2 files changed, 87 insertions, 0 deletions
diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h
new file mode 100644
index 00000000000..b2ba2fc8829
--- /dev/null
+++ b/include/asm-generic/cmpxchg-local.h
@@ -0,0 +1,65 @@
+#ifndef __ASM_GENERIC_CMPXCHG_LOCAL_H
+#define __ASM_GENERIC_CMPXCHG_LOCAL_H
+
+#include <linux/types.h>
+
+extern unsigned long wrong_size_cmpxchg(volatile void *ptr);
+
+/*
+ * Generic version of __cmpxchg_local (disables interrupts). Takes an unsigned
+ * long parameter, supporting various types of architectures.
+ */
+static inline unsigned long __cmpxchg_local_generic(volatile void *ptr,
+		unsigned long old, unsigned long new, int size)
+{
+	unsigned long flags, prev;
+
+	/*
+	 * Sanity checking, compile-time.
+	 */
+	if (size == 8 && sizeof(unsigned long) != 8)
+		wrong_size_cmpxchg(ptr);
+
+	local_irq_save(flags);
+	switch (size) {
+	case 1: prev = *(u8 *)ptr;
+		if (prev == old)
+			*(u8 *)ptr = (u8)new;
+		break;
+	case 2: prev = *(u16 *)ptr;
+		if (prev == old)
+			*(u16 *)ptr = (u16)new;
+		break;
+	case 4: prev = *(u32 *)ptr;
+		if (prev == old)
+			*(u32 *)ptr = (u32)new;
+		break;
+	case 8: prev = *(u64 *)ptr;
+		if (prev == old)
+			*(u64 *)ptr = (u64)new;
+		break;
+	default:
+		wrong_size_cmpxchg(ptr);
+	}
+	local_irq_restore(flags);
+	return prev;
+}
+
+/*
+ * Generic version of __cmpxchg64_local. Takes an u64 parameter.
+ */
+static inline u64 __cmpxchg64_local_generic(volatile void *ptr,
+		u64 old, u64 new)
+{
+	u64 prev;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	prev = *(u64 *)ptr;
+	if (prev == old)
+		*(u64 *)ptr = new;
+	local_irq_restore(flags);
+	return prev;
+}
+
+#endif
diff --git a/include/asm-generic/cmpxchg.h b/include/asm-generic/cmpxchg.h
new file mode 100644
index 00000000000..213ac6e8fe3
--- /dev/null
+++ b/include/asm-generic/cmpxchg.h
@@ -0,0 +1,22 @@
+#ifndef __ASM_GENERIC_CMPXCHG_H
+#define __ASM_GENERIC_CMPXCHG_H
+
+/*
+ * Generic cmpxchg
+ *
+ * Uses the local cmpxchg. Does not support SMP.
+ */
+#ifdef CONFIG_SMP
+#error "Cannot use generic cmpxchg on SMP"
+#endif
+
+/*
+ * Atomic compare and exchange.
+ *
+ * Do not define __HAVE_ARCH_CMPXCHG because we want to use it to check whether
+ * a cmpxchg primitive faster than repeated local irq save/restore exists.
+ */
+#define cmpxchg(ptr, o, n)	cmpxchg_local((ptr), (o), (n))
+#define cmpxchg64(ptr, o, n)	cmpxchg64_local((ptr), (o), (n))
+
+#endif