ARC: change return value of userspace cmpxchg assist syscall

[linux-2.6-microblaze.git] / arch / arc / kernel / process.c

diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index 59aa43c..a41a79a 100644 (file)
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -43,8 +43,8 @@ SYSCALL_DEFINE0(arc_gettls)
 
 SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
 {
-       int uval;
-       int ret;
+       struct pt_regs *regs = current_pt_regs();
+       int uval = -EFAULT;
 
        /*
         * This is only for old cores lacking LLOCK/SCOND, which by defintion
@@ -54,24 +54,26 @@ SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
         */
        WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
 
+       /* Z indicates to userspace if operation succeded */
+       regs->status32 &= ~STATUS_Z_MASK;
+
        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
                return -EFAULT;
 
        preempt_disable();
 
-       ret = __get_user(uval, uaddr);
-       if (ret)
+       if (__get_user(uval, uaddr))
                goto done;
 
-       if (uval != expected)
-               ret = -EAGAIN;
-       else
-               ret = __put_user(new, uaddr);
+       if (uval == expected) {
+               if (!__put_user(new, uaddr))
+                       regs->status32 |= STATUS_Z_MASK;
+       }
 
 done:
        preempt_enable();
 
-       return ret;
+       return uval;
 }
 
 void arch_cpu_idle(void)