Messages in this thread Patch in this message | | | Date | Wed, 9 Mar 2016 08:52:50 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 1/2] tracing: make tracer_flags use the right set_flag callback |
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On Wed, 9 Mar 2016 08:38:45 -0500 (EST) Chunyu Hu <chuhu@redhat.com> wrote:
> ----- Original Message ----- > > From: "Steven Rostedt" <rostedt@goodmis.org> > > To: "Chunyu Hu" <chuhu@redhat.com> > > Cc: liwan@redhat.com, linux-kernel@vger.kernel.org > > Sent: Wednesday, March 9, 2016 12:23:12 AM > > Subject: Re: [PATCH 1/2] tracing: make tracer_flags use the right set_flag callback > > > > On Tue, 8 Mar 2016 10:55:30 -0500 (EST) > > Chunyu Hu <chuhu@redhat.com> wrote: > > > > > > > Sure! But my patch/build work are all manual, so I guess I can't keep with > > > your speed, but i will do. Thx. > > > > Here's the latest version of your patch ;-) > > Thanks. It's amazing, all the call trace in ftrace.c are gone. I did > the ltp ftrace stress tests and some regression tests on it. I didn't hit > any call trace. Thanks for the modification of the code. Just hit several > dmesg like: kernel: failed to start wakeup tracer. > > > BTW, may I ask the question that what's the difference of func_stack_trace > and stacktrace? And Is there a case that the tracing_on can't be setup? I > haven't touch many parts of the code. Thanks ;)
stacktrace works with events, func_stack_trace works with the function tracer. They are separate for two reasons. One, they have completely different infrastructures. Two, function tracing is far more invasive, and enabling func_stack_trace without function filtering will pretty much bring your system to a screaming halt.
I'm not sure what you mean about the tracing_on question. The tracing_on file only connects to the tracing_on functionality in the kernel, which when clear will stop the ring buffers from recording data.
-- Steve
> > for (i = 0; i < tr->nr_topts; i++) { > > - /* > > - * Check if these flags have already been added. > > - * Some tracers share flags. > > - */ > > - if (tr->topts[i].tracer->flags == tracer->flags) > > + /* Make sure there's no duplicate flags. */ > > + if (WARN_ON_ONCE(tr->topts[i].tracer->flags == tracer->flags)) > > Thanks! It's really a safer way to throw out this warn if there is duplicate. > > > return; > > } > > > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > > index 8414fa40bf27..b4cae47f283e 100644 > > --- a/kernel/trace/trace.h > > +++ b/kernel/trace/trace.h > > @@ -345,6 +345,7 @@ struct tracer_opt { > > struct tracer_flags { > > u32 val; > > struct tracer_opt *opts; > > + struct tracer *trace; > > }; > > > > /* Makes more easy to define a tracer opt */ > > diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c > > index fcd41a166405..5a095c2e4b69 100644 > > --- a/kernel/trace/trace_functions.c > > +++ b/kernel/trace/trace_functions.c > > @@ -219,6 +219,8 @@ static void tracing_stop_function_trace(struct > > trace_array *tr) > > unregister_ftrace_function(tr->ops); > > } > > > > +static struct tracer function_trace; > > + > > static int > > func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set) > > { > > @@ -228,6 +230,10 @@ func_set_flag(struct trace_array *tr, u32 old_flags, u32 > > bit, int set) > > if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK)) > > break; > > > > + /* We can change this flag when not running. */ > > + if (tr->current_trace != &function_trace) > > + break; > > + > > At first I thought it should have some relation with the funcgraph trace. so i > guessed was wrong. Thx. > > > unregister_ftrace_function(tr->ops); > > > > if (set) { > > -- > > 1.8.3.1 > > > > >
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