linux-kernel - [PATCH] powerpc: Implement atomic{,64}

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Date:	Sat, 11 Aug 2007 02:15:30 +0200
From:	Segher Boessenkool <segher@...nel.crashing.org>
To:	linuxppc-dev@...abs.org
Cc:	paulus@...ba.org, Segher Boessenkool <segher@...nel.crashing.org>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc: Implement atomic{,64}_{read,write}() without volatile

Instead, use asm() like all other atomic operations already do.

Also use inline functions instead of macros; this actually
improves code generation (some code becomes a little smaller,
probably because of improved alias information -- just a few
hundred bytes total on a default kernel build, nothing shocking).

Signed-off-by: Segher Boessenkool <segher@...nel.crashing.org>
---
 include/asm-powerpc/atomic.h |   34 ++++++++++++++++++++++++++++------
 1 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/include/asm-powerpc/atomic.h b/include/asm-powerpc/atomic.h
index c44810b..bc17506 100644
--- a/include/asm-powerpc/atomic.h
+++ b/include/asm-powerpc/atomic.h
@@ -5,7 +5,7 @@
  * PowerPC atomic operations
  */
 
-typedef struct { volatile int counter; } atomic_t;
+typedef struct { int counter; } atomic_t;
 
 #ifdef __KERNEL__
 #include <linux/compiler.h>
@@ -15,8 +15,19 @@ typedef struct { volatile int counter; } atomic_t;
 
 #define ATOMIC_INIT(i)		{ (i) }
 
-#define atomic_read(v)		((v)->counter)
-#define atomic_set(v,i)		(((v)->counter) = (i))
+static __inline__ int atomic_read(const atomic_t *v)
+{
+	int t;
+
+	__asm__ __volatile__("lwz%U1%X1 %0,%1" : "=r"(t) : "m"(v->counter));
+
+	return t;
+}
+
+static __inline__ void atomic_set(atomic_t *v, int i)
+{
+	__asm__ __volatile__("stw%U0%X0 %1,%0" : "=m"(v->counter) : "r"(i));
+}
 
 static __inline__ void atomic_add(int a, atomic_t *v)
 {
@@ -240,12 +251,23 @@ static __inline__ int atomic_dec_if_positive(atomic_t *v)
 
 #ifdef __powerpc64__
 
-typedef struct { volatile long counter; } atomic64_t;
+typedef struct { long counter; } atomic64_t;
 
 #define ATOMIC64_INIT(i)	{ (i) }
 
-#define atomic64_read(v)	((v)->counter)
-#define atomic64_set(v,i)	(((v)->counter) = (i))
+static __inline__ long atomic64_read(const atomic_t *v)
+{
+	long t;
+
+	__asm__ __volatile__("ld%U1%X1 %0,%1" : "=r"(t) : "m"(v->counter));
+
+	return t;
+}
+
+static __inline__ void atomic64_set(atomic_t *v, long i)
+{
+	__asm__ __volatile__("std%U0%X0 %1,%0" : "=m"(v->counter) : "r"(i));
+}
 
 static __inline__ void atomic64_add(long a, atomic64_t *v)
 {
-- 
1.5.2.1.144.gabc40-dirty

-
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