ARC: Add llock/scond to futex backend

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/futex.h

@@ -16,6 +16,34 @@
 #include <linux/uaccess.h>
 #include <asm/errno.h>
 
+#ifdef CONFIG_ARC_HAS_LLSC
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)\
+							\
+	__asm__ __volatile__(				\
+	"1:	llock	%1, [%2]		\n"	\
+		insn				"\n"	\
+	"2:	scond	%0, [%2]		\n"	\
+	"	bnz	1b			\n"	\
+	"	mov %0, 0			\n"	\
+	"3:					\n"	\
+	"	.section .fixup,\"ax\"		\n"	\
+	"	.align  4			\n"	\
+	"4:	mov %0, %4			\n"	\
+	"	b   3b				\n"	\
+	"	.previous			\n"	\
+	"	.section __ex_table,\"a\"	\n"	\
+	"	.align  4			\n"	\
+	"	.word   1b, 4b			\n"	\
+	"	.word   2b, 4b			\n"	\
+	"	.previous			\n"	\
+							\
+	: "=&r" (ret), "=&r" (oldval)			\
+	: "r" (uaddr), "r" (oparg), "ir" (-EFAULT)	\
+	: "cc", "memory")
+
+#else	/* !CONFIG_ARC_HAS_LLSC */
+
 #define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)\
 							\
 	__asm__ __volatile__(				\
@@ -39,6 +67,8 @@
 	: "r" (uaddr), "r" (oparg), "ir" (-EFAULT)	\
 	: "cc", "memory")
 
+#endif
+
 static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
 {
 	int op = (encoded_op >> 28) & 7;
@@ -123,11 +153,17 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 oldval,
 
 	pagefault_disable();
 
-	/* TBD : can use llock/scond */
 	__asm__ __volatile__(
+#ifdef CONFIG_ARC_HAS_LLSC
+	"1:	llock	%0, [%3]		\n"
+	"	brne	%0, %1, 3f		\n"
+	"2:	scond	%2, [%3]		\n"
+	"	bnz	1b			\n"
+#else
 	"1:	ld	%0, [%3]		\n"
 	"	brne	%0, %1, 3f		\n"
 	"2:	st	%2, [%3]		\n"
+#endif
 	"3:	\n"
 	"	.section .fixup,\"ax\"	\n"
 	"4:	mov %0, %4	\n"