Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 6 Jan 2021 12:42:23 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Hugh Dickins <hughd@google.com>
Cc:     Andrea Arcangeli <aarcange@redhat.com>,
        Alex Shi <alex.shi@linux.alibaba.com>,
        Minchan Kim <minchan@kernel.org>,
        Michal Hocko <mhocko@suse.com>, 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: <alpine.LSU.2.11.2101061213540.2492@eggly.anvils>
References: <1607743586-80303-1-git-send-email-alex.shi@linux.alibaba.com>
        <1607743586-80303-2-git-send-email-alex.shi@linux.alibaba.com>
        <e50574aa-87b8-8ddf-2235-ef98e22bcb7d@linux.alibaba.com>
        <alpine.LSU.2.11.2101051919130.1361@eggly.anvils>
        <20210106114620.5c221690f3a9cad7afcc3077@linux-foundation.org>
        <X/YY+mjpq15nmryI@redhat.com>
        <alpine.LSU.2.11.2101061213540.2492@eggly.anvils>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Wed, 6 Jan 2021 12:18:36 -0800 (PST) Hugh Dickins <hughd@google.com> 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.