linux-kernel - Re: [PATCH] percpu: initialize best

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Message-ID: <CAEcHRTr5TSEPX8Pigbx2O4n8rA8gO0JosDZvX9dhRh4fhi7-ig@mail.gmail.com>
Date:   Mon, 17 May 2021 08:45:09 +0900
From:   Wonhyuk Yang <vvghjk1234@...il.com>
To:     trix@...hat.com
Cc:     Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] percpu: initialize best_upa variable

On Sun, May 16, 2021 at 3:08 AM <trix@...hat.com> wrote:

> Static analysis reports this problem
> percpu.c:2945:6: warning: Assigned value is garbage or undefined
>         upa = best_upa;
>             ^ ~~~~~~~~
> best_upa may not be set, so initialize it.

Hi,

Actually, best_upa is always set in the for loop below. when upa is 1,
It will always satisfy all conditions.

> diff --git a/mm/percpu.c b/mm/percpu.c
> index a257c3efdf18b..6578b706fae81 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -2916,6 +2916,7 @@ static struct pcpu_alloc_info * __init __flatten pcpu_build_alloc_info(
>          * Related to atom_size, which could be much larger than the unit_size.
>          */
>         last_allocs = INT_MAX;
> +       best_upa = max_upa;
>         for (upa = max_upa; upa; upa--) {
>                 int allocs = 0, wasted = 0;

It doesn't seem to be a problem. But, how about this?

best_upa = 1;
for (upa = max_upa; upa>1; upa--)