---

yaml
---
r: 146230
b: refs/heads/master
c: 82310a3
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 179c498ae2998461fe436437a74dc29036fc7dcc
+refs/heads/master: 82310a3272d5a2a7652f5649ad8a55f58c8f74d9

trunk/kernel/trace/ftrace.c

@@ -2739,15 +2739,20 @@ void unregister_ftrace_graph(void)
 void ftrace_graph_init_task(struct task_struct *t)
 {
 	if (atomic_read(&ftrace_graph_active)) {
-		t->ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
+		struct ftrace_ret_stack *ret_stack;
+
+		ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
 				* sizeof(struct ftrace_ret_stack),
 				GFP_KERNEL);
-		if (!t->ret_stack)
+		if (!ret_stack)
 			return;
 		t->curr_ret_stack = -1;
 		atomic_set(&t->tracing_graph_pause, 0);
 		atomic_set(&t->trace_overrun, 0);
 		t->ftrace_timestamp = 0;
+		/* make curr_ret_stack visable before we add the ret_stack */
+		smp_wmb();
+		t->ret_stack = ret_stack;
 	} else
 		t->ret_stack = NULL;
 }

trunk/kernel/trace/trace_functions_graph.c

@@ -65,6 +65,12 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth)
 	if (!current->ret_stack)
 		return -EBUSY;
 
+	/*
+	 * We must make sure the ret_stack is tested before we read
+	 * anything else.
+	 */
+	smp_rmb();
+
 	/* The return trace stack is full */
 	if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
 		atomic_inc(&current->trace_overrun);