[PATCH 4/4] ARM: atomics: don't use exclusives for atomic64 read/set with LPAE
Will Deacon
will.deacon at arm.com
Mon Mar 25 14:19:41 EDT 2013
To ease page table updates with 64-bit descriptors, CPUs implementing
LPAE are required to implement ldrd/strd as atomic operations.
This patch uses these accessors instead of the exclusive variants when
performing atomic64_{read,set} on LPAE systems.
Signed-off-by: Will Deacon <will.deacon at arm.com>
---
arch/arm/include/asm/atomic.h | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
index c79f61f..da1c77d 100644
--- a/arch/arm/include/asm/atomic.h
+++ b/arch/arm/include/asm/atomic.h
@@ -243,6 +243,29 @@ typedef struct {
#define ATOMIC64_INIT(i) { (i) }
+#ifdef CONFIG_ARM_LPAE
+static inline u64 atomic64_read(const atomic64_t *v)
+{
+ u64 result;
+
+ __asm__ __volatile__("@ atomic64_read\n"
+" ldrd %0, %H0, [%1]"
+ : "=&r" (result)
+ : "r" (&v->counter), "Qo" (v->counter)
+ );
+
+ return result;
+}
+
+static inline void atomic64_set(atomic64_t *v, u64 i)
+{
+ __asm__ __volatile__("@ atomic64_set\n"
+" strd %2, %H2, [%1]"
+ : "=Qo" (v->counter)
+ : "r" (&v->counter), "r" (i)
+ );
+}
+#else
static inline u64 atomic64_read(const atomic64_t *v)
{
u64 result;
@@ -269,6 +292,7 @@ static inline void atomic64_set(atomic64_t *v, u64 i)
: "r" (&v->counter), "r" (i)
: "cc");
}
+#endif
static inline void atomic64_add(u64 i, atomic64_t *v)
{
--
1.8.0
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