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=-9.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 7AB4BC43387 for ; Wed, 16 Jan 2019 08:47:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4770920840 for ; Wed, 16 Jan 2019 08:47:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547628425; bh=ENq0LuKgcRn0ltfMIgMJAq2XqV1ELqCxTiQfipMOs1w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=RLV8VLnmxI9UxEJFOu5bxZ1gTYsB681NWvGWnv+bSzAjbk8LU0q2ImFQvEDz6yJ/o JTKY+NNjz34gOftVA2A8K17/TiVF2d20lReeu05VVtfLnMtCTZ2vs58T+eFiUdB5A7 IGsufGWWDAt1iJ1M8TCdgHKVwhxMehX1jymiOqWM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390021AbfAPIrD (ORCPT ); Wed, 16 Jan 2019 03:47:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:36998 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388910AbfAPIrD (ORCPT ); Wed, 16 Jan 2019 03:47:03 -0500 Received: from localhost (unknown [95.99.207.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9559D20840; Wed, 16 Jan 2019 08:47:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1547628422; bh=ENq0LuKgcRn0ltfMIgMJAq2XqV1ELqCxTiQfipMOs1w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kiH949EI8DXx+LxAH5AGCqjuTlKsu+DgU5EzysJUJu5vG0QRD2/M9++Tz1AZ28T7V 1qqo8Ped3h1FpJXpXT5+gPGETCKiMgU5gprp2zRXqx3HpvA9usj8rOhIDOMUVEifhW 6qTTTXGs7AUe6KfAYUSXbNof44BOW22wBT0rQq20= Date: Wed, 16 Jan 2019 09:46:58 +0100 From: Greg Kroah-Hartman To: Nathan Chancellor Cc: devel@driverdev.osuosl.org, Nick Desaulniers , linux-kernel@vger.kernel.org Subject: Re: [PATCH] staging: rtl8723bs: Fix build error with Clang when inlining is disabled Message-ID: <20190116084658.GA28112@kroah.com> References: <20190116060302.8882-1-natechancellor@gmail.com> <20190116064202.GA25498@kroah.com> <20190116065340.GA5336@flashbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190116065340.GA5336@flashbox> User-Agent: Mutt/1.11.2 (2019-01-07) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 15, 2019 at 11:53:40PM -0700, Nathan Chancellor wrote: > On Wed, Jan 16, 2019 at 07:42:02AM +0100, Greg Kroah-Hartman wrote: > > On Tue, Jan 15, 2019 at 11:03:02PM -0700, Nathan Chancellor wrote: > > > When CONFIG_NO_AUTO_INLINE was present in linux-next (which added > > > '-fno-inline-functions' to KBUILD_CFLAGS), an allyesconfig build with > > > Clang failed at the modpost stage: > > > > > > ERROR: "is_broadcast_mac_addr" [drivers/staging/rtl8723bs/r8723bs.ko] undefined! > > > ERROR: "is_zero_mac_addr" [drivers/staging/rtl8723bs/r8723bs.ko] undefined! > > > ERROR: "is_multicast_mac_addr" [drivers/staging/rtl8723bs/r8723bs.ko] undefined! > > > > > > These functions were marked as extern inline, meaning that if inlining > > > doesn't happen, the function will be undefined, as it is above. > > > > > > This happens to work with GCC because the '-fno-inline-functions' option > > > respects the __inline attribute so all instances of these functions are > > > inlined as expected and the definition doesn't actually matter. However, > > > with Clang and '-fno-inline-functions', a function has to be marked with > > > the __always_inline attribute to be considered for inlining, which none > > > of these functions are. Clang tries to find the symbol definition > > > elsewhere as it was told and fails, which trickles down to modpost. > > > > > > To make sure that this code compiles regardless of compiler and make the > > > intention of the code clearer, use 'static __always_inline' to ensure > > > that these functions are always inlined. Some alternative solutions > > > included 'extern __always_inline' or converting these functions to > > > macros (so the preprocessor deals with them) but I would argue this is > > > the more "standard" solution. > > > > > > Signed-off-by: Nathan Chancellor > > > --- > > > drivers/staging/rtl8723bs/include/ieee80211.h | 6 +++--- > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > diff --git a/drivers/staging/rtl8723bs/include/ieee80211.h b/drivers/staging/rtl8723bs/include/ieee80211.h > > > index bcc8dfa8e672..959e822315b5 100644 > > > --- a/drivers/staging/rtl8723bs/include/ieee80211.h > > > +++ b/drivers/staging/rtl8723bs/include/ieee80211.h > > > @@ -850,18 +850,18 @@ enum ieee80211_state { > > > #define IP_FMT "%pI4" > > > #define IP_ARG(x) (x) > > > > > > -extern __inline int is_multicast_mac_addr(const u8 *addr) > > > +static __always_inline int is_multicast_mac_addr(const u8 *addr) > > > > Ick, really? This is in a .h file, the .c file sees this, so why isn't > > clang picking it up? Worst case it just makes it a "normal" function > > and doesn't inline it, right? > > > > As I understand it, the meaning of 'extern inline' is basically use this > defintion when inlining, otherwise use one from a different file or > translation unit. See commit d0a8d9378d16 ("x86/paravirt: Make > native_save_fl() extern inline"). These functions don't have any other > declaration/definition so when they aren't inlined, they don't exist. > > > How about just replacing "extern" with "static", that should solve this, > > adding "__always_inline" everywhere is not going to be fun and doesn't > > make any sense. > > > > Yes, that would work (and what I originally tested). My assumption with > the code is that it was intended for this function to always be inlined > but if you'd rather it just be 'static', I am happy to send a v2! This code is not trying to be that smart, someone just put the extern in there without realizing it. So making it static is the correct fix, so a v2 would be great. Odds are, almost all other places in the kernel that you hit with this also needs the same fixup, no need to be fancy here :) thanks, greg k-h