From 4a6dae6d382e9edf3ff440b819e554ed706359bc Mon Sep 17 00:00:00 2001
From: Nick Piggin <nickpiggin@yahoo.com.au>
Date: Sun, 13 Nov 2005 16:07:24 -0800
Subject: [PATCH] atomic: cmpxchg

Introduce an atomic_cmpxchg operation.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
 include/asm-sh/atomic.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

(limited to 'include/asm-sh')

diff --git a/include/asm-sh/atomic.h b/include/asm-sh/atomic.h
index 3c4f805da1a..a148c762d36 100644
--- a/include/asm-sh/atomic.h
+++ b/include/asm-sh/atomic.h
@@ -87,6 +87,20 @@ static __inline__ int atomic_sub_return(int i, atomic_t * v)
 #define atomic_inc(v) atomic_add(1,(v))
 #define atomic_dec(v) atomic_sub(1,(v))
 
+static inline int atomic_cmpxchg(atomic_t *v, int old, int new)
+{
+	int ret;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	ret = v->counter;
+	if (likely(ret == old))
+		v->counter = new;
+	local_irq_restore(flags);
+
+	return ret;
+}
+
 static __inline__ void atomic_clear_mask(unsigned int mask, atomic_t *v)
 {
 	unsigned long flags;
-- 
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