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authorNick Piggin <npiggin@suse.de>2006-02-20 10:41:40 +0100
committerPaul Mackerras <paulus@samba.org>2006-02-24 14:06:02 +1100
commitf055affb89f587a03f3411c3fd49ef31295c3d48 (patch)
tree1c40a29191eba8267390fe397f8108ffa8d9ddb5 /include/asm-powerpc/atomic.h
parent4f629d7db32decbadaab2abfa4d021fee94990ef (diff)
downloadlwn-f055affb89f587a03f3411c3fd49ef31295c3d48.tar.gz
lwn-f055affb89f587a03f3411c3fd49ef31295c3d48.zip
[PATCH] powerpc: native atomic_add_unless
Do atomic_add_unless natively instead of using cmpxchg. Improved register allocation idea from Joel Schopp. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'include/asm-powerpc/atomic.h')
-rw-r--r--include/asm-powerpc/atomic.h38
1 files changed, 24 insertions, 14 deletions
diff --git a/include/asm-powerpc/atomic.h b/include/asm-powerpc/atomic.h
index 147a38dcc766..bb3c0ab7e667 100644
--- a/include/asm-powerpc/atomic.h
+++ b/include/asm-powerpc/atomic.h
@@ -8,6 +8,7 @@
typedef struct { volatile int counter; } atomic_t;
#ifdef __KERNEL__
+#include <linux/compiler.h>
#include <asm/synch.h>
#include <asm/asm-compat.h>
@@ -176,20 +177,29 @@ static __inline__ int atomic_dec_return(atomic_t *v)
* Atomically adds @a to @v, so long as it was not @u.
* Returns non-zero if @v was not @u, and zero otherwise.
*/
-#define atomic_add_unless(v, a, u) \
-({ \
- int c, old; \
- c = atomic_read(v); \
- for (;;) { \
- if (unlikely(c == (u))) \
- break; \
- old = atomic_cmpxchg((v), c, c + (a)); \
- if (likely(old == c)) \
- break; \
- c = old; \
- } \
- c != (u); \
-})
+static __inline__ int atomic_add_unless(atomic_t *v, int a, int u)
+{
+ int t;
+
+ __asm__ __volatile__ (
+ LWSYNC_ON_SMP
+"1: lwarx %0,0,%1 # atomic_add_unless\n\
+ cmpw 0,%0,%3 \n\
+ beq- 2f \n\
+ add %0,%2,%0 \n"
+ PPC405_ERR77(0,%2)
+" stwcx. %0,0,%1 \n\
+ bne- 1b \n"
+ ISYNC_ON_SMP
+" subf %0,%2,%0 \n\
+2:"
+ : "=&r" (t)
+ : "r" (&v->counter), "r" (a), "r" (u)
+ : "cc", "memory");
+
+ return t != u;
+}
+
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)
#define atomic_sub_and_test(a, v) (atomic_sub_return((a), (v)) == 0)