[PATCH 5.4 339/411] tracing: Avoid adding tracer option before update_tracer_options

Greg Kroah-Hartman
2022-06-13T11:40:59Z

From: Mark-PK Tsai <mark-pk.tsai@mediatek.com>

[ Upstream commit ef9188bcc6ca1d8a2ad83e826b548e6820721061 ]

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: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ce9165de019c..55da88f18342 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5638,12 +5638,18 @@ 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);
}

@@ -8391,6 +8397,7 @@ 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);
}
--
2.35.1