[PATCH 5/5] x86,atomic: Use atomic_try_cmpxchg

[Peter Zijlstra <peterz@infradead.org>]

[-- Attachment #1: peterz-x86-atomic-try_cmpxchg.patch --]
[-- Type: text/plain, Size: 3259 bytes --]

   text	   data	    bss	    dec	    hex	filename
10665111        4530096  843776 16038983         f4bc47 defconfig-build/vmlinux.3
10655703        4530096  843776 16029575         f49787 defconfig-build/vmlinux.4

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/include/asm/atomic.h      |   27 ++++++++----------------
 arch/x86/include/asm/atomic64_64.h |   40 ++++++++++++-------------------------
 2 files changed, 22 insertions(+), 45 deletions(-)

--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -207,16 +207,12 @@ static inline void atomic_##op(int i, at
 }
 
 #define ATOMIC_FETCH_OP(op, c_op)					\
-static inline int atomic_fetch_##op(int i, atomic_t *v)		\
+static inline int atomic_fetch_##op(int i, atomic_t *v)			\
 {									\
-	int old, val = atomic_read(v);					\
-	for (;;) {							\
-		old = atomic_cmpxchg(v, val, val c_op i);		\
-		if (old == val)						\
-			break;						\
-		val = old;						\
-	}								\
-	return old;							\
+	int val = atomic_read(v);					\
+	do {								\
+	} while (!atomic_try_cmpxchg(v, &val, val c_op i));		\
+	return val;							\
 }
 
 #define ATOMIC_OPS(op, c_op)						\
@@ -242,16 +238,11 @@ ATOMIC_OPS(xor, ^)
  */
 static __always_inline int __atomic_add_unless(atomic_t *v, int a, int u)
 {
-	int c, old;
-	c = atomic_read(v);
-	for (;;) {
-		if (unlikely(c == (u)))
+	int c = atomic_read(v);
+	do {
+		if (unlikely(c == u))
 			break;
-		old = atomic_cmpxchg((v), c, c + (a));
-		if (likely(old == c))
-			break;
-		c = old;
-	}
+	} while (!atomic_try_cmpxchg(v, &c, c + a));
 	return c;
 }
 
--- a/arch/x86/include/asm/atomic64_64.h
+++ b/arch/x86/include/asm/atomic64_64.h
@@ -198,17 +198,12 @@ static inline long atomic64_xchg(atomic6
  */
 static inline bool atomic64_add_unless(atomic64_t *v, long a, long u)
 {
-	long c, old;
-	c = atomic64_read(v);
-	for (;;) {
-		if (unlikely(c == (u)))
-			break;
-		old = atomic64_cmpxchg((v), c, c + (a));
-		if (likely(old == c))
-			break;
-		c = old;
-	}
-	return c != (u);
+	long c = atomic64_read(v);
+	do {
+		if (unlikely(c == u))
+			return false;
+	} while (!atomic64_try_cmpxchg(v, &c, c + a));
+	return true;
 }
 
 #define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
@@ -222,17 +217,12 @@ static inline bool atomic64_add_unless(a
  */
 static inline long atomic64_dec_if_positive(atomic64_t *v)
 {
-	long c, old, dec;
-	c = atomic64_read(v);
-	for (;;) {
+	long dec, c = atomic64_read(v);
+	do {
 		dec = c - 1;
 		if (unlikely(dec < 0))
 			break;
-		old = atomic64_cmpxchg((v), c, dec);
-		if (likely(old == c))
-			break;
-		c = old;
-	}
+	} while (!atomic64_try_cmpxchg(v, &c, dec));
 	return dec;
 }
 
@@ -248,14 +238,10 @@ static inline void atomic64_##op(long i,
 #define ATOMIC64_FETCH_OP(op, c_op)					\
 static inline long atomic64_fetch_##op(long i, atomic64_t *v)		\
 {									\
-	long old, val = atomic64_read(v);				\
-	for (;;) {							\
-		old = atomic64_cmpxchg(v, val, val c_op i);		\
-		if (old == val)						\
-			break;						\
-		val = old;						\
-	}								\
-	return old;							\
+	long val = atomic64_read(v);					\
+	do {								\
+	} while (!atomic64_try_cmpxchg(v, &val, val c_op i));		\
+	return val;							\
 }
 
 #define ATOMIC64_OPS(op, c_op)						\