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smpprim.h

/*
 *  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.
 */

static 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. */
static inline __volatile__ smp_initlock(void *spinlock)
{
      /* Unset the lock. */
      *((unsigned char *) spinlock) = 0;

      return;
}

/* This routine spins until it acquires the lock at ADDR. */
static 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. */
static inline __volatile__ smp_unlock(void *addr)
{
      *((unsigned char *) addr) = 0;
}

#endif /* !(__SPARC_SMPPRIM_H) */

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