[PATCH] lightweight robust futexes: x86_64

x86_64: add the futex_atomic_cmpxchg_inuser() assembly implementation, and
wire up the new syscalls.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Acked-by: Ulrich Drepper <drepper@redhat.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/ia32/ia32entry.S

@@ -688,6 +688,8 @@ ia32_sys_call_table:
 	.quad sys_ni_syscall		/* pselect6 for now */
 	.quad sys_ni_syscall		/* ppoll for now */
 	.quad sys_unshare		/* 310 */
+	.quad compat_sys_set_robust_list
+	.quad compat_sys_get_robust_list
 ia32_syscall_end:		
 	.rept IA32_NR_syscalls-(ia32_syscall_end-ia32_sys_call_table)/8
 		.quad ni_syscall

include/asm-x86_64/futex.h

@@ -97,7 +97,28 @@ futex_atomic_op_inuser (int encoded_op, int __user *uaddr)
 static inline int
 futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
 {
-	return -ENOSYS;
+	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+		return -EFAULT;
+
+	__asm__ __volatile__(
+		"1:	" LOCK_PREFIX "cmpxchgl %3, %1		\n"
+
+		"2:	.section .fixup, \"ax\"			\n"
+		"3:	mov     %2, %0				\n"
+		"	jmp     2b				\n"
+		"	.previous				\n"
+
+		"	.section __ex_table, \"a\"		\n"
+		"	.align  8				\n"
+		"	.quad   1b,3b				\n"
+		"	.previous				\n"
+
+		: "=a" (oldval), "=m" (*uaddr)
+		: "i" (-EFAULT), "r" (newval), "0" (oldval)
+		: "memory"
+	);
+
+	return oldval;
 }
 
 #endif

include/asm-x86_64/unistd.h

@@ -605,8 +605,12 @@ __SYSCALL(__NR_pselect6, sys_ni_syscall)	/* for now */
 __SYSCALL(__NR_ppoll,	sys_ni_syscall)		/* for now */
 #define __NR_unshare		272
 __SYSCALL(__NR_unshare,	sys_unshare)
+#define __NR_set_robust_list	273
+__SYSCALL(__NR_set_robust_list, sys_set_robust_list)
+#define __NR_get_robust_list	274
+__SYSCALL(__NR_get_robust_list, sys_get_robust_list)
 
-#define __NR_syscall_max __NR_unshare
+#define __NR_syscall_max __NR_get_robust_list
 
 #ifndef __NO_STUBS