Messages in this thread | | | Date | Wed, 23 Mar 2022 09:30:21 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] tracing: Avoid adding duplicated tracer options when update_tracer_options is running in parallel |
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On Wed, 23 Mar 2022 11:24:42 +0800 Mark-PK Tsai <mark-pk.tsai@mediatek.com> wrote:
> When update_tracer_options is running in parallel, > tr->tops might be updated before the trace_types list traversal. > Let update_tracer_options traverse the trace_types list safely in > kernel init time and avoid the tr->tops update before it finish.
??? Have you seen a bug here? I'm totally confused by this.
> > Link: https://lore.kernel.org/lkml/20220322133339.GA32582@xsang-OptiPlex-9020/ > Reported-by: kernel test robot <oliver.sang@intel.com> > Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com> > --- > kernel/trace/trace.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index adb37e437a05..2974ae056068 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -6317,12 +6317,18 @@ static void tracing_set_nop(struct trace_array *tr) > tr->current_trace = &nop_trace; > } > > +static bool tracer_options_updated; > + > static void add_tracer_options(struct trace_array *tr, struct tracer *t) > { > /* Only enable if the directory has been created already. */ > if (!tr->dir) > return; > > + /* Only create trace option files after update_tracer_options finish */ > + if (!tracer_options_updated) > + return; > + > create_trace_option_files(tr, t); > } > > @@ -9133,6 +9139,7 @@ static void update_tracer_options(struct trace_array *tr) > { > mutex_lock(&trace_types_lock);
How is update_trace_options run in parallel?
There's a mutex that protects it.
-- Steve
> __update_tracer_options(tr); > + tracer_options_updated = true; > mutex_unlock(&trace_types_lock); > } >
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