linux-kernel - Re: [RFC] trace_irqsoff: remove redundant reset per-CPU buff

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Message-ID: <20160204214045.1d6c2893@grimm.local.home>
Date:	Thu, 4 Feb 2016 21:40:45 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dmitry Safonov <0x7f454c46@...il.com>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org, rostedt@...dmis.org
Subject: Re: [RFC] trace_irqsoff: remove redundant reset per-CPU buff

On Mon, 19 Oct 2015 21:10:26 +0300
Dmitry Safonov <0x7f454c46@...il.com> wrote:

>   There is no reason to do it twice: from commit b6f11df26fdc28
> ("trace: Call tracing_reset_online_cpus before tracer->init()")
> resetting of per-CPU buffers done before tracer->init() call.
> 
> tracer->init() calls {irqs,preempt,preemptirqs}off_tracer_init() and it
> calls __irqsoff_tracer_init(), which resets per-CPU ringbuffer second
> time.
> It's slowpath, but anyway.

Bah, I said I'd look at this and I did. But never added it to my queue.
It's not a big deal as this is the slow path but it makes sense. I knew
there was a patch from you to get but saw the TP_ARGS redefining patch
and thought that was it.

I Cc'd myself on this to make sure I see it again.

-- Steve

> 
> Signed-off-by: Dmitry Safonov <0x7f454c46@...il.com>
> ---
>  kernel/trace/trace_irqsoff.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
> index 8523ea345f2b1a..4ebcb8bfaced24 100644
> --- a/kernel/trace/trace_irqsoff.c
> +++ b/kernel/trace/trace_irqsoff.c
> @@ -612,7 +612,6 @@ static int __irqsoff_tracer_init(struct trace_array *tr)
>  	irqsoff_trace = tr;
>  	/* make sure that the tracer is visible */
>  	smp_wmb();
> -	tracing_reset_online_cpus(&tr->trace_buffer);
>  
>  	ftrace_init_array_ops(tr, irqsoff_tracer_call);
>