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#ifndef _I386_SEMAPHORE_H
#define _I386_SEMAPHORE_H
#include <linux/linkage.h>
#ifdef __KERNEL__
/*
* 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.
* Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
* Some hacks to ensure compatibility with recent
* GCC snapshots, to avoid stack corruption when compiling
* with -fomit-frame-pointer. It's not sure if this will
* be fixed in GCC, as our previous implementation was a
* bit dubious.
*
* 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 <linux/wait.h>
#include <linux/rwsem.h>
struct semaphore {
atomic_t count;
int sleepers;
wait_queue_head_t wait;
};
#define __SEMAPHORE_INITIALIZER(name, n) \
{ \
.count = ATOMIC_INIT(n), \
.sleepers = 0, \
.wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
}
#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)
static 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 doesn't. Oh well.
*/
atomic_set(&sem->count, val);
sem->sleepers = 0;
init_waitqueue_head(&sem->wait);
}
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);
}
fastcall void __down_failed(void /* special register calling convention */);
fastcall int __down_failed_interruptible(void /* params in registers */);
fastcall int __down_failed_trylock(void /* params in registers */);
fastcall void __up_wakeup(void /* special register calling convention */);
/*
* 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/kernel/semaphore.c
*/
static inline void down(struct semaphore * sem)
{
might_sleep();
__asm__ __volatile__(
"# atomic down operation\n\t"
LOCK_PREFIX "decl %0\n\t" /* --sem->count */
"js 2f\n"
"1:\n"
LOCK_SECTION_START("")
"2:\tlea %0,%%eax\n\t"
"call __down_failed\n\t"
"jmp 1b\n"
LOCK_SECTION_END
:"+m" (sem->count)
:
:"memory","ax");
}
/*
* Interruptible try to acquire a semaphore. If we obtained
* it, return zero. If we were interrupted, returns -EINTR
*/
static inline int down_interruptible(struct semaphore * sem)
{
int result;
might_sleep();
__asm__ __volatile__(
"# atomic interruptible down operation\n\t"
LOCK_PREFIX "decl %1\n\t" /* --sem->count */
"js 2f\n\t"
"xorl %0,%0\n"
"1:\n"
LOCK_SECTION_START("")
"2:\tlea %1,%%eax\n\t"
"call __down_failed_interruptible\n\t"
"jmp 1b\n"
LOCK_SECTION_END
:"=a" (result), "+m" (sem->count)
:
:"memory");
return result;
}
/*
* Non-blockingly attempt to down() a semaphore.
* Returns zero if we acquired it
*/
static inline int down_trylock(struct semaphore * sem)
{
int result;
__asm__ __volatile__(
"# atomic interruptible down operation\n\t"
LOCK_PREFIX "decl %1\n\t" /* --sem->count */
"js 2f\n\t"
"xorl %0,%0\n"
"1:\n"
LOCK_SECTION_START("")
"2:\tlea %1,%%eax\n\t"
"call __down_failed_trylock\n\t"
"jmp 1b\n"
LOCK_SECTION_END
:"=a" (result), "+m" (sem->count)
:
:"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().
*/
static inline void up(struct semaphore * sem)
{
__asm__ __volatile__(
"# atomic up operation\n\t"
LOCK_PREFIX "incl %0\n\t" /* ++sem->count */
"jle 2f\n"
"1:\n"
LOCK_SECTION_START("")
"2:\tlea %0,%%eax\n\t"
"call __up_wakeup\n\t"
"jmp 1b\n"
LOCK_SECTION_END
".subsection 0\n"
:"+m" (sem->count)
:
:"memory","ax");
}
#endif
#endif
|
