linux-kernel - Re: [PATCH] mm/mmap: replace if (cond) BUG() with BUG

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Date:   Wed, 6 Jan 2021 11:46:20 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Alex Shi <alex.shi@...ux.alibaba.com>,
        Minchan Kim <minchan@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/mmap: replace if (cond) BUG() with BUG_ON()

On Tue, 5 Jan 2021 20:28:27 -0800 (PST) Hugh Dickins <hughd@...gle.com> wrote:

> Alex, please consider why the authors of these lines (whom you
> did not Cc) chose to write them without BUG_ON(): it has always
> been preferred practice to use BUG_ON() on predicates, but not on
> functionally effective statements (sorry, I've forgotten the proper
> term: I'd say statements with side-effects, but here they are not
> just side-effects: they are their main purpose).
> 
> We prefer not to hide those away inside BUG macros

Should we change that?  I find BUG_ON(something_which_shouldnt_fail())
to be quite natural and readable.

As are things like the existing

BUG_ON(mmap_read_trylock(mm));
BUG_ON(wb_domain_init(&global_wb_domain, GFP_KERNEL));

etc.


No strong opinion here, but is current mostly-practice really
useful?