The init_blk_tracer() function causes significant boot delay as it
waits for the trace_event_sem lock held by trace_event_update_all().
Specifically, its child function register_trace_event() requires
this lock, which is occupied for an extended period during boot.

To resolve this, when the trace_async_init parameter is enabled, the
execution of primary init_blk_tracer() is moved to the trace_init_wq
workqueue, allowing it to run asynchronously. and prevent blocking
the main boot thread.

Signed-off-by: Yaxiong Tian <redacted>
---
 kernel/trace/blktrace.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index d031c8d80be4..56c7270ec447 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c

@@ -1832,7 +1832,9 @@ static struct trace_event trace_blk_event = {
 	.funcs		= &trace_blk_event_funcs,
 };
 
-static int __init init_blk_tracer(void)
+static struct work_struct blktrace_works __initdata;
+
+static int __init __init_blk_tracer(void)
 {
 	if (!register_trace_event(&trace_blk_event)) {
 		pr_warn("Warning: could not register block events\n");

@@ -1852,6 +1854,25 @@ static int __init init_blk_tracer(void)
 	return 0;
 }
 
+static void __init blktrace_works_func(struct work_struct *work)
+{
+	__init_blk_tracer();
+}
+
+static int __init init_blk_tracer(void)
+{
+	int ret = 0;
+
+	if (trace_init_wq && trace_async_init) {
+		INIT_WORK(&blktrace_works, blktrace_works_func);
+		queue_work(trace_init_wq, &blktrace_works);
+	} else {
+		ret = __init_blk_tracer();
+	}
+
+	return ret;
+}
+
 device_initcall(init_blk_tracer);
 
 static int blk_trace_remove_queue(struct request_queue *q)