linux-kernel - Re: [PATCH tip/core/rcu 9/9] rcu: Suppress levelspread uninitialized messages

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Date:   Thu, 3 Oct 2019 10:53:03 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     paulmck@...nel.org
Cc:     rcu@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Lai Jiangshan <jiangshanlai@...il.com>, dipankar@...ibm.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Triplett <josh@...htriplett.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        David Howells <dhowells@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH tip/core/rcu 9/9] rcu: Suppress levelspread uninitialized messages

Hi Paul,

On Thu, Oct 3, 2019 at 3:49 AM <paulmck@...nel.org> wrote:
> From: "Paul E. McKenney" <paulmck@...nel.org>
>
> New tools bring new warnings, and with v5.3 comes:

According to the kisskb build logs, it happens with gcc 4.6.3 only ;-)

> kernel/rcu/srcutree.c: warning: 'levelspread[<U aa0>]' may be used uninitialized in this function [-Wuninitialized]:  => 121:34
>
> This commit suppresses this warning by initializing the full array
> to INT_MIN, which will result in failures should any out-of-bounds
> references appear.
>
> Reported-by: Michael Ellerman <mpe@...erman.id.au>
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
(for the initialization loop, not for the actual INT_MIN value)

Unfortunately I don't have a gcc-4.6.3 Linux cross-compiler anymore.
I tried with msp430-gcc-4.6.3 and some hackery to get it to compile,
but that didn't let me reproduce the warning.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds