From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6E55EC3A59C for ; Fri, 16 Aug 2019 12:35:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DFD820644 for ; Fri, 16 Aug 2019 12:35:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727362AbfHPMfh (ORCPT ); Fri, 16 Aug 2019 08:35:37 -0400 Received: from ozlabs.org ([203.11.71.1]:35753 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726981AbfHPMfg (ORCPT ); Fri, 16 Aug 2019 08:35:36 -0400 Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4692pt0K9tz9sML; Fri, 16 Aug 2019 22:35:34 +1000 (AEST) From: Michael Ellerman To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] powerpc/futex: fix warning: 'oldval' may be used uninitialized in this function In-Reply-To: <86b72f0c134367b214910b27b9a6dd3321af93bb.1565774657.git.christophe.leroy@c-s.fr> References: <86b72f0c134367b214910b27b9a6dd3321af93bb.1565774657.git.christophe.leroy@c-s.fr> Date: Fri, 16 Aug 2019 22:35:31 +1000 Message-ID: <878srt70fg.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christophe Leroy writes: > CC kernel/futex.o > kernel/futex.c: In function 'do_futex': > kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized] > return oldval == cmparg; > ^ > kernel/futex.c:1651:6: note: 'oldval' was declared here > int oldval, ret; > ^ > > This is because arch_futex_atomic_op_inuser() only sets *oval > if ret is NUL and GCC doesn't see that it will use it only when I prefer 0 to "NUL", as ret is an int. I'll reword it. But otherwise this looks OK. cheers > ret is NUL. > > Anyway, the non-NUL ret path is an error path that won't suffer from > setting *oval, and as *oval is a local var in futex_atomic_op_inuser() > it will have no impact. > > Signed-off-by: Christophe Leroy > --- > arch/powerpc/include/asm/futex.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h > index 3a6aa57b9d90..eea28ca679db 100644 > --- a/arch/powerpc/include/asm/futex.h > +++ b/arch/powerpc/include/asm/futex.h > @@ -60,8 +60,7 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, > > pagefault_enable(); > > - if (!ret) > - *oval = oldval; > + *oval = oldval; > > prevent_write_to_user(uaddr, sizeof(*uaddr)); > return ret; > -- > 2.13.3