blob: e3eb2aab29054700afd8c120d1ba4ec136893086 (
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
34
35
36
37
38
39
40
41
42
43
|
/* $OpenBSD: _atomic_lock.c,v 1.3 2002/07/10 20:30:13 jsyn Exp $ */
/*
* Atomic lock for powerpc
*/
#include "spinlock.h"
int
_atomic_lock(volatile _spinlock_lock_t *lock)
{
_spinlock_lock_t old;
__asm__("1: lwarx %0,0,%1 \n"
" stwcx. %2,0,%1 \n"
" bne- 1b \n"
: "=r" (old), "=r" (lock)
: "r" (_SPINLOCK_LOCKED), "1" (lock)
);
return (old != _SPINLOCK_UNLOCKED);
/*
* Dale <rahnds@openbsd.org> says:
* Side note. to prevent two processes from accessing
* the same address with the lwarx in one instrution
* and the stwcx in another process, the current powerpc
* kernel uses a stwcx instruction without the corresponding
* lwarx which causes any reservation of a process
* to be removed. if a context switch occurs
* between the two accesses the store will not occur
* and the condition code will cause it to loop. If on
* a dual processor machine, the reserve will cause
* appropriate bus cycle accesses to notify other
* processors.
*/
}
int
_atomic_is_locked(volatile _spinlock_lock_t *lock)
{
return (*lock != _SPINLOCK_UNLOCKED);
}
|
