linux-kernel - Re: [PATCH] tracer: hwlat: allow to be default bootup tracer

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Date:   Wed, 16 Aug 2017 10:28:03 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Pratyush Anand <panand@...hat.com>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracer: hwlat: allow to be default bootup tracer

On Fri, 11 Aug 2017 17:01:21 +0530
Pratyush Anand <panand@...hat.com> wrote:

> hwlat is not a production kernel tracer, however it can be used to
> identify any HW latency issue during kernel boot as well.Therefore call
> init_hwlat_tracer() though core_initcall() so that we can pass
> ftrace=hwlat in kernel commandline parameter and we can have hwlat as
> default bootup tracer.
> 
> Signed-off-by: Pratyush Anand <panand@...hat.com>
> ---
>  kernel/trace/trace_hwlat.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> index d7c8e4ec3d9d..09f8f0950b6c 100644
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -630,4 +630,4 @@ __init static int init_hwlat_tracer(void)
>  
>  	return 0;
>  }
> -late_initcall(init_hwlat_tracer);
> +core_initcall(init_hwlat_tracer);

No that is not the right fix. hwlat tracer should not be called by core
init.

I already have a fix in linux-next. I'm doing some more code that needs
testing before I send it to Linus.

-- Steve