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

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Message-Id: <20220119041737.1805441-1-ytcoode@gmail.com>
Date:   Wed, 19 Jan 2022 04:17:37 +0000
From:   Yuntao Wang <ytcoode@...il.com>
To:     Lukas Bulwahn <lukas.bulwahn@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Yuntao Wang <ytcoode@...il.com>
Subject: Re: [PATCH] tracing: Remove redundant assignment to variable ret

On Mon, Jan 17, 2022 at 3:47 PM Lukas Bulwahn <lukas.bulwahn@...il.com> wrote:
> Dear Yuntao,
>
>
> when you consider removing dead-store assignments guided by some static
> analyzer, you need to check if the code you are looking at is actually
> missing an error-handling branch.
>
> In this case, ftrace_process_locs() may return -ENOMEM, and the caller
> needs to appropriately deal with this error return code. Your patch
> does not change the code at all, i.e., the compiled object code is the
> same as after the patch as before.
>
> Think about how to deal appropriately with the -ENOMEM return in this
> caller and submit a patch that implements the right error-handling
> branch or argue in your commit message why that is not needed at all.
>
> If you do not understand or cannot check such basic code properties for
> dead-store assignments, it might be better to work on some other aspect
> and area of the kernel repository. E.g., the kernel documentation build
> also has a few warnings that deserve patches to be fixed.
>
>
> Best regards,
>
> Lukas

Dear Lukas,

Thanks for your reply.

Actually, I had read the source code carefully and noticed the possible
error return code -ENOMEM of the ftrace_process_locs() function.

At first I was going to implement an error-handling branch as you said,
but after digging into more details, I discovered:

- The ftrace_init() function did not handle the error return code of the ftrace_process_locs() function since the first version.
- The ftrace_module_init() function did not handle it either.

To keep consistent with the existing code, I just removed the assignment
in that patch.

Maybe we should deal with the error return code more appropriately,
at least print some warnings?

Best regards,

Yuntao