Re: [PATCH 2/2] tracing/function-graph-tracer: improve durationoutput

From: Steven Rostedt
Date: Wed Dec 03 2008 - 11:32:07 EST

On Wed, 3 Dec 2008, Fr?d?ric Weisbecker wrote:
> A proposition about this. I want to use __ftrace_printk, make it
> generic for both function tracers and have a way to store the current
> depth.
> One solution: changing the print_entry to have the ip available for
> function-tracer and depth available for return-function_tracer.
> struct print_entry {
> struct trace_entry ent;
> union {
> unsigned long ip;
> unsigned long depth;
> } from;
> char buf[];
> };
> We could make __ftrace_printk verify which tracer is running.
> If normal tracer then
> trace_vprintk(__builtin_return_address(0), .....)
> else if graph-tracer
> trace_vprintk(current->curr_ret_stack, ......)
> This way we can even forget the ip argument of __trace_printk.
> I prefer to ask before changing an exported symbol API....

Actually, I would prefer to keep both.

struct print_entry {
struct trace_entry ent;
unsigned long ip;
int depth;
char buf[];

And pass in both. Have the readers of the functions figure out what to do
with either, and keep the messiness away from the API.

-- Steve

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