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=-6.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,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 80F63C433E0 for ; Wed, 6 Jan 2021 20:42:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 015EF23136 for ; Wed, 6 Jan 2021 20:42:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 015EF23136 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 35F2F8D010C; Wed, 6 Jan 2021 15:42:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 30EBC8D0090; Wed, 6 Jan 2021 15:42:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1D8558D010C; Wed, 6 Jan 2021 15:42:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0155.hostedemail.com [216.40.44.155]) by kanga.kvack.org (Postfix) with ESMTP id 0738C8D0090 for ; Wed, 6 Jan 2021 15:42:26 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id C864B181AEF2A for ; Wed, 6 Jan 2021 20:42:25 +0000 (UTC) X-FDA: 77676523050.24.sleep06_0207187274e4 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id B01C61A4A5 for ; Wed, 6 Jan 2021 20:42:25 +0000 (UTC) X-HE-Tag: sleep06_0207187274e4 X-Filterd-Recvd-Size: 2315 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Wed, 6 Jan 2021 20:42:25 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id B71A62311B; Wed, 6 Jan 2021 20:42:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1609965744; bh=B+PNb+h2TeheRTPPGBzTfoOQ6M+qd4Q24FS81ZUfhlI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=KV/Ds+kDNkjHOEmMFYGyLDU52yYBs5Yt7qulmBQChv/DsKJiOzNZqULO+dOgLL4Gp 9AoDKCTZ8oaf0ZBZBVlYT9e2jSeghaJxiU5WVA71n+/ATEWZ/VKScY59UDSlYSL8JU mg50ew8+7+NrXBFW0dPQqwf4Y9sR/j6jnA7OZGJ4= Date: Wed, 6 Jan 2021 12:42:23 -0800 From: Andrew Morton To: Hugh Dickins Cc: Andrea Arcangeli , Alex Shi , Minchan Kim , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mmap: replace if (cond) BUG() with BUG_ON() Message-Id: <20210106124223.587b93e5fdfd6a1a5f799c16@linux-foundation.org> In-Reply-To: References: <1607743586-80303-1-git-send-email-alex.shi@linux.alibaba.com> <1607743586-80303-2-git-send-email-alex.shi@linux.alibaba.com> <20210106114620.5c221690f3a9cad7afcc3077@linux-foundation.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: On Wed, 6 Jan 2021 12:18:36 -0800 (PST) Hugh Dickins wrote: > On Wed, 6 Jan 2021, Andrea Arcangeli wrote: > > > > I'd be surprised if the kernel can boot with BUG_ON() defined as "do > > {}while(0)" so I guess it doesn't make any difference. > > I had been afraid of that too, when CONFIG_BUG is not set: > but I think it's actually "if (cond) do {} while (0)". Yes, that is so. The thinking being that in most cases the compiler will be smart enough to avoid generating any code for `cond' anyway.