As Segher pointed out, inline asm is better than the volatile casting all over
the place. From the PowerPC patch description:
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).
My config with march=k8 and gcc (GCC) 4.1.2 (Gentoo 4.1.2):
text data bss dec hex filename
4002473 385936 474440 4862849 4a3381 atomic_normal/vmlinux
4002587 385936 474440 4862963 4a33f3 atomic_inlineasm/vmlinux
4003911 385936 474440 4864287 4a391f atomic_volatile/vmlinux
4003959 385936 474440 4864335 4a394f atomic_volatile_inline/vmlinux
Signed-off-by: Sebastian Siewior <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Chris Snook <[email protected]>
--- a/include/asm-x86_64/atomic.h
+++ b/include/asm-x86_64/atomic.h
@@ -32,7 +32,16 @@ typedef struct { int counter; } atomic_t
*
* Atomically reads the value of @v.
*/
-#define atomic_read(v) ((v)->counter)
+static inline int atomic_read(const atomic_t *v)
+{
+ int t;
+
+ asm volatile(
+ "movl %1, %0"
+ : "=r"(t)
+ : "m"(v->counter));
+ return t;
+}
/**
* atomic_set - set atomic variable
@@ -41,7 +50,13 @@ typedef struct { int counter; } atomic_t
*
* Atomically sets the value of @v to @i.
*/
-#define atomic_set(v,i) (((v)->counter) = (i))
+static inline void atomic_set(atomic_t *v, int i)
+{
+ asm volatile(
+ "movl %1, %0"
+ : "=m"(v->counter)
+ : "ir"(i));
+}
/**
* atomic_add - add integer to atomic variable
@@ -206,7 +221,7 @@ static __inline__ int atomic_sub_return(
/* An 64bit atomic type */
-typedef struct { volatile long counter; } atomic64_t;
+typedef struct { long counter; } atomic64_t;
#define ATOMIC64_INIT(i) { (i) }
@@ -217,7 +232,16 @@ typedef struct { volatile long counter;
* Atomically reads the value of @v.
* Doesn't imply a read memory barrier.
*/
-#define atomic64_read(v) ((v)->counter)
+static inline long atomic64_read(const atomic64_t *v)
+{
+ long t;
+
+ asm volatile(
+ "movq %1, %0"
+ : "=r"(t)
+ : "m"(v->counter));
+ return t;
+}
/**
* atomic64_set - set atomic64 variable
@@ -226,7 +250,13 @@ typedef struct { volatile long counter;
*
* Atomically sets the value of @v to @i.
*/
-#define atomic64_set(v,i) (((v)->counter) = (i))
+static inline void atomic64_set(atomic64_t *v, long i)
+{
+ asm volatile(
+ "movq %1, %0"
+ : "=m"(v->counter)
+ : "ir"(i));
+}
/**
* atomic64_add - add integer to atomic64 variable
--
-
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