Merge branch 'tracing-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[karo-tx-linux.git] / kernel / trace / ftrace.c

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index d6973dfadb36d4b46aec2546d69a8766d5c753f8..bb60732ade0cc7bca54fdbff32a9dfda16bacde9 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3218,12 +3218,12 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
                }
 
                if (t->ret_stack == NULL) {
-                       t->curr_ret_stack = -1;
-                       /* Make sure IRQs see the -1 first: */
-                       barrier();
-                       t->ret_stack = ret_stack_list[start++];
                        atomic_set(&t->tracing_graph_pause, 0);
                        atomic_set(&t->trace_overrun, 0);
+                       t->curr_ret_stack = -1;
+                       /* Make sure the tasks see the -1 first: */
+                       smp_wmb();
+                       t->ret_stack = ret_stack_list[start++];
                }
        } while_each_thread(g, t);
 
@@ -3281,8 +3281,10 @@ static int start_graph_tracing(void)
                return -ENOMEM;
 
        /* The cpu_boot init_task->ret_stack will never be freed */
-       for_each_online_cpu(cpu)
-               ftrace_graph_init_task(idle_task(cpu));
+       for_each_online_cpu(cpu) {
+               if (!idle_task(cpu)->ret_stack)
+                       ftrace_graph_init_task(idle_task(cpu));
+       }
 
        do {
                ret = alloc_retstack_tasklist(ret_stack_list);
@@ -3374,18 +3376,25 @@ void unregister_ftrace_graph(void)
 /* Allocate a return stack for newly created task */
 void ftrace_graph_init_task(struct task_struct *t)
 {
+       /* Make sure we do not use the parent ret_stack */
+       t->ret_stack = NULL;
+
        if (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;
-       } else
-               t->ret_stack = NULL;
+               /* make curr_ret_stack visable before we add the ret_stack */
+               smp_wmb();
+               t->ret_stack = ret_stack;
+       }
 }
 
 void ftrace_graph_exit_task(struct task_struct *t)