[for-next][PATCH 21/21] tracing: make tracer_init_tracefs initcall asynchronous

Steven Rostedt
2022-04-27T19:38:25Z

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

Move trace_eval_init() to subsys_initcall to make it start
earlier.
And to avoid tracer_init_tracefs being blocked by
trace_event_sem which trace_eval_init() hold [1],
queue tracer_init_tracefs() to eval_map_wq to let
the two works being executed sequentially.

It can speed up the initialization of kernel as result
of making tracer_init_tracefs asynchronous.

On my arm64 platform, it reduce ~20ms of 125ms which total
time do_initcalls spend.

Link: https://lkml.kernel.org/r/20220426122407.17042-3-mark-pk.tsai@mediatek.com

[1]: https://lore.kernel.org/r/68d7b3327052757d0cd6359a6c9015a85b437232.camel@pengutronix.de
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 32 ++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7275173c55d0..400d3e9fe9ff 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9615,6 +9615,7 @@ extern struct trace_eval_map *__stop_ftrace_eval_maps[];

static struct workqueue_struct *eval_map_wq __initdata;
static struct work_struct eval_map_work __initdata;
+static struct work_struct tracerfs_init_work __initdata;

static void __init eval_map_work_func(struct work_struct *work)
{
@@ -9640,6 +9641,8 @@ static int __init trace_eval_init(void)
return 0;
}

+subsys_initcall(trace_eval_init);
+
static int __init trace_eval_sync(void)
{
/* Make sure the eval map updates are finished */
@@ -9722,15 +9725,8 @@ static struct notifier_block trace_module_nb = {
};
#endif /* CONFIG_MODULES */

-static __init int tracer_init_tracefs(void)
+static __init void tracer_init_tracefs_work_func(struct work_struct *work)
{
- int ret;
-
- trace_access_lock_init();
-
- ret = tracing_init_dentry();
- if (ret)
- return 0;

event_trace_init();

@@ -9752,8 +9748,6 @@ static __init int tracer_init_tracefs(void)
trace_create_file("saved_tgids", TRACE_MODE_READ, NULL,
NULL, &tracing_saved_tgids_fops);

- trace_eval_init();
-
trace_create_eval_file(NULL);

#ifdef CONFIG_MODULES
@@ -9768,6 +9762,24 @@ static __init int tracer_init_tracefs(void)
create_trace_instances(NULL);

update_tracer_options(&global_trace);
+}
+
+static __init int tracer_init_tracefs(void)
+{
+ int ret;
+
+ trace_access_lock_init();
+
+ ret = tracing_init_dentry();
+ if (ret)
+ return 0;
+
+ if (eval_map_wq) {
+ INIT_WORK(&tracerfs_init_work, tracer_init_tracefs_work_func);
+ queue_work(eval_map_wq, &tracerfs_init_work);
+ } else {
+ tracer_init_tracefs_work_func(NULL);
+ }

return 0;
}
--
2.35.1