Re: [PATCH] tracing: Use kstrdup_const() for constant hist field type

[Masami Hiramatsu (Google) <mhiramat@kernel.org>]

On Tue, 26 May 2026 17:51:05 +0800
Yu Peng <pengyu@kylinos.cn> wrote:

> The HIST_FIELD_FL_CONST path duplicates the literal "u64" type with
> kstrdup(), then releases it through kfree_const().
> 
> Use kstrdup_const() instead, avoiding the allocation for a .rodata string
> while keeping the matching free helper.
> 

Since we are using kfree_const() to free hist_field->type,
we can just point it as same as HIST_FIELD_FL_HITCOUNT case.

Thanks,

> Signed-off-by: Yu Peng <pengyu@kylinos.cn>
> ---
>  kernel/trace/trace_events_hist.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index eb2c2bc8bc3d..6ffe9f4720a0 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -1992,7 +1992,7 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
>  	if (flags & HIST_FIELD_FL_CONST) {
>  		hist_field->fn_num = HIST_FIELD_FN_CONST;
>  		hist_field->size = sizeof(u64);
> -		hist_field->type = kstrdup("u64", GFP_KERNEL);
> +		hist_field->type = kstrdup_const("u64", GFP_KERNEL);
>  		if (!hist_field->type)
>  			goto free;
>  		goto out;
> -- 
> 2.43.0


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>