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From:   Tianxianting <tian.xianting@h3c.com>
To:     Steven Rostedt <rostedt@goodmis.org>
CC:     "mingo@redhat.com" <mingo@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] tracing: use __this_cpu_read() in
 trace_buffered_event_enable()
Thread-Topic: [PATCH] tracing: use __this_cpu_read() in
 trace_buffered_event_enable()
Thread-Index: AQHWcWW/lUMuTErgSEmeCDizYMhoyqltPS+AgACT0gA=
Date:   Fri, 18 Sep 2020 01:21:37 +0000
Message-ID: <87803c1d960c4b17b59eb39346fdb028@h3c.com>
References: <20200813112803.12256-1-tian.xianting@h3c.com>
 <20200917203127.091e23f2@rorschach.local.home>
In-Reply-To: <20200917203127.091e23f2@rorschach.local.home>
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Hi Steven,
Thanks for your reply:)

-----Original Message-----
From: Steven Rostedt [mailto:rostedt@goodmis.org] 
Sent: Friday, September 18, 2020 8:31 AM
To: tianxianting (RD) <tian.xianting@h3c.com>
Cc: mingo@redhat.com; linux-kernel@vger.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@h3c.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@h3c.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();