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[S390] atomic: implement atomic64_dec_if_positive

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Implement atomic64_dec_if_positive and add missing system.h header
include.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2010-05-26 23:26:18 +02:00 committed by Martin Schwidefsky
parent 1ef6acf597
commit 2ddb3ec414
1 changed files with 19 additions and 0 deletions
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19
arch/s390/include/asm/atomic.h
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@ -15,6 +15,7 @@
#include <linux/compiler.h>
#include <linux/types.h>
#include <asm/system.h>
#define ATOMIC_INIT(i) { (i) }
@ -274,6 +275,7 @@ static inline void atomic64_clear_mask(unsigned long long mask, atomic64_t *v)
static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)
{
long long c, old;
c = atomic64_read(v);
for (;;) {
if (unlikely(c == u))
@ -286,6 +288,23 @@ static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)
return c != u;
}
static inline long long atomic64_dec_if_positive(atomic64_t *v)
{
long long c, old, dec;
c = atomic64_read(v);
for (;;) {
dec = c - 1;
if (unlikely(dec < 0))
break;
old = atomic64_cmpxchg((v), c, dec);
if (likely(old == c))
break;
c = old;
}
return dec;
}
#define atomic64_add(_i, _v) atomic64_add_return(_i, _v)
#define atomic64_add_negative(_i, _v) (atomic64_add_return(_i, _v) < 0)
#define atomic64_inc(_v) atomic64_add_return(1, _v)