tracing: Avoid adding tracer option before update_tracer_options

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2155737

commit ef9188b
Author: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Date:   Tue Apr 26 20:24:06 2022 +0800

    tracing: Avoid adding tracer option before update_tracer_options

    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://lkml.kernel.org/r/20220426122407.17042-2-mark-pk.tsai@mediatek.com

    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>
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Signed-off-by: Thomas Huth <thuth@redhat.com>

Author: huth

kernel/trace/trace.c

@@ -6315,12 +6315,18 @@ 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);
 }
 
@@ -9144,6 +9150,7 @@ static void __update_tracer_options(struct trace_array *tr)
 static void update_tracer_options(struct trace_array *tr)
 {
 	mutex_lock(&trace_types_lock);
+	tracer_options_updated = true;
 	__update_tracer_options(tr);
 	mutex_unlock(&trace_types_lock);
 }