[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>

2 files changed, 27 insertions, 2 deletions

diff --git a/include/asm-x86_64/futex.h b/include/asm-x86_64/futex.h
index 4f4cb3410d06..7d9eb1a84546 100644
--- a/include/asm-x86_64/futex.h
+++ b/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
diff --git a/include/asm-x86_64/unistd.h b/include/asm-x86_64/unistd.h
index da0341c57949..fcc516353087 100644
--- a/include/asm-x86_64/unistd.h
+++ b/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