linux-kernel - Re: [PATCH] tracing: use __this_cpu_read() in trace_buffered_event

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Date:   Thu, 17 Sep 2020 20:31:27 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Xianting Tian <tian.xianting@....com>
Cc:     <mingo@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: use __this_cpu_read() in
 trace_buffered_event_enable()

Sorry for the late reply (been busy with Linux Plumbers, took a
vacation, and then trying to catch up on all my email for the last two
months!)

But I just wanted to let you know that I added this to my queue.

Thanks!

-- Steve


On Thu, 13 Aug 2020 19:28:03 +0800
Xianting Tian <tian.xianting@....com> wrote:

> The code is executed with preemption disabled, so it's
> safe to use __this_cpu_read().
> 
> Signed-off-by: Xianting Tian <tian.xianting@....com>
> ---
>  kernel/trace/trace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index bb6226972..7d0d71ce9 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2514,7 +2514,7 @@ void trace_buffered_event_enable(void)
>  
>  		preempt_disable();
>  		if (cpu == smp_processor_id() &&
> -		    this_cpu_read(trace_buffered_event) !=
> +		    __this_cpu_read(trace_buffered_event) !=
>  		    per_cpu(trace_buffered_event, cpu))
>  			WARN_ON_ONCE(1);
>  		preempt_enable();