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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 D375BC433ED for ; Thu, 20 May 2021 12:21:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4C66F611C2 for ; Thu, 20 May 2021 12:21:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C66F611C2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8F6EB6B00C6; Thu, 20 May 2021 08:21:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 87FF56B00C7; Thu, 20 May 2021 08:21:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6F9726B00C8; Thu, 20 May 2021 08:21:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0164.hostedemail.com [216.40.44.164]) by kanga.kvack.org (Postfix) with ESMTP id 390076B00C6 for ; Thu, 20 May 2021 08:21:30 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C7F461812ED9E for ; Thu, 20 May 2021 12:21:29 +0000 (UTC) X-FDA: 78161519898.13.F88DE99 Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by imf08.hostedemail.com (Postfix) with ESMTP id 83A5C801911B for ; Thu, 20 May 2021 12:21:27 +0000 (UTC) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 14KCHI5W000535; Thu, 20 May 2021 07:17:18 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 14KCHAfi000527; Thu, 20 May 2021 07:17:10 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Thu, 20 May 2021 07:17:10 -0500 From: Segher Boessenkool To: Michael Ellerman Cc: "Aneesh Kumar K.V" , npiggin@gmail.com, linux-mm@kvack.org, kaleshsingh@google.com, joel@joelfernandes.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Guenter Roeck Subject: Re: [PATCH v5 5/9] powerpc/mm/book3s64: Update tlb flush routines to take a page walk cache flush argument Message-ID: <20210520121710.GR10366@gate.crashing.org> References: <20210422054323.150993-6-aneesh.kumar@linux.ibm.com> <20210515163525.GA1106462@roeck-us.net> <87pmxpqxb1.fsf@linux.ibm.com> <87a6ork1qp.fsf@mpe.ellerman.id.au> <20210519004514.GC10366@gate.crashing.org> <20210519120306.GD10366@gate.crashing.org> <87y2c9j1ov.fsf@mpe.ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87y2c9j1ov.fsf@mpe.ellerman.id.au> User-Agent: Mutt/1.4.2.3i X-Rspamd-Queue-Id: 83A5C801911B Authentication-Results: imf08.hostedemail.com; dkim=none; spf=pass (imf08.hostedemail.com: domain of segher@kernel.crashing.org designates 63.228.1.57 as permitted sender) smtp.mailfrom=segher@kernel.crashing.org; dmarc=none X-Rspamd-Server: rspam03 X-Stat-Signature: ga1a5fndw8dzq65r44pqfgx83dz6u5fz X-HE-Tag: 1621513287-833832 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi! On Thu, May 20, 2021 at 05:37:20PM +1000, Michael Ellerman wrote: > Segher Boessenkool writes: > > On Tue, May 18, 2021 at 07:45:14PM -0500, Segher Boessenkool wrote: > >> On Wed, May 19, 2021 at 10:26:22AM +1000, Michael Ellerman wrote: > >> > Guenter Roeck writes: > >> > > Ah, sorry. I wasn't aware that the following is valid C code > >> > > > >> > > void f1() > >> > > { > >> > > return f2(); > >> > > ^^^^^^ > >> > > } > >> > > > >> > > as long as f2() is void as well. Confusing, but we live and learn. > >> > > >> > It might be valid, but it's still bad IMHO. > >> > > >> > It's confusing to readers, and serves no useful purpose. > >> > >> And it actually explicitly is undefined behaviour in C90 already > >> (3.6.6.4 in C90, 6.8.6.4 in C99 and later). > > We use gnu89, which presumably does not make it UB. Indeed. That is kind of implied by the "as a GNU extension" below, but some explicit statement would be better, yup. > > ... but there is a GCC extension that allows this by default: > > > > For C only, warn about a 'return' statement with an expression in a > > function whose return type is 'void', unless the expression type is > > also 'void'. As a GNU extension, the latter case is accepted > > without a warning unless '-Wpedantic' is used. > > There's no chance we'll ever enable -Wpedantic, Good, because -pedantic adds a lot of much more annoying warnings as well. I find this extension questionable (like Guenter says it is confusing and has no purpose), so the only thing it is "good" for is it causes long email threads ;-) Other than those things it is harmless though. > so I guess it's allowed > for practical purposes. I guess clang must accept it too or we'd be > seeing warnings from it. Yup. Segher