include/asm-sparc/smpprim.h

   1 /*  $Id: smpprim.h,v 1.5 1996/08/29 09:48:49 davem Exp $
   2  *  smpprim.h:  SMP locking primitives on the Sparc
   3  *
   4  *  God knows we won't be actually using this code for some time
   5  *  but I thought I'd write it since I knew how.
   6  *
   7  *  Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
   8  */
   9
  10 #ifndef __SPARC_SMPPRIM_H
  11 #define __SPARC_SMPPRIM_H
  12
  13 /* Test and set the unsigned byte at ADDR to 1.  Returns the previous
  14  * value.  On the Sparc we use the ldstub instruction since it is
  15  * atomic.
  16  */
  17
  18 extern __inline__ __volatile__ char test_and_set(void *addr)
  19 {
  20         char state = 0;
  21
  22         __asm__ __volatile__("ldstub [%0], %1         ! test_and_set\n\t"
  23                              "=r" (addr), "=r" (state) :
  24                              "0" (addr), "1" (state) : "memory");
  25
  26         return state;
  27 }
  28
  29 /* Initialize a spin-lock. */
  30 extern __inline__ __volatile__ smp_initlock(void *spinlock)
  31 {
  32         /* Unset the lock. */
  33         *((unsigned char *) spinlock) = 0;
  34
  35         return;
  36 }
  37
  38 /* This routine spins until it acquires the lock at ADDR. */
  39 extern __inline__ __volatile__ smp_lock(void *addr)
  40 {
  41         while(test_and_set(addr) == 0xff)
  42                 ;
  43
  44         /* We now have the lock */
  45         return;
  46 }
  47
  48 /* This routine releases the lock at ADDR. */
  49 extern __inline__ __volatile__ smp_unlock(void *addr)
  50 {
  51         *((unsigned char *) addr) = 0;
  52 }
  53
  54 #endif /* !(__SPARC_SMPPRIM_H) */