blktrace: Make init_blk_tracer() asynchronous

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, 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.

Link: https://patch.msgid.link/20260204015353.163331-1-tianyaxiong@kylinos.cn
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index d031c8d80be4fdc2589b3dd8d6f633805ac8d584..d611cd1f02ef815877680de32e4685549c26cb36 100644 (file)
--- 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) {
+               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)