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-rw-r--r--kernel/trace/ftrace.c52
1 files changed, 45 insertions, 7 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f3dadae..888b611 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3328,7 +3328,7 @@ static int start_graph_tracing(void)
/* The cpu_boot init_task->ret_stack will never be freed */
for_each_online_cpu(cpu) {
if (!idle_task(cpu)->ret_stack)
- ftrace_graph_init_task(idle_task(cpu));
+ ftrace_graph_init_idle_task(idle_task(cpu), cpu);
}
do {
@@ -3418,6 +3418,49 @@ void unregister_ftrace_graph(void)
mutex_unlock(&ftrace_lock);
}
+static DEFINE_PER_CPU(struct ftrace_ret_stack *, idle_ret_stack);
+
+static void
+graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack)
+{
+ 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;
+}
+
+/*
+ * Allocate a return stack for the idle task. May be the first
+ * time through, or it may be done by CPU hotplug online.
+ */
+void ftrace_graph_init_idle_task(struct task_struct *t, int cpu)
+{
+ t->curr_ret_stack = -1;
+ /*
+ * The idle task has no parent, it either has its own
+ * stack or no stack at all.
+ */
+ if (t->ret_stack)
+ WARN_ON(t->ret_stack != per_cpu(idle_ret_stack, cpu));
+
+ if (ftrace_graph_active) {
+ struct ftrace_ret_stack *ret_stack;
+
+ ret_stack = per_cpu(idle_ret_stack, cpu);
+ if (!ret_stack) {
+ ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
+ * sizeof(struct ftrace_ret_stack),
+ GFP_KERNEL);
+ if (!ret_stack)
+ return;
+ per_cpu(idle_ret_stack, cpu) = ret_stack;
+ }
+ graph_init_task(t, ret_stack);
+ }
+}
+
/* Allocate a return stack for newly created task */
void ftrace_graph_init_task(struct task_struct *t)
{
@@ -3433,12 +3476,7 @@ void ftrace_graph_init_task(struct task_struct *t)
GFP_KERNEL);
if (!ret_stack)
return;
- 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;
+ graph_init_task(t, ret_stack);
}
}