----- Original Message ----- > From: "Steven Rostedt" <rost...@goodmis.org> > To: "Chunyu Hu" <ch...@redhat.com> > Cc: li...@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 <ch...@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 ;) > -- Steve > > From d39cdd2036a63eef17a14efbd969405ca5612886 Mon Sep 17 00:00:00 2001 > From: Chunyu Hu <ch...@redhat.com> > Date: Tue, 8 Mar 2016 21:37:01 +0800 > Subject: [PATCH] tracing: Make tracer_flags use the right set_flag callback > > When I was updating the ftrace_stress test of ltp. I encountered > a strange phenomemon, excute following steps: > > echo nop > /sys/kernel/debug/tracing/current_tracer > echo 0 > /sys/kernel/debug/tracing/options/funcgraph-cpu > bash: echo: write error: Invalid argument > > check dmesg: > [ 1024.903855] nop_test_refuse flag set to 0: we refuse.Now cat trace_options > to see the result > > The reason is that the trace option test will randomly setup trace > option under tracing/options no matter what the current_tracer is. > but the set_tracer_option is always using the set_flag callback > from the current_tracer. This patch adds a pointer to tracer_flags > and make it point to the tracer it belongs to. When the option is > setup, the set_flag of the right tracer will be used no matter > what the the current_tracer is. > > And the old dummy_tracer_flags is used for all the tracers which > doesn't have a tracer_flags, having issue to use it to save the > pointer of a tracer. So remove it and use dynamic dummy tracer_flags > for tracers needing a dummy tracer_flags, as a result, there are no > tracers sharing tracer_flags, so remove the check code. > > And save the current tracer to trace_option_dentry seems not good as > it may waste mem space when mount the debug/trace fs more than one time. > > Link: > http://lkml.kernel.org/r/1457444222-8654-1-git-send-email-ch...@redhat.com > > Signed-off-by: Chunyu Hu <ch...@redhat.com> > [ Fixed up function tracer options to work with the change ] > Signed-off-by: Steven Rostedt <rost...@goodmis.org> > --- > kernel/trace/trace.c | 28 ++++++++++++++-------------- > kernel/trace/trace.h | 1 + > kernel/trace/trace_functions.c | 6 ++++++ > 3 files changed, 21 insertions(+), 14 deletions(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index d9293402ee68..b401a1892dc6 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -74,11 +74,6 @@ static struct tracer_opt dummy_tracer_opt[] = { > { } > }; > > -static struct tracer_flags dummy_tracer_flags = { > - .val = 0, > - .opts = dummy_tracer_opt > -}; > - > static int > dummy_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set) > { > @@ -1258,12 +1253,20 @@ int __init register_tracer(struct tracer *type) > > if (!type->set_flag) > type->set_flag = &dummy_set_flag; > - if (!type->flags) > - type->flags = &dummy_tracer_flags; > - else > + if (!type->flags) { > + /*allocate a dummy tracer_flags*/ > + type->flags = kmalloc(sizeof(*type->flags), GFP_KERNEL); > + if (!type->flags) > + return -ENOMEM; > + type->flags->val = 0; > + type->flags->opts = dummy_tracer_opt; > + } else > if (!type->flags->opts) > type->flags->opts = dummy_tracer_opt; > > + /* store the tracer for __set_tracer_option */ > + type->flags->trace = type; > + > ret = run_tracer_selftest(type); > if (ret < 0) > goto out; > @@ -3505,7 +3508,7 @@ static int __set_tracer_option(struct trace_array *tr, > struct tracer_flags *tracer_flags, > struct tracer_opt *opts, int neg) > { > - struct tracer *trace = tr->current_trace; > + struct tracer *trace = tracer_flags->trace; > int ret; > > ret = trace->set_flag(tr, tracer_flags->val, opts->bit, !neg); > @@ -6391,11 +6394,8 @@ create_trace_option_files(struct trace_array *tr, > struct tracer *tracer) > return; > > 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 > > -- Regards, Chunyu Hu
