[PATCH] atomic.h : standardizing atomic primitives

Peter Zijlstra
2007-01-31T15:28:50Z

atomic.h : standardizing atomic primitives

It mainly adds support for missing 64 bits cmpxchg and 64 bits atomic add
unless. Therefore, principally 64 bits architectures are targeted by these
patches. It also adds the complete list of atomic operations on the atomic_long
type.

build tested on:

arm-pxa255-idp_defconfig-xbuild
i386-defconfig-xbuild
ia64-defconfig-xbuild
mips-ip32_defconfig-xbuild
mips-yosemite_defconfig-xbuild
parisc-a500_defconfig-xbuild -- needs parisc-2.6 tree
powerpc-ppc64_defconfig-xbuild
sparc64-defconfig-xbuild
sparc-defconfig-xbuild
um-x86_64-defconfig-xbuild
x86_64-defconfig-xbuild

notable exception: alpha (assembler errors, guess binutils funkyness)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
include/asm-alpha/atomic.h | 51 ++++++++++++
include/asm-generic/atomic.h | 169 +++++++++++++++++++++++++++++++++++++++++++
include/asm-i386/atomic.h | 7 +
include/asm-ia64/atomic.h | 25 +++++-
include/asm-mips/atomic.h | 28 ++++++-
include/asm-parisc/atomic.h | 29 ++++++-
include/asm-powerpc/atomic.h | 40 +++++++++-
include/asm-powerpc/bitops.h | 1
include/asm-powerpc/system.h | 1
include/asm-sparc64/atomic.h | 25 +++++-
include/asm-x86_64/atomic.h | 38 ++++++++-
11 files changed, 392 insertions(+), 22 deletions(-)

Index: linux-2.6/include/asm-alpha/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-alpha/atomic.h
+++ linux-2.6/include/asm-alpha/atomic.h
@@ -175,19 +175,64 @@ static __inline__ long atomic64_sub_retu
return result;
}

-#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
+#define atomic64_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), old, new))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
+#define atomic_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), old, new))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

+/**
+ * atomic_add_unless - add unless the number is a given value
+ * @v: pointer of type atomic_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * 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; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
- while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
+ for (;;) { \
+ if (unlikely(c == (u))) \
+ break; \
+ old = atomic_cmpxchg((v), c, c + (a)); \
+ if (likely(old == c)) \
+ break; \
c = old; \
+ } \
c != (u); \
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)

+/**
+ * atomic64_add_unless - add unless the number is a given value
+ * @v: pointer of type atomic64_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, so long as it was not @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+#define atomic64_add_unless(v, a, u) \
+({ \
+ __typeof__((v)->counter) 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; \
+ } \
+ c != (u); \
+})
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
#define atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0)
#define atomic64_add_negative(a, v) (atomic64_add_return((a), (v)) < 0)

Index: linux-2.6/include/asm-generic/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-generic/atomic.h
+++ linux-2.6/include/asm-generic/atomic.h
@@ -8,6 +8,7 @@
* edit all arch specific atomic.h files.
*/

+#include <asm/system.h>
#include <asm/types.h>

/*
@@ -66,6 +67,90 @@ static inline void atomic_long_sub(long
atomic64_sub(i, v);
}

+static inline int atomic_long_sub_and_test(long i, atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return atomic64_sub_and_test(i, v);
+}
+
+static inline int atomic_long_dec_and_test(atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return atomic64_dec_and_test(v);
+}
+
+static inline int atomic_long_inc_and_test(atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return atomic64_inc_and_test(v);
+}
+
+static inline int atomic_long_add_negative(long i, atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return atomic64_add_negative(i, v);
+}
+
+static inline long atomic_long_add_return(long i, atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_add_return(i, v);
+}
+
+static inline long atomic_long_sub_return(long i, atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_sub_return(i, v);
+}
+
+static inline long atomic_long_inc_return(atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_inc_return(v);
+}
+
+static inline long atomic_long_dec_return(atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_dec_return(v);
+}
+
+static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_add_unless(v, a, u);
+}
+
+static inline long atomic_long_inc_not_zero(atomic_long_t *l)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_inc_not_zero(v);
+}
+
+static inline long atomic_long_cmpxchg(atomic_long_t *l, long old, long new)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_cmpxchg(v, old, new);
+}
+
+static inline long atomic_long_xchg(atomic_long_t *l, long new)
+{
+ atomic64_t *v = (atomic64_t *)l;
+
+ return (long)atomic64_xchg(v, new);
+}
+
#else /* BITS_PER_LONG == 64 */

typedef atomic_t atomic_long_t;
@@ -113,6 +198,90 @@ static inline void atomic_long_sub(long
atomic_sub(i, v);
}

+static inline int atomic_long_sub_and_test(long i, atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return atomic_sub_and_test(i, v);
+}
+
+static inline int atomic_long_dec_and_test(atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return atomic_dec_and_test(v);
+}
+
+static inline int atomic_long_inc_and_test(atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return atomic_inc_and_test(v);
+}
+
+static inline int atomic_long_add_negative(long i, atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return atomic_add_negative(i, v);
+}
+
+static inline long atomic_long_add_return(long i, atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_add_return(i, v);
+}
+
+static inline long atomic_long_sub_return(long i, atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_sub_return(i, v);
+}
+
+static inline long atomic_long_inc_return(atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_inc_return(v);
+}
+
+static inline long atomic_long_dec_return(atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_dec_return(v);
+}
+
+static inline long atomic_long_add_unless(atomic_long_t *l, long a, long u)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_add_unless(v, a, u);
+}
+
+static inline long atomic_long_inc_not_zero(atomic_long_t *l)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_inc_not_zero(v);
+}
+
+static inline long atomic_long_cmpxchg(atomic_long_t *l, long old, long new)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_cmpxchg(v, old, new);
+}
+
+static inline long atomic_long_xchg(atomic_long_t *l, long new)
+{
+ atomic_t *v = (atomic_t *)l;
+
+ return (long)atomic_xchg(v, new);
+}
+
#endif /* BITS_PER_LONG == 64 */

#endif /* _ASM_GENERIC_ATOMIC_H */
Index: linux-2.6/include/asm-i386/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-i386/atomic.h
+++ linux-2.6/include/asm-i386/atomic.h
@@ -207,8 +207,9 @@ static __inline__ int atomic_sub_return(
return atomic_add_return(-i,v);
}

-#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
-#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (old), (new)))
+#define atomic_xchg(v, new) (xchg(&((v)->counter), (new)))

/**
* atomic_add_unless - add unless the number is a given value
@@ -221,7 +222,7 @@ static __inline__ int atomic_sub_return(
*/
#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
for (;;) { \
if (unlikely(c == (u))) \
Index: linux-2.6/include/asm-ia64/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-ia64/atomic.h
+++ linux-2.6/include/asm-ia64/atomic.h
@@ -88,12 +88,17 @@ ia64_atomic64_sub (__s64 i, atomic64_t *
return new;
}

-#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
+#define atomic_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), old, new))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

+#define atomic64_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), old, new))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__(v->counter) c, old; \
c = atomic_read(v); \
for (;;) { \
if (unlikely(c == (u))) \
@@ -107,6 +112,22 @@ ia64_atomic64_sub (__s64 i, atomic64_t *
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)

+#define atomic64_add_unless(v, a, u) \
+({ \
+ __typeof__(v->counter) 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; \
+ } \
+ c != (u); \
+})
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
#define atomic_add_return(i,v) \
({ \
int __ia64_aar_i = (i); \
Index: linux-2.6/include/asm-mips/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-mips/atomic.h
+++ linux-2.6/include/asm-mips/atomic.h
@@ -291,8 +291,8 @@ static __inline__ int atomic_sub_if_posi
return result;
}

-#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
-#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
+#define atomic_xchg(v, new) (xchg(&((v)->counter), (new)))

/**
* atomic_add_unless - add unless the number is a given value
@@ -305,7 +305,7 @@ static __inline__ int atomic_sub_if_posi
*/
#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
@@ -651,6 +651,28 @@ static __inline__ long atomic64_sub_if_p
return result;
}

+#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), (new)))
+
+/**
+ * atomic64_add_unless - add unless the number is a given value
+ * @v: pointer of type atomic64_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, so long as it was not @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+#define atomic64_add_unless(v, a, u) \
+({ \
+ __typeof__((v)->counter) c, old; \
+ c = atomic_read(v); \
+ while (c != (u) && (old = atomic64_cmpxchg((v), c, c + (a))) != c) \
+ c = old; \
+ c != (u); \
+})
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
#define atomic64_dec_return(v) atomic64_sub_return(1,(v))
#define atomic64_inc_return(v) atomic64_add_return(1,(v))

Index: linux-2.6/include/asm-parisc/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-parisc/atomic.h
+++ linux-2.6/include/asm-parisc/atomic.h
@@ -163,7 +163,8 @@ static __inline__ int atomic_read(const
}

/* exported interface */
-#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
+#define atomic_cmpxchg(v, o, n) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

/**
@@ -177,7 +178,7 @@ static __inline__ int atomic_read(const
*/
#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
while (c != (u) && (old = atomic_cmpxchg((v), c, c + (a))) != c) \
c = old; \
@@ -270,6 +271,30 @@ atomic64_read(const atomic64_t *v)
#define atomic64_dec_and_test(v) (atomic64_dec_return(v) == 0)
#define atomic64_sub_and_test(i,v) (atomic64_sub_return((i),(v)) == 0)

+/* exported interface */
+#define atomic64_cmpxchg(v, o, n) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
+/**
+ * atomic64_add_unless - add unless the number is a given value
+ * @v: pointer of type atomic64_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, so long as it was not @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+#define atomic64_add_unless(v, a, u) \
+({ \
+ __typeof__((v)->counter) c, old; \
+ c = atomic64_read(v); \
+ while (c != (u) && (old = atomic64_cmpxchg((v), c, c + (a))) != c) \
+ c = old; \
+ c != (u); \
+})
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
#endif /* CONFIG_64BIT */

#include <asm-generic/atomic.h>
Index: linux-2.6/include/asm-powerpc/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/atomic.h
+++ linux-2.6/include/asm-powerpc/atomic.h
@@ -165,7 +165,8 @@ static __inline__ int atomic_dec_return(
return t;
}

-#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
+#define atomic_cmpxchg(v, o, n) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

/**
@@ -413,6 +414,43 @@ static __inline__ long atomic64_dec_if_p
return t;
}

+#define atomic64_cmpxchg(v, o, n) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
+/**
+ * atomic64_add_unless - add unless the number is a given value
+ * @v: pointer of type atomic64_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, so long as it was not @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
+{
+ long t;
+
+ __asm__ __volatile__ (
+ LWSYNC_ON_SMP
+"1: ldarx %0,0,%1 # atomic_add_unless\n\
+ cmpd 0,%0,%3 \n\
+ beq- 2f \n\
+ add %0,%2,%0 \n"
+" stdcx. %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 atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
#endif /* __powerpc64__ */

#include <asm-generic/atomic.h>
Index: linux-2.6/include/asm-powerpc/bitops.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/bitops.h
+++ linux-2.6/include/asm-powerpc/bitops.h
@@ -39,7 +39,6 @@
#ifdef __KERNEL__

#include <linux/compiler.h>
-#include <asm/atomic.h>
#include <asm/asm-compat.h>
#include <asm/synch.h>

Index: linux-2.6/include/asm-powerpc/system.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/system.h
+++ linux-2.6/include/asm-powerpc/system.h
@@ -7,7 +7,6 @@
#include <linux/kernel.h>

#include <asm/hw_irq.h>
-#include <asm/atomic.h>

/*
* Memory barrier.
Index: linux-2.6/include/asm-sparc64/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-sparc64/atomic.h
+++ linux-2.6/include/asm-sparc64/atomic.h
@@ -70,12 +70,13 @@ extern int atomic64_sub_ret(int, atomic6
#define atomic_add_negative(i, v) (atomic_add_ret(i, v) < 0)
#define atomic64_add_negative(i, v) (atomic64_add_ret(i, v) < 0)

-#define atomic_cmpxchg(v, o, n) ((int)cmpxchg(&((v)->counter), (o), (n)))
+#define atomic_cmpxchg(v, o, n) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
for (;;) { \
if (unlikely(c == (u))) \
@@ -89,6 +90,26 @@ extern int atomic64_sub_ret(int, atomic6
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)

+#define atomic64_cmpxchg(v, o, n) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), (o), (n)))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
+#define atomic64_add_unless(v, a, u) \
+({ \
+ __typeof__((v)->counter) 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; \
+ } \
+ likely(c != (u)); \
+})
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
/* Atomic operations are already serializing */
#ifdef CONFIG_SMP
#define smp_mb__before_atomic_dec() membar_storeload_loadload();
Index: linux-2.6/include/asm-x86_64/atomic.h
===================================================================
--- linux-2.6.orig/include/asm-x86_64/atomic.h
+++ linux-2.6/include/asm-x86_64/atomic.h
@@ -375,8 +375,8 @@ static __inline__ long atomic64_add_retu
long __i = i;
__asm__ __volatile__(
LOCK_PREFIX "xaddq %0, %1;"
- :"=r"(i)
- :"m"(v->counter), "0"(i));
+ :"+r" (i), "+m" (v->counter)
+ : : "memory");
return i + __i;
}

@@ -388,7 +388,12 @@ static __inline__ long atomic64_sub_retu
#define atomic64_inc_return(v) (atomic64_add_return(1,v))
#define atomic64_dec_return(v) (atomic64_sub_return(1,v))

-#define atomic_cmpxchg(v, old, new) ((int)cmpxchg(&((v)->counter), old, new))
+#define atomic64_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), old, new))
+#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+
+#define atomic_cmpxchg(v, old, new) \
+ ((__typeof__((v)->counter))cmpxchg(&((v)->counter), old, new))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

/**
@@ -402,7 +407,7 @@ static __inline__ long atomic64_sub_retu
*/
#define atomic_add_unless(v, a, u) \
({ \
- int c, old; \
+ __typeof__((v)->counter) c, old; \
c = atomic_read(v); \
for (;;) { \
if (unlikely(c == (u))) \
@@ -416,6 +421,31 @@ static __inline__ long atomic64_sub_retu
})
#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)

+/**
+ * atomic64_add_unless - add unless the number is a given value
+ * @v: pointer of type atomic64_t
+ * @a: the amount to add to v...
+ * @u: ...unless v is equal to u.
+ *
+ * Atomically adds @a to @v, so long as it was not @u.
+ * Returns non-zero if @v was not @u, and zero otherwise.
+ */
+#define atomic64_add_unless(v, a, u) \
+({ \
+ __typeof__((v)->counter) 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; \
+ } \
+ c != (u); \
+})
+#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)
+
/* These are x86-specific, used by some header files */
#define atomic_clear_mask(mask, addr) \
__asm__ __volatile__(LOCK_PREFIX "andl %0,%1" \