blob: 8ddcb33068e00f6d2bc25a4d739d002877e1cd0f (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
|
/* $OpenBSD: _atomic_lock.c,v 1.2 1998/12/18 05:59:17 d Exp $ */
/*
* Atomic lock for i386
*/
#include "spinlock.h"
register_t
_atomic_lock(volatile register_t *lock)
{
register_t old;
/*
* Use the eXCHanGe instruction to swap the lock value with
* a local variable containg '1' (the locked state).
*/
old = 1;
__asm__("xchg %0, %1"
: "=r" (old), "=m" (*lock) : "0"(old), "1" (*lock) );
/*
* So now there is a 1 in *lock and 'old' contains what
* used to be in the lock. We return 0 if the lock was acquired,
* (ie its old value was 0) or 1 otherwise.
*/
return old;
}
int
_atomic_is_locked(volatile register_t *lock)
{
return *lock;
}
|
