Messages in this thread | | | From | Mark-PK Tsai <> | Subject | Re: [PATCH v3 1/2] tracing: Avoid adding tracer option before update_tracer_options | Date | Tue, 26 Apr 2022 16:17:06 +0800 |
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> > To prepare for support asynchronous tracer_init_tracefs initcall, > > avoid calling create_trace_option_files before __update_tracer_options. > > Otherwise, create_trace_option_files will show warning because > > some tracers in trace_types list are already in tr->topts. > > > > For example, hwlat_tracer call register_tracer in late_initcall, > > and global_trace.dir is already created in tracing_init_dentry, > > hwlat_tracer will be put into tr->topts. > > Then if the __update_tracer_options is executed after hwlat_tracer > > registered, create_trace_option_files find that hwlat_tracer is > > already in tr->topts. > > > > 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> > > Before this patch: > > # ls /sys/kernel/tracing/options > annotate funcgraph-duration hex stacktrace > bin funcgraph-irqs irq-info sym-addr > blk_cgname funcgraph-overhead latency-format sym-offset > blk_cgroup funcgraph-overrun markers sym-userobj > blk_classic funcgraph-proc overwrite test_nop_accept > block funcgraph-tail pause-on-trace test_nop_refuse > context-info func-no-repeats printk-msg-only trace_printk > disable_on_free func_stack_trace print-parent userstacktrace > display-graph function-fork raw verbose > event-fork function-trace record-cmd > funcgraph-abstime graph-time record-tgid > funcgraph-cpu hash-ptr sleep-time > > > After this patch: > > # ls /sys/kernel/tracing/options > annotate disable_on_free irq-info raw trace_printk > bin display-graph latency-format record-cmd userstacktrace > blk_cgname event-fork markers record-tgid verbose > blk_cgroup function-fork overwrite stacktrace > blk_classic function-trace pause-on-trace sym-addr > block hash-ptr printk-msg-only sym-offset > context-info hex print-parent sym-userobj > > Not good.
Calling __update_tracer_options() when tracer_options_updated=false have no effect because it return directly in add_tracer_options(). I will fix it in v4 as you suggest in the below comment.
> > > --- > > kernel/trace/trace.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > index eb44418574f9..85ec758c4455 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); > > __update_tracer_options(tr); > > + tracer_options_updated = true; > > I think you want to set this before the __update, as doing it after just > makes the update a nop.
You are right. I will update in v4, thanks!
> > -- Steve > > > > mutex_unlock(&trace_types_lock); > > } > >
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