Subversion Repositories or1k

#ifndef _X86_64_SEMAPHORE_H

#define _X86_64_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 <asm/rwlock.h>

#include <linux/wait.h>

#include <linux/rwsem.h>

#include <linux/stringify.h>

struct semaphore {

        atomic_t count;

        int sleepers;

        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)

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 doesnt. Oh well.

 */

        atomic_set(&sem->count, val);

        sem->sleepers = 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);

/*

 * 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/x86_64/kernel/semaphore.c

 */

static inline void down(struct semaphore * sem)

{

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        __asm__ __volatile__(

                "# atomic down operation\n\t"

                LOCK "decl %0\n\t"     /* --sem->count */

                "js 2f\n"

                "1:\n"

                LOCK_SECTION_START("")

                "2:\tcall __down_failed\n\t"

                "jmp 1b\n"

                LOCK_SECTION_END

                :"=m" (sem->count)

                :"D" (sem)

                :"memory");

}

/*

 * 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;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        __asm__ __volatile__(

                "# atomic interruptible down operation\n\t"

                LOCK "decl %1\n\t"     /* --sem->count */

                "js 2f\n\t"

                "xorl %0,%0\n"

                "1:\n"

                LOCK_SECTION_START("")

                "2:\tcall __down_failed_interruptible\n\t"

                "jmp 1b\n"

                LOCK_SECTION_END

                :"=a" (result), "=m" (sem->count)

                :"D" (sem)

                :"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;

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        __asm__ __volatile__(

                "# atomic interruptible down operation\n\t"

                LOCK "decl %1\n\t"     /* --sem->count */

                "js 2f\n\t"

                "xorl %0,%0\n"

                "1:\n"

                LOCK_SECTION_START("")

                "2:\tcall __down_failed_trylock\n\t"

                "jmp 1b\n"

                LOCK_SECTION_END

                :"=a" (result), "=m" (sem->count)

                :"D" (sem)

                :"memory","cc");

        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)

{

#if WAITQUEUE_DEBUG

        CHECK_MAGIC(sem->__magic);

#endif

        __asm__ __volatile__(

                "# atomic up operation\n\t"

                LOCK "incl %0\n\t"     /* ++sem->count */

                "jle 2f\n"

                "1:\n"

                LOCK_SECTION_START("")

                "2:\tcall __up_wakeup\n\t"

                "jmp 1b\n"

                LOCK_SECTION_END

                :"=m" (sem->count)

                :"D" (sem)

                :"memory");

}

static inline int sem_getcount(struct semaphore *sem)

{

        return atomic_read(&sem->count);

}

#endif /* __KERNEL__ */

#endif