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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 9B2EFC43331 for ; Wed, 1 Apr 2020 22:01:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A41020719 for ; Wed, 1 Apr 2020 22:01:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=canb.auug.org.au header.i=@canb.auug.org.au header.b="qeMTYdMz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732428AbgDAWBD (ORCPT ); Wed, 1 Apr 2020 18:01:03 -0400 Received: from bilbo.ozlabs.org ([203.11.71.1]:56413 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732357AbgDAWBC (ORCPT ); Wed, 1 Apr 2020 18:01:02 -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 48t0WX17Mmz9sR4; Thu, 2 Apr 2020 09:00:56 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=canb.auug.org.au; s=201702; t=1585778459; bh=r5b2piY6/n72uqJFBNUFlpkDoMERU0WoLrX1VqgXSkQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qeMTYdMz0vIBNJyd5+3em9tWCEcQD0RhARuMLoCxU3Ib6sSaQLaSDSMSFflGLD54g UJoLZMIqokLiFWXBVsnJgQlqIuxcatpNwoaNR7fT+qDuhpyvWcKLKTVASxIPOwceJI sSY3ZdauN4YMNFnkWj34v32hcBuO3I+szSxmGLh2JjmHr444piTkl2UlvRYntMbY7F eKojTMrQ0tZesHuGNYR45AuVlopRj3SKqtfZYxm0lP6yuMQmZuLebGqyP+fe5Bmk1c PEtmGkr/MITwjU/hb0qmtJtqWuCu6RcvrKPacvU4rmozwoLwxcx/3R2zXeM/26GvWy gr7/r1VUudZ3w== Date: Thu, 2 Apr 2020 09:00:51 +1100 From: Stephen Rothwell To: Thomas Gleixner Cc: Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Linux Next Mailing List , Linux Kernel Mailing List , Al Viro Subject: Re: linux-next: build warning after merge of the tip tree Message-ID: <20200402090051.741905cd@canb.auug.org.au> In-Reply-To: <877dyzv6y2.fsf@nanos.tec.linutronix.de> References: <20200330134746.627dcd93@canb.auug.org.au> <20200401085753.617c1636@canb.auug.org.au> <877dyzv6y2.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="Sig_/T9rRW9/VqPZ6kK6l61A6RfB"; protocol="application/pgp-signature"; micalg=pgp-sha256 Sender: linux-next-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org --Sig_/T9rRW9/VqPZ6kK6l61A6RfB Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hi Thomas, On Wed, 01 Apr 2020 12:25:25 +0200 Thomas Gleixner wro= te: > > Stephen Rothwell writes: > > > > On Mon, 30 Mar 2020 13:47:46 +1100 Stephen Rothwell wrote: =20 > >> > >> After merging the tip tree, today's linux-next build (arm > >> multi_v7_defconfig) produced this warning: > >>=20 > >> kernel/futex.c: In function 'do_futex': > >> kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in= this function [-Wmaybe-uninitialized] > >> 1676 | return oldval =3D=3D cmparg; > >> | ~~~~~~~^~~~~~~~~ > >> kernel/futex.c:1652:6: note: 'oldval' was declared here > >> 1652 | int oldval, ret; > >> | ^~~~~~ > >>=20 > >> Introduced by commit > >>=20 > >> a08971e9488d ("futex: arch_futex_atomic_op_inuser() calling > >> conventions change") =20 >=20 > Huch? > =20 > >> but I don't arm-linux-gnueabi-gcc (Debian 9.2.1-21) 9.2.1 20191130see = how it makes this difference :-( =20 >=20 > Me neither. Which compiler version? arm-linux-gnueabi-gcc (Debian 9.2.1-21) 9.2.1 20191130 > I'm using arm-linux-gnueabi-gcc (Debian 8.3.0-2) 8.3.0 which does not > show that oddity. I assume it is because of the change to arch_futex_atomic_op_inuser() for arm and the compiler is not clever enough to work out that the early return from arch_futex_atomic_op_inuser() means that oldval is not referenced in its caller. --=20 Cheers, Stephen Rothwell --Sig_/T9rRW9/VqPZ6kK6l61A6RfB Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEENIC96giZ81tWdLgKAVBC80lX0GwFAl6FDxMACgkQAVBC80lX 0GwG+gf+KqrhLJkMSli8yzd+KnzQb3yhRcFWOx59V+ogiuf7SuvAa6/i+bIroF/c 9vS7QbDSom9B4KmUpTmUO2HG9Hr3w9F9lidZ1x3PwR23zIDOQasevQ7BvdjTNi05 KHWurUi8wpcrF8Szse8VnzznAwKzkpnzPbi8sJHVqfUMY+2BN6AmhY6yCZ/66YlD iSLzX9l+qkBeiEA7d+VMwRv4GHZTZ8lZyw+1bDotwJRE3YBrDNSpfcoolg2v/0xd U3bP2+6WMDOhFnWkyDtGGPNus3aCBipOuUHKNDeOuQK186j1jWVXQ08DyOVcOeT/ knRVY5Ku0NhkXHbl1/v3ppt9DOm5UQ== =suJO -----END PGP SIGNATURE----- --Sig_/T9rRW9/VqPZ6kK6l61A6RfB--