linux-kernel - Re: [PATCH v2 1/3] tracing: Rename `eval_map_wq` and export it for asynchronous use by other modules

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Message-ID: <20260126093646.3922b905@gandalf.local.home>
Date: Mon, 26 Jan 2026 09:36:46 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Yaxiong Tian <tianyaxiong@...inos.cn>
Cc: axboe@...nel.dk, mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] tracing: Rename `eval_map_wq` and export it for
 asynchronous use by other modules

On Mon, 26 Jan 2026 10:43:16 +0800
Yaxiong Tian <tianyaxiong@...inos.cn> wrote:

Hi,

Some of your terminology is a little confusing. The subject says "modules"
but no module will use it (the term module means loadable code at runtime
into the Linux kernel). A better subject would be:


  tracing: Rename `eval_map_wq` and allow other parts of tracing use it


> The eval_map_work_func() function, though queued in eval_map_wq,
> holds the trace_event_sem read-write lock for a long time during
> kernel boot. This causes blocking issues for other functions.
> 
> Rename eval_map_wq to trace_init_wq and export it, thereby allowing

Also saying "export" for a function means something like "EXPORT_SYMBOLE()"
which again deals with Linux modules. A better term is "make it global".

> other modules to schedule work on this queue asynchronously and

 .. other parts of tracing ..

> avoiding blockage of the main boot thread.
> 
> Signed-off-by: Yaxiong Tian <tianyaxiong@...inos.cn>

Other than that, this patch looks good.

-- Steve

> ---
>  kernel/trace/trace.c | 18 +++++++++---------
>  kernel/trace/trace.h |  2 ++
>  2 files changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index e18005807395..c61e30cb7339 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -10774,7 +10774,7 @@ int tracing_init_dentry(void)
>  extern struct trace_eval_map *__start_ftrace_eval_maps[];
>  extern struct trace_eval_map *__stop_ftrace_eval_maps[];
>  
> -static struct workqueue_struct *eval_map_wq __initdata;
> +struct workqueue_struct *trace_init_wq __initdata;
>  static struct work_struct eval_map_work __initdata;
>  static struct work_struct tracerfs_init_work __initdata;
>  
> @@ -10790,15 +10790,15 @@ static int __init trace_eval_init(void)
>  {
>  	INIT_WORK(&eval_map_work, eval_map_work_func);
>  
> -	eval_map_wq = alloc_workqueue("eval_map_wq", WQ_UNBOUND, 0);
> -	if (!eval_map_wq) {
> -		pr_err("Unable to allocate eval_map_wq\n");
> +	trace_init_wq = alloc_workqueue("trace_init_wq", WQ_UNBOUND, 0);
> +	if (!trace_init_wq) {
> +		pr_err("Unable to allocate trace_init_wq\n");
>  		/* Do work here */
>  		eval_map_work_func(&eval_map_work);
>  		return -ENOMEM;
>  	}
>  
> -	queue_work(eval_map_wq, &eval_map_work);
> +	queue_work(trace_init_wq, &eval_map_work);
>  	return 0;
>  }
>  
> @@ -10807,8 +10807,8 @@ subsys_initcall(trace_eval_init);
>  static int __init trace_eval_sync(void)
>  {
>  	/* Make sure the eval map updates are finished */
> -	if (eval_map_wq)
> -		destroy_workqueue(eval_map_wq);
> +	if (trace_init_wq)
> +		destroy_workqueue(trace_init_wq);
>  	return 0;
>  }
>  
> @@ -10969,9 +10969,9 @@ static __init int tracer_init_tracefs(void)
>  	if (ret)
>  		return 0;
>  
> -	if (eval_map_wq) {
> +	if (trace_init_wq) {
>  		INIT_WORK(&tracerfs_init_work, tracer_init_tracefs_work_func);
> -		queue_work(eval_map_wq, &tracerfs_init_work);
> +		queue_work(trace_init_wq, &tracerfs_init_work);
>  	} else {
>  		tracer_init_tracefs_work_func(NULL);
>  	}
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index de4e6713b84e..e52f259f8945 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -770,6 +770,8 @@ extern unsigned long nsecs_to_usecs(unsigned long nsecs);
>  
>  extern unsigned long tracing_thresh;
>  
> +extern struct workqueue_struct *trace_init_wq __initdata;
> +
>  /* PID filtering */
>  
>  bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,