Implement xchg_relaxed and define atomic{,64}_xchg_* as xchg_relaxed,
based on these _relaxed variants, release/acquire variants can be built.
Note that xchg_relaxed and atomic_{,64}_xchg_relaxed are not compiler
barriers.
Signed-off-by: Boqun Feng <boqun.f...@gmail.com>
---
arch/powerpc/include/asm/atomic.h | 2 ++
arch/powerpc/include/asm/cmpxchg.h | 64 ++++++++++++++++++++++++++++++++++++++
2 files changed, 66 insertions(+)
diff --git a/arch/powerpc/include/asm/atomic.h
b/arch/powerpc/include/asm/atomic.h
index d1dcdcf..d9f570b 100644
--- a/arch/powerpc/include/asm/atomic.h
+++ b/arch/powerpc/include/asm/atomic.h
@@ -193,6 +193,7 @@ static __inline__ int atomic_dec_return(atomic_t *v)
#define atomic_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
/**
* __atomic_add_unless - add unless the number is a given value
@@ -461,6 +462,7 @@ static __inline__ long atomic64_dec_if_positive(atomic64_t
*v)
#define atomic64_cmpxchg(v, o, n) (cmpxchg(&((v)->counter), (o), (n)))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))
+#define atomic64_xchg_relaxed(v, new) xchg_relaxed(&((v)->counter), (new))
/**
* atomic64_add_unless - add unless the number is a given value
diff --git a/arch/powerpc/include/asm/cmpxchg.h
b/arch/powerpc/include/asm/cmpxchg.h
index ad6263c..66374f4 100644
--- a/arch/powerpc/include/asm/cmpxchg.h
+++ b/arch/powerpc/include/asm/cmpxchg.h
@@ -54,6 +54,32 @@ __xchg_u32_local(volatile void *p, unsigned long val)
return prev;
}
+/*
+ * Atomic exchange relaxed
+ *
+ * Changes the memory location '*p' to be val and returns
+ * the previous value stored there.
+ *
+ * Note that this is not a compiler barrier, there is no order
+ * guarantee around.
+ */
+static __always_inline unsigned long
+__xchg_u32_relaxed(u32 *p, unsigned long val)
+{
+ unsigned long prev;
+
+ __asm__ __volatile__(
+"1: lwarx %0,0,%2\n"
+ PPC405_ERR77(0, %2)
+" stwcx. %3,0,%2\n"
+" bne- 1b"
+ : "=&r" (prev), "+m" (*p)
+ : "r" (p), "r" (val)
+ : "cc");
+
+ return prev;
+}
+
#ifdef CONFIG_PPC64
static __always_inline unsigned long
__xchg_u64(volatile void *p, unsigned long val)
@@ -90,6 +116,23 @@ __xchg_u64_local(volatile void *p, unsigned long val)
return prev;
}
+
+static __always_inline unsigned long
+__xchg_u64_relaxed(u64 *p, unsigned long val)
+{
+ unsigned long prev;
+
+ __asm__ __volatile__(
+"1: ldarx %0,0,%2\n"
+ PPC405_ERR77(0, %2)
+" stdcx. %3,0,%2\n"
+" bne- 1b"
+ : "=&r" (prev), "+m" (*p)
+ : "r" (p), "r" (val)
+ : "cc");
+
+ return prev;
+}
#endif
/*
@@ -127,6 +170,21 @@ __xchg_local(volatile void *ptr, unsigned long x, unsigned
int size)
__xchg_called_with_bad_pointer();
return x;
}
+
+static __always_inline unsigned long
+__xchg_relaxed(void *ptr, unsigned long x, unsigned int size)
+{
+ switch (size) {
+ case 4:
+ return __xchg_u32_relaxed(ptr, x);
+#ifdef CONFIG_PPC64
+ case 8:
+ return __xchg_u64_relaxed(ptr, x);
+#endif
+ }
+ __xchg_called_with_bad_pointer();
+ return x;
+}
#define xchg(ptr,x) \
({ \
__typeof__(*(ptr)) _x_ = (x); \
@@ -140,6 +198,12 @@ __xchg_local(volatile void *ptr, unsigned long x, unsigned
int size)
(unsigned long)_x_, sizeof(*(ptr))); \
})
+#define xchg_relaxed(ptr, x) \
+({ \
+ __typeof__(*(ptr)) _x_ = (x); \
+ (__typeof__(*(ptr))) __xchg_relaxed((ptr), \
+ (unsigned long)_x_, sizeof(*(ptr))); \
+})
/*
* Compare and exchange - if *p == old, set it to new,
* and return the old value of *p.
--
2.5.1
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