linux-kernel - Re: [PATCH] fgraph: fix unused value in register_ftrace

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Message-ID: <20241022025637.6852bac9@rorschach.local.home>
Date: Tue, 22 Oct 2024 02:56:37 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Gianfranco Trad <gianf.trad@...il.com>
Cc: mhiramat@...nel.org, mark.rutland@....com,
 mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, skhan@...uxfoundation.org
Subject: Re: [PATCH] fgraph: fix unused value in register_ftrace_graph()

On Mon, 21 Oct 2024 12:24:29 +0200
Gianfranco Trad <gianf.trad@...il.com> wrote:

> Coverity reports unused assignment to value ret. [1]
> ret is assigned to 0 here, but that stored value is overwritten before
> it can be used. The overwrite might happen either at line 1277, 1290 
> or eventually at line 1306. Therefore, cleanup the unused assignment.
> 
> [1] Coverity Scan, CID 1633338

What does the above mean? For such a simple change, is it really
unnecessary?

> 
> Signed-off-by: Gianfranco Trad <gianf.trad@...il.com>
> ---
>  kernel/trace/fgraph.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> index 41e7a15dcb50..cc2e065c1c8d 100644
> --- a/kernel/trace/fgraph.c
> +++ b/kernel/trace/fgraph.c
> @@ -1262,7 +1262,6 @@ int register_ftrace_graph(struct fgraph_ops *gops)
>  			return ret;
>  		}
>  		fgraph_initialized = true;
> -		ret = 0;

Not to mention that if this is to go, why not get rid of the
declaration part too? That is:

-	int ret = 0;
+	int ret;

But still, this code is about to be merged with other code where this
change may cause issues. This is such a slow path that getting rid of
the extra initialization may not be worth it.

-- Steve


>  	}
>  
>  	if (!fgraph_array[0]) {