle race discovered by Ulrich Schmid
18 * in down_interruptible(). Since I started to play here I
19 * also implemented the `trylock' semaphore operation.
20 * 1999-07-02 Artur Skawina <skawina@geocities.com>
21 * Optimized "0(ecx)" -> "(ecx)" (the assembler does not
22 * do this). Changed calling sequences from push/jmp to
23 * traditional call/ret.
24 *
25 * If you would like to see an analysis of this implementation, please
26 * ftp to gcom.com and download the file
27 * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
28 *
29 */
30
31#include <asm/atomic.h>
32#include <linux/spinlock.h>
33
34struct semaphore {
35 atomic_t count;
36 int sleepers;
37 void * wait;
38#if WAITQUEUE_DEBUG
39 long __magic;
40#endif
41};
42
43#if WAITQUEUE_DEBUG
44# define __SEM_DEBUG_INIT(name) \
45 , (int)&(name).__magic
46#else
47# define __SEM_DEBUG_INIT(name)
48#endif
49
50#define __SEMAPHORE_INITIALIZER(name,count) \
51{ ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
52 __SEM_DEBUG_INIT(name) }
53
54#define __MUTEX_INITIALIZER(name) \
55 __SEMAPHORE_INITIALIZER(name,1)
56
57#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
58 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
59
60#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
61#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
62
63extern void sema_init (struct semaphore *sem, int val);
64void init_MUTEX (struct semaphore *sem);
65void init_MUTEX_LOCKED (struct semaphore *sem);
66
67 void __down_failed(void /* special register calling convention */);
68 int __down_failed_interruptible(void /* params in registers */);
69 int __down_failed_trylock(void /* params in registers */);
70 void __up_wakeup(void /* special register calling convention */);
71
72 void __down(struct semaphore * sem);
73 int __down_interruptible(struct semaphore * sem);
74 int __down_trylock(struct semaphore * sem);
75 void __up(struct semaphore * sem);
76
77/*
78 * This is ugly, but we want the default case to fall through.
79 * "down_failed" is a special asm handler that calls the C
80 * routine that actually waits. See arch/i386/lib/semaphore.S
81 */
82extern void down(struct semaphore * sem);
83
84extern int down_interruptible(struct semaphore * sem);
85
86extern int down_trylock(struct semaphore * sem);
87
88/*
89 * Note! This is subtle. We jump to wake people up only if
90 * the semaphore was negative (== somebody was waiting on it).
91 * The default case (no contention) will result in NO
92 * jumps for both down() and up().
93 */
94extern void up(struct semaphore * sem);
95
96#endif
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