linux-kernel - Re: [PATCH v2] kernel/module: Use BUG_ON instead of if condition followed by BUG

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Message-ID: <YJ4ysIDqL9WWg3ZI@p200300cbcf361a0029e37a38368d6727.dip0.t-ipconnect.de>
Date:   Fri, 14 May 2021 10:20:00 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     zhouchuangao <zhouchuangao@...o.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kernel/module: Use BUG_ON instead of if condition
 followed by BUG

+++ zhouchuangao [12/05/21 07:01 -0700]:
>Fix the following coccinelle report:
>
>kernel/module.c:1018:2-5:
>WARNING: Use BUG_ON instead of if condition followed by BUG.
>
>BUG_ON uses unlikely in if(). Through disassembly, we can see that
>brk #0x800 is compiled to the end of the function.
>As you can see below:
>    ......
>    ffffff8008660bec:   d65f03c0    ret
>    ffffff8008660bf0:   d4210000    brk #0x800
>
>Usually, the condition in if () is not satisfied. For the
>multi-stage pipeline, we do not need to perform fetch decode
>and excute operation on brk instruction.
>
>In my opinion, this can improve the efficiency of the
>multi-stage pipeline.
>
>Signed-off-by: zhouchuangao <zhouchuangao@...o.com>

Thanks for fixing the changelog. Queued on modules-next.

Jessica