ia64/xen-unstable

view old/xenolinux-2.4.16-sparse/include/asm-xeno/semaphore.h @ 235:d7d0a23b2e07

bitkeeper revision 1.93 (3e5a4e6bkPheUp3x1uufN2MS3LAB7A)

Latest and Greatest version of XenoLinux based on the Linux-2.4.21-pre4
kernel.
author iap10@labyrinth.cl.cam.ac.uk
date Mon Feb 24 16:55:07 2003 +0000 (2003-02-24)
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1 #ifndef _I386_SEMAPHORE_H
2 #define _I386_SEMAPHORE_H
4 #include <linux/linkage.h>
6 #ifdef __KERNEL__
8 /*
9 * SMP- and interrupt-safe semaphores..
10 *
11 * (C) Copyright 1996 Linus Torvalds
12 *
13 * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
14 * the original code and to make semaphore waits
15 * interruptible so that processes waiting on
16 * semaphores can be killed.
17 * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
18 * functions in asm/sempahore-helper.h while fixing a
19 * potential and subtle race discovered by Ulrich Schmid
20 * in down_interruptible(). Since I started to play here I
21 * also implemented the `trylock' semaphore operation.
22 * 1999-07-02 Artur Skawina <skawina@geocities.com>
23 * Optimized "0(ecx)" -> "(ecx)" (the assembler does not
24 * do this). Changed calling sequences from push/jmp to
25 * traditional call/ret.
26 * Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
27 * Some hacks to ensure compatibility with recent
28 * GCC snapshots, to avoid stack corruption when compiling
29 * with -fomit-frame-pointer. It's not sure if this will
30 * be fixed in GCC, as our previous implementation was a
31 * bit dubious.
32 *
33 * If you would like to see an analysis of this implementation, please
34 * ftp to gcom.com and download the file
35 * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
36 *
37 */
39 #include <asm/system.h>
40 #include <asm/atomic.h>
41 #include <linux/wait.h>
42 #include <linux/rwsem.h>
44 struct semaphore {
45 atomic_t count;
46 int sleepers;
47 wait_queue_head_t wait;
48 #if WAITQUEUE_DEBUG
49 long __magic;
50 #endif
51 };
53 #if WAITQUEUE_DEBUG
54 # define __SEM_DEBUG_INIT(name) \
55 , (int)&(name).__magic
56 #else
57 # define __SEM_DEBUG_INIT(name)
58 #endif
60 #define __SEMAPHORE_INITIALIZER(name,count) \
61 { ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
62 __SEM_DEBUG_INIT(name) }
64 #define __MUTEX_INITIALIZER(name) \
65 __SEMAPHORE_INITIALIZER(name,1)
67 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
68 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
70 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
71 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
73 static inline void sema_init (struct semaphore *sem, int val)
74 {
75 /*
76 * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
77 *
78 * i'd rather use the more flexible initialization above, but sadly
79 * GCC 2.7.2.3 emits a bogus warning. EGCS doesnt. Oh well.
80 */
81 atomic_set(&sem->count, val);
82 sem->sleepers = 0;
83 init_waitqueue_head(&sem->wait);
84 #if WAITQUEUE_DEBUG
85 sem->__magic = (int)&sem->__magic;
86 #endif
87 }
89 static inline void init_MUTEX (struct semaphore *sem)
90 {
91 sema_init(sem, 1);
92 }
94 static inline void init_MUTEX_LOCKED (struct semaphore *sem)
95 {
96 sema_init(sem, 0);
97 }
99 asmlinkage void __down_failed(void /* special register calling convention */);
100 asmlinkage int __down_failed_interruptible(void /* params in registers */);
101 asmlinkage int __down_failed_trylock(void /* params in registers */);
102 asmlinkage void __up_wakeup(void /* special register calling convention */);
104 asmlinkage void __down(struct semaphore * sem);
105 asmlinkage int __down_interruptible(struct semaphore * sem);
106 asmlinkage int __down_trylock(struct semaphore * sem);
107 asmlinkage void __up(struct semaphore * sem);
109 /*
110 * This is ugly, but we want the default case to fall through.
111 * "__down_failed" is a special asm handler that calls the C
112 * routine that actually waits. See arch/i386/kernel/semaphore.c
113 */
114 static inline void down(struct semaphore * sem)
115 {
116 #if WAITQUEUE_DEBUG
117 CHECK_MAGIC(sem->__magic);
118 #endif
120 __asm__ __volatile__(
121 "# atomic down operation\n\t"
122 LOCK "decl %0\n\t" /* --sem->count */
123 "js 2f\n"
124 "1:\n"
125 ".section .text.lock,\"ax\"\n"
126 "2:\tcall __down_failed\n\t"
127 "jmp 1b\n"
128 ".previous"
129 :"=m" (sem->count)
130 :"c" (sem)
131 :"memory");
132 }
134 /*
135 * Interruptible try to acquire a semaphore. If we obtained
136 * it, return zero. If we were interrupted, returns -EINTR
137 */
138 static inline int down_interruptible(struct semaphore * sem)
139 {
140 int result;
142 #if WAITQUEUE_DEBUG
143 CHECK_MAGIC(sem->__magic);
144 #endif
146 __asm__ __volatile__(
147 "# atomic interruptible down operation\n\t"
148 LOCK "decl %1\n\t" /* --sem->count */
149 "js 2f\n\t"
150 "xorl %0,%0\n"
151 "1:\n"
152 ".section .text.lock,\"ax\"\n"
153 "2:\tcall __down_failed_interruptible\n\t"
154 "jmp 1b\n"
155 ".previous"
156 :"=a" (result), "=m" (sem->count)
157 :"c" (sem)
158 :"memory");
159 return result;
160 }
162 /*
163 * Non-blockingly attempt to down() a semaphore.
164 * Returns zero if we acquired it
165 */
166 static inline int down_trylock(struct semaphore * sem)
167 {
168 int result;
170 #if WAITQUEUE_DEBUG
171 CHECK_MAGIC(sem->__magic);
172 #endif
174 __asm__ __volatile__(
175 "# atomic interruptible down operation\n\t"
176 LOCK "decl %1\n\t" /* --sem->count */
177 "js 2f\n\t"
178 "xorl %0,%0\n"
179 "1:\n"
180 ".section .text.lock,\"ax\"\n"
181 "2:\tcall __down_failed_trylock\n\t"
182 "jmp 1b\n"
183 ".previous"
184 :"=a" (result), "=m" (sem->count)
185 :"c" (sem)
186 :"memory");
187 return result;
188 }
190 /*
191 * Note! This is subtle. We jump to wake people up only if
192 * the semaphore was negative (== somebody was waiting on it).
193 * The default case (no contention) will result in NO
194 * jumps for both down() and up().
195 */
196 static inline void up(struct semaphore * sem)
197 {
198 #if WAITQUEUE_DEBUG
199 CHECK_MAGIC(sem->__magic);
200 #endif
201 __asm__ __volatile__(
202 "# atomic up operation\n\t"
203 LOCK "incl %0\n\t" /* ++sem->count */
204 "jle 2f\n"
205 "1:\n"
206 ".section .text.lock,\"ax\"\n"
207 "2:\tcall __up_wakeup\n\t"
208 "jmp 1b\n"
209 ".previous"
210 :"=m" (sem->count)
211 :"c" (sem)
212 :"memory");
213 }
215 #endif
216 #endif