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Subject[tip:perfcounters/core] x86, perfcounters: add atomic64_xchg()
Commit-ID:  98c2aaf8be5baf7193be37fb28bce8e7327158bc
Gitweb: http://git.kernel.org/tip/98c2aaf8be5baf7193be37fb28bce8e7327158bc
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Tue, 7 Apr 2009 11:30:17 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Tue, 7 Apr 2009 12:02:41 +0200

x86, perfcounters: add atomic64_xchg()

Complete atomic64_t support on the 32-bit side by adding atomic64_xch().

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090406094518.445450972@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
arch/x86/include/asm/atomic_32.h | 24 +++++++++++++++++++++---
1 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h
index 977250e..aff9f1f 100644
--- a/arch/x86/include/asm/atomic_32.h
+++ b/arch/x86/include/asm/atomic_32.h
@@ -291,19 +291,37 @@ atomic64_cmpxchg(atomic64_t *ptr, unsigned long long old_val,
}

/**
- * atomic64_set - set atomic64 variable
+ * atomic64_xchg - xchg atomic64 variable
* @ptr: pointer to type atomic64_t
* @new_val: value to assign
+ * @old_val: old value that was there
*
- * Atomically sets the value of @ptr to @new_val.
+ * Atomically xchgs the value of @ptr to @new_val and returns
+ * the old value.
*/
-static inline void atomic64_set(atomic64_t *ptr, unsigned long long new_val)
+
+static inline unsigned long long
+atomic64_xchg(atomic64_t *ptr, unsigned long long new_val)
{
unsigned long long old_val;

do {
old_val = atomic_read(ptr);
} while (atomic64_cmpxchg(ptr, old_val, new_val) != old_val);
+
+ return old_val;
+}
+
+/**
+ * atomic64_set - set atomic64 variable
+ * @ptr: pointer to type atomic64_t
+ * @new_val: value to assign
+ *
+ * Atomically sets the value of @ptr to @new_val.
+ */
+static inline void atomic64_set(atomic64_t *ptr, unsigned long long new_val)
+{
+ atomic64_xchg(ptr, new_val);
}

/**

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