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/*  $Id: smpprim.h,v 1.1 2005-12-20 11:32:11 jcastillo Exp $

 *  smpprim.h:  SMP locking primitives on the Sparc

 *

 *  God knows we won't be actually using this code for some time

 *  but I thought I'd write it since I knew how.

 *

 *  Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)

 */

#ifndef __SPARC_SMPPRIM_H

#define __SPARC_SMPPRIM_H

/* Test and set the unsigned byte at ADDR to 1.  Returns the previous

 * value.  On the Sparc we use the ldstub instruction since it is

 * atomic.

 */

extern inline volatile char test_and_set(void *addr)

{

        char state = 0;

        __asm__ __volatile__("ldstub [%0], %1         ! test_and_set\n\t"

                             "=r" (addr), "=r" (state) :

                             "0" (addr), "1" (state) : "memory");

        return state;

}

/* Initialize a spin-lock. */

extern inline volatile smp_initlock(void *spinlock)

{

        /* Unset the lock. */

        *((unsigned char *) spinlock) = 0;

        return;

}

/* This routine spins until it acquires the lock at ADDR. */

extern inline volatile smp_lock(void *addr)

{

        while(test_and_set(addr) == 0xff)

                ;

        /* We now have the lock */

        return;

}

/* This routine releases the lock at ADDR. */

extern inline volatile smp_unlock(void *addr)

{

        *((unsigned char *) addr) = 0;

}

#endif /* !(__SPARC_SMPPRIM_H) */