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#ifndef _I386_SEMAPHORE_H

#define _I386_SEMAPHORE_H

#include <linux/linkage.h>

#include <asm/system.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.

 *

 * 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.

 *

 */

struct semaphore {

        int count;

        int waking;

        int lock ;                      /* to make waking testing atomic */

        struct wait_queue * wait;

};

#define MUTEX ((struct semaphore) { 1, 0, 0, NULL })

#define MUTEX_LOCKED ((struct semaphore) { 0, 0, 0, NULL })

asmlinkage void down_failed(void /* special register calling convention */);

asmlinkage void up_wakeup(void /* special register calling convention */);

extern void __down(struct semaphore * sem);

extern 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/i386/lib/semaphore.S

 */

extern inline void down(struct semaphore * sem)

{

        __asm__ __volatile__(

                "# atomic down operation\n\t"

                "movl $1f,%%eax\n\t"

#ifdef __SMP__

                "lock ; "

#endif

                "decl 0(%0)\n\t"

                "js " SYMBOL_NAME_STR(down_failed) "\n"

                "1:\n"

                :/* no outputs */

                :"c" (sem)

                :"ax","dx","memory");

}

/*

 * Primitives to spin on a lock.  Needed only for SMP version.

 */

extern inline void get_buzz_lock(int *lock_ptr)

{

#ifdef __SMP__

        while (xchg(lock_ptr,1) != 0) ;

#endif

} /* get_buzz_lock */

extern inline void give_buzz_lock(int *lock_ptr)

{

#ifdef __SMP__

        *lock_ptr = 0 ;

#endif

} /* give_buzz_lock */

asmlinkage int down_failed_interruptible(void);  /* params in registers */

/*

 * This version waits in interruptible state so that the waiting

 * process can be killed.  The down_failed_interruptible routine

 * returns negative for signalled and zero for semaphore acquired.

 */

extern inline int down_interruptible(struct semaphore * sem)

{

        int     ret ;

        __asm__ __volatile__(

                "# atomic interruptible down operation\n\t"

                "movl $2f,%%eax\n\t"

#ifdef __SMP__

                "lock ; "

#endif

                "decl 0(%1)\n\t"

                "js " SYMBOL_NAME_STR(down_failed_interruptible) "\n\t"

                "xorl %%eax,%%eax\n"

                "2:\n"

                :"=a" (ret)

                :"c" (sem)

                :"ax","dx","memory");

        return(ret) ;

}

/*

 * 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)

{

        __asm__ __volatile__(

                "# atomic up operation\n\t"

                "movl $1f,%%eax\n\t"

#ifdef __SMP__

                "lock ; "

#endif

                "incl 0(%0)\n\t"

                "jle " SYMBOL_NAME_STR(up_wakeup)

                "\n1:"

                :/* no outputs */

                :"c" (sem)

                :"ax", "dx", "memory");

}

#endif