ftrace: add stack trace to function tracer
Impact: new feature to stack trace any function
Chris Mason asked about being able to pick and choose a function
and get a stack trace from it. This feature enables his request.
# echo io_schedule > /debug/tracing/set_ftrace_filter
# echo function > /debug/tracing/current_tracer
# echo func_stack_trace > /debug/tracing/trace_options
Produces the following in /debug/tracing/trace:
kjournald-702 [001] 135.673060: io_schedule <-sync_buffer
kjournald-702 [002] 135.673671:
<= sync_buffer
<= __wait_on_bit
<= out_of_line_wait_on_bit
<= __wait_on_buffer
<= sync_dirty_buffer
<= journal_commit_transaction
<= kjournald
Note, be careful about turning this on without filtering the functions.
You may find that you have a 10 second lag between typing and seeing
what you typed. This is why the stack trace for the function tracer
does not use the same stack_trace flag as the other tracers use.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 79c8721..bf39a36 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -457,6 +457,11 @@
void update_max_tr_single(struct trace_array *tr,
struct task_struct *tsk, int cpu);
+void __trace_stack(struct trace_array *tr,
+ struct trace_array_cpu *data,
+ unsigned long flags,
+ int skip, int pc);
+
extern cycle_t ftrace_now(int cpu);
#ifdef CONFIG_FUNCTION_TRACER
@@ -467,6 +472,8 @@
# define tracing_stop_function_trace() do { } while (0)
#endif
+extern int ftrace_function_enabled;
+
#ifdef CONFIG_CONTEXT_SWITCH_TRACER
typedef void
(*tracer_switch_func_t)(void *private,
