linux-kernel - Re: [PATCH] mm: Use BUG_ON instead of if condition followed by BUG

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Message-ID: <YZ7SJ8sXtXF4lZ4L@casper.infradead.org>
Date:   Thu, 25 Nov 2021 00:00:39 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     cgel.zte@...il.com
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, chiminghao <chi.minghao@....com.cn>,
        Zeal Robot <zealci@....com.cn>,
        Julia Lawall <julia.lawall@...6.fr>,
        Michal Marek <mmarek@...e.com>
Subject: Re: [PATCH] mm: Use BUG_ON instead of if condition followed by BUG

On Wed, Nov 24, 2021 at 01:23:42PM +0000, Matthew Wilcox wrote:
> On Wed, Nov 24, 2021 at 03:08:49AM +0000, cgel.zte@...il.com wrote:
> > From: chiminghao <chi.minghao@....com.cn>
> > 
> > Fix the following coccinelle report:
> > ./mm/memory_hotplug.c:2210:2-5:
> > WARNING  Use BUG_ON instead of if condition followed by BUG.
> 
> What coccinelle script is reporting this?

Maybe I found it?

scripts/coccinelle/misc/bugon.cocci:msg="WARNING: Use BUG_ON instead of if condition followed by BUG.\nPlease make sure the condition has no side effects (see conditional BUG_ON definition in include/asm-generic/bug.h)"

Julia, Michal, can we delete this script, please?  It's being abused.

> > -	if (try_remove_memory(start, size))
> > -		BUG();
> > +	BUG_ON(try_remove_memory(start, size));
> 
> I really, really, really do not like this.  For functions with
> side-effects, this is bad style.  If it's a pure predicate, then
> sure, but this is bad.
>