1#ifndef _X86_64_SEMAPHORE_H 2#define _X86_64_SEMAPHORE_H 3 4#include <linux/linkage.h> 5 6#ifdef __KERNEL__ 7 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 */ 38 39#include <asm/system.h> 40#include <asm/atomic.h> 41#include <asm/rwlock.h> 42#include <linux/wait.h> 43#include <linux/rwsem.h> 44#include <linux/stringify.h> 45 46struct semaphore { 47 atomic_t count; 48 int sleepers; 49 wait_queue_head_t wait; 50#if WAITQUEUE_DEBUG 51 long __magic; 52#endif 53}; 54 55#if WAITQUEUE_DEBUG 56# define __SEM_DEBUG_INIT(name) \ 57 , (int)&(name).__magic 58#else 59# define __SEM_DEBUG_INIT(name) 60#endif 61 62#define __SEMAPHORE_INITIALIZER(name,count) \ 63{ ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ 64 __SEM_DEBUG_INIT(name) } 65 66#define __MUTEX_INITIALIZER(name) \ 67 __SEMAPHORE_INITIALIZER(name,1) 68 69#define __DECLARE_SEMAPHORE_GENERIC(name,count) \ 70 struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) 71 72#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) 73#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) 74 75static inline void sema_init (struct semaphore *sem, int val) 76{ 77/* 78 * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); 79 * 80 * i'd rather use the more flexible initialization above, but sadly 81 * GCC 2.7.2.3 emits a bogus warning. EGCS doesnt. Oh well. 82 */ 83 atomic_set(&sem->count, val); 84 sem->sleepers = 0; 85 init_waitqueue_head(&sem->wait); 86#if WAITQUEUE_DEBUG 87 sem->__magic = (int)&sem->__magic; 88#endif 89} 90 91static inline void init_MUTEX (struct semaphore *sem) 92{ 93 sema_init(sem, 1); 94} 95 96static inline void init_MUTEX_LOCKED (struct semaphore *sem) 97{ 98 sema_init(sem, 0); 99} 100 101asmlinkage void __down_failed(void /* special register calling convention */); 102asmlinkage int __down_failed_interruptible(void /* params in registers */); 103asmlinkage int __down_failed_trylock(void /* params in registers */); 104asmlinkage void __up_wakeup(void /* special register calling convention */); 105 106asmlinkage void __down(struct semaphore * sem); 107asmlinkage int __down_interruptible(struct semaphore * sem); 108asmlinkage int __down_trylock(struct semaphore * sem); 109asmlinkage void __up(struct semaphore * sem); 110 111/* 112 * This is ugly, but we want the default case to fall through. 113 * "__down_failed" is a special asm handler that calls the C 114 * routine that actually waits. See arch/x86_64/kernel/semaphore.c 115 */ 116static inline void down(struct semaphore * sem) 117{ 118#if WAITQUEUE_DEBUG 119 CHECK_MAGIC(sem->__magic); 120#endif 121 122 __asm__ __volatile__( 123 "# atomic down operation\n\t" 124 LOCK "decl %0\n\t" /* --sem->count */ 125 "js 2f\n" 126 "1:\n" 127 ".subsection 1\n" \ 128 ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \ 129 "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \ 130 ".endif\n" \ 131 "2:\tcall __down_failed\n\t" 132 "jmp 1b\n" 133 ".subsection 0" 134 :"=m" (sem->count) 135 :"D" (sem) 136 :"memory"); 137} 138 139/* 140 * Interruptible try to acquire a semaphore. If we obtained 141 * it, return zero. If we were interrupted, returns -EINTR 142 */ 143static inline int down_interruptible(struct semaphore * sem) 144{ 145 int result; 146 147#if WAITQUEUE_DEBUG 148 CHECK_MAGIC(sem->__magic); 149#endif 150 151 __asm__ __volatile__( 152 "# atomic interruptible down operation\n\t" 153 LOCK "decl %1\n\t" /* --sem->count */ 154 "js 2f\n\t" 155 "xorl %0,%0\n" 156 "1:\n" 157 ".subsection 1\n" \ 158 ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \ 159 "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \ 160 ".endif\n" \ 161 "2:\tcall __down_failed_interruptible\n\t" 162 "jmp 1b\n" 163 ".subsection 0" 164 :"=a" (result), "=m" (sem->count) 165 :"D" (sem) 166 :"memory"); 167 return result; 168} 169 170/* 171 * Non-blockingly attempt to down() a semaphore. 172 * Returns zero if we acquired it 173 */ 174static inline int down_trylock(struct semaphore * sem) 175{ 176 int result; 177 178#if WAITQUEUE_DEBUG 179 CHECK_MAGIC(sem->__magic); 180#endif 181 182 __asm__ __volatile__( 183 "# atomic interruptible down operation\n\t" 184 LOCK "decl %1\n\t" /* --sem->count */ 185 "js 2f\n\t" 186 "xorl %0,%0\n" 187 "1:\n" 188 ".subsection 1\n" \ 189 ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \ 190 "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \ 191 ".endif\n" \ 192 "2:\tcall __down_failed_trylock\n\t" 193 "jmp 1b\n" 194 ".subsection 0" 195 :"=a" (result), "=m" (sem->count) 196 :"D" (sem) 197 :"memory","cc"); 198 return result; 199} 200 201/* 202 * Note! This is subtle. We jump to wake people up only if 203 * the semaphore was negative (== somebody was waiting on it). 204 * The default case (no contention) will result in NO 205 * jumps for both down() and up(). 206 */ 207static inline void up(struct semaphore * sem) 208{ 209#if WAITQUEUE_DEBUG 210 CHECK_MAGIC(sem->__magic); 211#endif 212 __asm__ __volatile__( 213 "# atomic up operation\n\t" 214 LOCK "incl %0\n\t" /* ++sem->count */ 215 "jle 2f\n" 216 "1:\n" 217 ".subsection 1\n" \ 218 ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \ 219 "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \ 220 ".endif\n" \ 221 "2:\tcall __up_wakeup\n\t" 222 "jmp 1b\n" 223 ".subsection 0" 224 :"=m" (sem->count) 225 :"D" (sem) 226 :"memory"); 227} 228 229static inline int sem_getcount(struct semaphore *sem) 230{ 231 return atomic_read(&sem->count); 232} 233 234#endif /* __KERNEL__ */ 235#endif 236