Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 | #ifndef _I386_SEMAPHORE_H #define _I386_SEMAPHORE_H #include <linux/linkage.h> /* * SMP- and interrupt-safe semaphores.. * * (C) Copyright 1996 Linus Torvalds * * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in * the original code and to make semaphore waits * interruptible so that processes waiting on * semaphores can be killed. * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper * functions in asm/sempahore-helper.h while fixing a * potential and subtle race discovered by Ulrich Schmid * in down_interruptible(). Since I started to play here I * also implemented the `trylock' semaphore operation. * 1999-07-02 Artur Skawina <skawina@geocities.com> * Optimized "0(ecx)" -> "(ecx)" (the assembler does not * do this). Changed calling sequences from push/jmp to * traditional call/ret. * * If you would like to see an analysis of this implementation, please * ftp to gcom.com and download the file * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz. * */ #include <asm/system.h> #include <asm/atomic.h> #include <asm/spinlock.h> #include <linux/wait.h> struct semaphore { atomic_t count; int waking; wait_queue_head_t wait; #if WAITQUEUE_DEBUG long __magic; #endif }; #if WAITQUEUE_DEBUG # define __SEM_DEBUG_INIT(name) \ , (int)&(name).__magic #else # define __SEM_DEBUG_INIT(name) #endif #define __SEMAPHORE_INITIALIZER(name,count) \ { ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \ __SEM_DEBUG_INIT(name) } #define __MUTEX_INITIALIZER(name) \ __SEMAPHORE_INITIALIZER(name,1) #define __DECLARE_SEMAPHORE_GENERIC(name,count) \ struct semaphore name = __SEMAPHORE_INITIALIZER(name,count) #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1) #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0) extern inline void sema_init (struct semaphore *sem, int val) { /* * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val); * * i'd rather use the more flexible initialization above, but sadly * GCC 2.7.2.3 emits a bogus warning. EGCS doesnt. Oh well. */ atomic_set(&sem->count, val); sem->waking = 0; init_waitqueue_head(&sem->wait); #if WAITQUEUE_DEBUG sem->__magic = (int)&sem->__magic; #endif } static inline void init_MUTEX (struct semaphore *sem) { sema_init(sem, 1); } static inline void init_MUTEX_LOCKED (struct semaphore *sem) { sema_init(sem, 0); } asmlinkage void __down_failed(void /* special register calling convention */); asmlinkage int __down_failed_interruptible(void /* params in registers */); asmlinkage int __down_failed_trylock(void /* params in registers */); asmlinkage void __up_wakeup(void /* special register calling convention */); asmlinkage void __down(struct semaphore * sem); asmlinkage int __down_interruptible(struct semaphore * sem); asmlinkage int __down_trylock(struct semaphore * sem); asmlinkage void __up(struct semaphore * sem); extern spinlock_t semaphore_wake_lock; /* * This is ugly, but we want the default case to fall through. * "down_failed" is a special asm handler that calls the C * routine that actually waits. See arch/i386/lib/semaphore.S */ extern inline void down(struct semaphore * sem) { #if WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif __asm__ __volatile__( "# atomic down operation\n\t" #ifdef __SMP__ "lock ; " #endif "decl (%0)\n\t" /* --sem->count */ "js 2f\n" "1:\n" ".section .text.lock,\"ax\"\n" "2:\tcall __down_failed\n\t" "jmp 1b\n" ".previous" :/* no outputs */ :"c" (sem) :"memory"); } extern inline int down_interruptible(struct semaphore * sem) { int result; #if WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif __asm__ __volatile__( "# atomic interruptible down operation\n\t" #ifdef __SMP__ "lock ; " #endif "decl (%1)\n\t" /* --sem->count */ "js 2f\n\t" "xorl %0,%0\n" "1:\n" ".section .text.lock,\"ax\"\n" "2:\tcall __down_failed_interruptible\n\t" "jmp 1b\n" ".previous" :"=a" (result) :"c" (sem) :"memory"); return result; } extern inline int down_trylock(struct semaphore * sem) { int result; #if WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif __asm__ __volatile__( "# atomic interruptible down operation\n\t" #ifdef __SMP__ "lock ; " #endif "decl (%1)\n\t" /* --sem->count */ "js 2f\n\t" "xorl %0,%0\n" "1:\n" ".section .text.lock,\"ax\"\n" "2:\tcall __down_failed_trylock\n\t" "jmp 1b\n" ".previous" :"=a" (result) :"c" (sem) :"memory"); return result; } /* * Note! This is subtle. We jump to wake people up only if * the semaphore was negative (== somebody was waiting on it). * The default case (no contention) will result in NO * jumps for both down() and up(). */ extern inline void up(struct semaphore * sem) { #if WAITQUEUE_DEBUG CHECK_MAGIC(sem->__magic); #endif __asm__ __volatile__( "# atomic up operation\n\t" #ifdef __SMP__ "lock ; " #endif "incl (%0)\n\t" /* ++sem->count */ "jle 2f\n" "1:\n" ".section .text.lock,\"ax\"\n" "2:\tcall __up_wakeup\n\t" "jmp 1b\n" ".previous" :/* no outputs */ :"c" (sem) :"memory"); } #endif |