Re: [PATCH] ftrace: Use this_cpu_ptr() instead of per_cpu_ptr(smp_processor_id())

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 19 Aug 2024 14:01:53 +0800
Li Chen <me@linux.beauty> wrote:

> From: Li Chen <chenl311@chinatelecom.cn>
> 
> Use this_cpu_ptr() instead of open coding the equivalent in various
> ftrace functions.

Thanks.

This code was written (2009) before this_cpu_ptr() was introduced (2010).

-- Steve

> 
> Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
> ---
>  kernel/trace/trace_functions.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
> index 3b0cea37e0297..65fed0bbc5c22 100644
> --- a/kernel/trace/trace_functions.c
> +++ b/kernel/trace/trace_functions.c
> @@ -184,7 +184,6 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
>  	struct trace_array_cpu *data;
>  	unsigned int trace_ctx;
>  	int bit;
> -	int cpu;
>  
>  	if (unlikely(!tr->function_enabled))
>  		return;
> @@ -195,8 +194,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
>  
>  	trace_ctx = tracing_gen_ctx();
>  
> -	cpu = smp_processor_id();
> -	data = per_cpu_ptr(tr->array_buffer.data, cpu);
> +	data = this_cpu_ptr(tr->array_buffer.data);
>  	if (!atomic_read(&data->disabled))
>  		trace_function(tr, ip, parent_ip, trace_ctx);
>  
> @@ -300,7 +298,6 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>  	unsigned int trace_ctx;
>  	unsigned long flags;
>  	int bit;
> -	int cpu;
>  
>  	if (unlikely(!tr->function_enabled))
>  		return;
> @@ -309,8 +306,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>  	if (bit < 0)
>  		return;
>  
> -	cpu = smp_processor_id();
> -	data = per_cpu_ptr(tr->array_buffer.data, cpu);
> +	data = this_cpu_ptr(tr->array_buffer.data);
>  	if (atomic_read(&data->disabled))
>  		goto out;
>  
> @@ -321,7 +317,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
>  	 * TODO: think about a solution that is better than just hoping to be
>  	 * lucky.
>  	 */
> -	last_info = per_cpu_ptr(tr->last_func_repeats, cpu);
> +	last_info = this_cpu_ptr(tr->last_func_repeats);
>  	if (is_repeat_check(tr, last_info, ip, parent_ip))
>  		goto out;
>