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#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.
*
* 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
}
#define sema_init(sem,val) \
do { \
struct semaphore *__sem = (sem); \
printk("sema_init called at %s, %d for semaphore 0x%08lx\n", \
__FILE__, __LINE__, (unsigned long) __sem); \
__sema_init(__sem, (val)); \
while(1);
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(%0)\n\t"
"js 2f\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __down_failed\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 0(%1)\n\t"
"js 2f\n\t"
"xorl %0,%0\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __down_failed_interruptible\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 0(%1)\n\t"
"js 2f\n\t"
"xorl %0,%0\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __down_failed_trylock\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(%0)\n\t"
"jle 2f\n"
"1:\n"
".section .text.lock,\"ax\"\n"
"2:\tpushl $1b\n\t"
"jmp __up_wakeup\n"
".previous"
:/* no outputs */
:"c" (sem)
:"memory");
}
#endif
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