text: /*  $Id: smpprim.h,v 1.1.1.1 2007-05-25 06:50:13 bruce 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.
   */
  
  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) */
  