linux-kernel - Re: [PATCH] tracing: Remove redundant assignment to event

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Message-ID: <20210507091625.0bcccf43@gandalf.local.home>
Date:   Fri, 7 May 2021 09:16:25 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Remove redundant assignment to event_var

On Fri,  7 May 2021 18:23:50 +0800
Jiapeng Chong <jiapeng.chong@...ux.alibaba.com> wrote:

> Variable event_var is set to 'ERR_PTR(-EINVAL)', but this value
> is never read as it is overwritten or not used later on, hence
> it is a redundant assignment and can be removed.
> 
> Clean up the following clang-analyzer warning:
> 
> kernel/trace/trace_events_hist.c:2437:21: warning: Value stored to
> 'event_var' during its initialization is never read
> [clang-analyzer-deadcode.DeadStores].
> 
> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> ---
>  kernel/trace/trace_events_hist.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index c1abd63..b37342c 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -2434,7 +2434,7 @@ static struct trace_event_file *event_file(struct trace_array *tr,
>  		      char *subsys_name, char *event_name, char *field_name)
>  {
>  	struct trace_array *tr = target_hist_data->event_file->tr;
> -	struct hist_field *event_var = ERR_PTR(-EINVAL);
> +	struct hist_field *event_var;
>  	struct hist_trigger_data *hist_data;
>  	unsigned int i, n, first = true;
>  	struct field_var_hist *var_hist;

Thanks, but if you are going to make this change, please move the
declaration of event_var below (or above) key_field, as their names are
both the same size in length and are of the same type. This keeps the
"upside-down x-mas tree" look of the declarations.

-- Steve