[IA64] Fix the order of atomic operations in restore_previous_kprobes on ia64

Fix the order of atomic operations to prevent overwriting prev_kprobe[0].
To pop values from stack, we must decrement stack index right AFTER
reading values.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index fc4d2676264f..b618487cdc85 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -381,9 +381,10 @@ static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
 {
         unsigned int i;
-        i = atomic_sub_return(1, &kcb->prev_kprobe_index);
-        __get_cpu_var(current_kprobe) = kcb->prev_kprobe[i].kp;
-        kcb->kprobe_status = kcb->prev_kprobe[i].status;
+        i = atomic_read(&kcb->prev_kprobe_index);
+        __get_cpu_var(current_kprobe) = kcb->prev_kprobe[i-1].kp;
+        kcb->kprobe_status = kcb->prev_kprobe[i-1].status;
+        atomic_sub(1, &kcb->prev_kprobe_index);
 }
 
 static void __kprobes set_current_kprobe(struct kprobe *p,