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 "" (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) */
55
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