include/asm-i386/semaphore.h

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 1 #ifndef _I386_SEMAPHORE_H
 2 #define _I386_SEMAPHORE_H
 3
 4 #include <linux/linkage.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/system.h>
 32 #include <asm/atomic.h>
 33 #include <linux/spinlock.h>
 34 #include <linux/wait.h>
 35
 36 struct semaphore {
 37  atomic_t count;
 38 int sleepers;
 39  wait_queue_head_t wait;
 40 #if WAITQUEUE_DEBUG
 41 long __magic;
 42 #endif
 43 };
 44
 45 #if WAITQUEUE_DEBUG
 46 # define __SEM_DEBUG_INIT(name) \
 47  , (int)&(name).__magic
 48 #else
 49 # define __SEM_DEBUG_INIT(name)
 50 #endif
 51
 52 #define __SEMAPHORE_INITIALIZER(name,count) \
 53 { ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
 54  __SEM_DEBUG_INIT(name) }
 55
 56 #define __MUTEX_INITIALIZER(name) \
 57  __SEMAPHORE_INITIALIZER(name,1)
 58
 59 #define __DECLARE_SEMAPHORE_GENERIC(name,count) \
 60  struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
 61
 62 #define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
 63 #define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
 64
 65 extern inlinevoidsema_init(struct semaphore *sem,int val)
 66 {
 67 /*
 68  * *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
 69  *
 70  * i'd rather use the more flexible initialization above, but sadly
 71  * GCC 2.7.2.3 emits a bogus warning. EGCS doesnt. Oh well.
 72  */
 73 atomic_set(&sem->count, val);
 74  sem->sleepers =0;
 75 init_waitqueue_head(&sem->wait);
 76 #if WAITQUEUE_DEBUG
 77  sem->__magic = (int)&sem->__magic;
 78 #endif
 79 }
 80
 81 staticinlinevoidinit_MUTEX(struct semaphore *sem)
 82 {
 83 sema_init(sem,1);
 84 }
 85
 86 staticinlinevoidinit_MUTEX_LOCKED(struct semaphore *sem)
 87 {
 88 sema_init(sem,0);
 89 }
 90
 91 asmlinkage void__down_failed(void/* special register calling convention */);
 92 asmlinkage int__down_failed_interruptible(void/* params in registers */);
 93 asmlinkage int__down_failed_trylock(void/* params in registers */);
 94 asmlinkage void__up_wakeup(void/* special register calling convention */);
 95
 96 asmlinkage void__down(struct semaphore * sem);
 97 asmlinkage int__down_interruptible(struct semaphore * sem);
 98 asmlinkage int__down_trylock(struct semaphore * sem);
 99 asmlinkage void__up(struct semaphore * sem);
 100
 101 extern spinlock_t semaphore_wake_lock;
 102
 103 /*
 104  * This is ugly, but we want the default case to fall through.
 105  * "down_failed" is a special asm handler that calls the C
 106  * routine that actually waits. See arch/i386/lib/semaphore.S
 107  */
 108 extern inlinevoiddown(struct semaphore * sem)
 109 {
 110 #if WAITQUEUE_DEBUG
 111 CHECK_MAGIC(sem->__magic);
 112 #endif
 113
 114  __asm__ __volatile__(
 115 "# atomic down operation\n\t"
 116 #ifdef __SMP__
 117 "lock ; "
 118 #endif
 119 "decl (%0)\n\t"/* --sem->count */
 120 "js 2f\n"
 121 "1:\n"
 122 ".section .text.lock,\"ax\"\n"
 123 "2:\tcall __down_failed\n\t"
 124 "jmp 1b\n"
 125 ".previous"
 126 :/* no outputs */
 127 :"c"(sem)
 128 :"memory");
 129 }
 130
 131 extern inlineintdown_interruptible(struct semaphore * sem)
 132 {
 133 int result;
 134
 135 #if WAITQUEUE_DEBUG
 136 CHECK_MAGIC(sem->__magic);
 137 #endif
 138
 139  __asm__ __volatile__(
 140 "# atomic interruptible down operation\n\t"
 141 #ifdef __SMP__
 142 "lock ; "
 143 #endif
 144 "decl (%1)\n\t"/* --sem->count */
 145 "js 2f\n\t"
 146 "xorl %0,%0\n"
 147 "1:\n"
 148 ".section .text.lock,\"ax\"\n"
 149 "2:\tcall __down_failed_interruptible\n\t"
 150 "jmp 1b\n"
 151 ".previous"
 152 :"=a"(result)
 153 :"c"(sem)
 154 :"memory");
 155 return result;
 156 }
 157
 158 extern inlineintdown_trylock(struct semaphore * sem)
 159 {
 160 int result;
 161
 162 #if WAITQUEUE_DEBUG
 163 CHECK_MAGIC(sem->__magic);
 164 #endif
 165
 166  __asm__ __volatile__(
 167 "# atomic interruptible down operation\n\t"
 168 #ifdef __SMP__
 169 "lock ; "
 170 #endif
 171 "decl (%1)\n\t"/* --sem->count */
 172 "js 2f\n\t"
 173 "xorl %0,%0\n"
 174 "1:\n"
 175 ".section .text.lock,\"ax\"\n"
 176 "2:\tcall __down_failed_trylock\n\t"
 177 "jmp 1b\n"
 178 ".previous"
 179 :"=a"(result)
 180 :"c"(sem)
 181 :"memory");
 182 return result;
 183 }
 184
 185 /*
 186  * Note! This is subtle. We jump to wake people up only if
 187  * the semaphore was negative (== somebody was waiting on it).
 188  * The default case (no contention) will result in NO
 189  * jumps for both down() and up().
 190  */
 191 extern inlinevoidup(struct semaphore * sem)
 192 {
 193 #if WAITQUEUE_DEBUG
 194 CHECK_MAGIC(sem->__magic);
 195 #endif
 196  __asm__ __volatile__(
 197 "# atomic up operation\n\t"
 198 #ifdef __SMP__
 199 "lock ; "
 200 #endif
 201 "incl (%0)\n\t"/* ++sem->count */
 202 "jle 2f\n"
 203 "1:\n"
 204 ".section .text.lock,\"ax\"\n"
 205 "2:\tcall __up_wakeup\n\t"
 206 "jmp 1b\n"
 207 ".previous"
 208 :/* no outputs */
 209 :"c"(sem)
 210 :"memory");
 211 }
 212
 213 #endif