ARM: fix PTRACE_SETVFPREGS on SMP systems

PTRACE_SETVFPREGS fails to properly mark the VFP register set to be
reloaded, because it undoes one of the effects of vfp_flush_hwstate().

Specifically vfp_flush_hwstate() sets thread->vfpstate.hard.cpu to
an invalid CPU number, but vfp_set() overwrites this with the original
CPU number, thereby rendering the hardware state as apparently "valid",
even though the software state is more recent.

Fix this by reverting the previous change.

Cc: <[email protected]>
Fixes: 8130b9d ("ARM: 7308/1: vfp: flush thread hwstate before copying ptrace registers")
Acked-by: Will Deacon <[email protected]>
Tested-by: Simon Marchi <[email protected]>
Signed-off-by: Russell King <[email protected]>

Author: Russell King

arch/arm/kernel/ptrace.c

@@ -733,8 +733,8 @@ static int vfp_set(struct task_struct *target,
 	if (ret)
 		return ret;
 
-	vfp_flush_hwstate(thread);
 	thread->vfpstate.hard = new_vfp;
+	vfp_flush_hwstate(thread);
 
 	return 0;
 }