[PATCH] lightweight robust futexes: i386

i386: 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>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 27 insertions, 2 deletions

diff --git a/arch/i386/kernel/syscall_table.S b/arch/i386/kernel/syscall_table.S
index ac687d00a1ce..326595f3fa4d 100644
--- a/arch/i386/kernel/syscall_table.S
+++ b/arch/i386/kernel/syscall_table.S
@@ -310,3 +310,5 @@ ENTRY(sys_call_table)
         .long sys_pselect6
         .long sys_ppoll
         .long sys_unshare               /* 310 */
+        .long sys_set_robust_list
+        .long sys_get_robust_list
diff --git a/include/asm-i386/futex.h b/include/asm-i386/futex.h
index 1f39ad9d52a1..41184a31885c 100644
--- a/include/asm-i386/futex.h
+++ b/include/asm-i386/futex.h
@@ -107,7 +107,28 @@ 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"
+                "       .long   1b,3b                           \n"
+                "       .previous                               \n"
+
+                : "=a" (oldval), "=m" (*uaddr)
+                : "i" (-EFAULT), "r" (newval), "0" (oldval)
+                : "memory"
+        );
+
+        return oldval;
 }
 
 #endif
diff --git a/include/asm-i386/unistd.h b/include/asm-i386/unistd.h
index d8afd0e3b81a..014e3562895b 100644
--- a/include/asm-i386/unistd.h
+++ b/include/asm-i386/unistd.h
@@ -316,8 +316,10 @@
 #define __NR_pselect6           308
 #define __NR_ppoll              309
 #define __NR_unshare            310
+#define __NR_set_robust_list    311
+#define __NR_get_robust_list    312
 
-#define NR_syscalls 311
+#define NR_syscalls 313
 
 /*
  * user-visible error numbers are in the range -1 - -128: see