1/*  $Id: smpprim.h,v 1.1.1.1 2007/08/03 18:53:36 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
18static 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. */
30static 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. */
39static 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. */
49static inline __volatile__ smp_unlock(void *addr)
50{
51	*((unsigned char *) addr) = 0;
52}
53
54#endif /* !(__SPARC_SMPPRIM_H) */
55