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Subject[PATCH v3 1/2] tracing: Avoid adding tracer option before update_tracer_options
Date
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>
---
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;
mutex_unlock(&trace_types_lock);
}

--
2.18.0
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