linux-kernel - Re: [PATCH v4 5/5] blktrace: Make init_blk_tracer() asynchronous when trace_async

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Message-ID: <20260128194104.30051be1@gandalf.local.home>
Date: Wed, 28 Jan 2026 19:41:04 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Yaxiong Tian <tianyaxiong@...inos.cn>, axboe@...nel.dk
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com, corbet@....net,
 skhan@...uxfoundation.org, linux-trace-kernel@...r.kernel.org,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH v4 5/5] blktrace: Make init_blk_tracer() asynchronous
 when trace_async_init set


Jens,

Can you give me an acked-by on this patch and I can take the series through
my tree.

Or perhaps this doesn't even need to test the trace_async_init flag and can
always do the work queue? Does blk_trace ever do tracing at boot up? That
is, before user space starts?

Thanks,

-- Steve


On Wed, 28 Jan 2026 20:55:54 +0800
Yaxiong Tian <tianyaxiong@...inos.cn> wrote:

> 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 <tianyaxiong@...inos.cn>
> ---
>  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)