x86: Unify rwlock assembly implementation

Rather than having two functionally identical implementations
for 32- and 64-bit configurations, extend the existing assembly
abstractions enough to fold the two rwlock implementations into
a shared one.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/4E258DD7020000780004E3EA@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/lib/rwlock.S b/arch/x86/lib/rwlock.S
new file mode 100644
index 0000000..fca1782
--- /dev/null
+++ b/arch/x86/lib/rwlock.S
@@ -0,0 +1,44 @@
+/* Slow paths of read/write spinlocks. */
+
+#include <linux/linkage.h>
+#include <asm/alternative-asm.h>
+#include <asm/frame.h>
+#include <asm/rwlock.h>
+
+#ifdef CONFIG_X86_32
+# define __lock_ptr eax
+#else
+# define __lock_ptr rdi
+#endif
+
+ENTRY(__write_lock_failed)
+	CFI_STARTPROC
+	FRAME
+0:	LOCK_PREFIX
+	addl	$RW_LOCK_BIAS, (%__lock_ptr)
+1:	rep; nop
+	cmpl	$RW_LOCK_BIAS, (%__lock_ptr)
+	jne	1b
+	LOCK_PREFIX
+	subl	$RW_LOCK_BIAS, (%__lock_ptr)
+	jnz	0b
+	ENDFRAME
+	ret
+	CFI_ENDPROC
+END(__write_lock_failed)
+
+ENTRY(__read_lock_failed)
+	CFI_STARTPROC
+	FRAME
+0:	LOCK_PREFIX
+	incl	(%__lock_ptr)
+1:	rep; nop
+	cmpl	$1, (%__lock_ptr)
+	js	1b
+	LOCK_PREFIX
+	decl	(%__lock_ptr)
+	js	0b
+	ENDFRAME
+	ret
+	CFI_ENDPROC
+END(__read_lock_failed)