[SPARC]: Emulate cmpxchg like parisc

Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c
index 559335f4917d..617d29832e19 100644
--- a/arch/sparc/lib/atomic32.c
+++ b/arch/sparc/lib/atomic32.c
@@ -2,6 +2,7 @@
  * atomic32.c: 32-bit atomic_t implementation
  *
  * Copyright (C) 2004 Keith M Wesolowski
+ * Copyright (C) 2007 Kyle McMartin
  * 
  * Based on asm-parisc/atomic.h Copyright (C) 2000 Philipp Rumpf
  */
@@ -117,3 +118,17 @@ unsigned long ___change_bit(unsigned long *addr, unsigned long mask)
         return old & mask;
 }
 EXPORT_SYMBOL(___change_bit);
+
+unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new)
+{
+        unsigned long flags;
+        u32 prev;
+
+        spin_lock_irqsave(ATOMIC_HASH(addr), flags);
+        if ((prev = *ptr) == old)
+                *ptr = new;
+        spin_unlock_irqrestore(ATOMIC_HASH(addr), flags);
+
+        return (unsigned long)prev;
+}
+EXPORT_SYMBOL(__cmpxchg_u32);